Methods and systems for event-modulated electron microscopy

Abstract

A method for measuring an electronic signal or an electronically induced signal may be provided. The method may include the step of providing a threshold number of events or a threshold event rate for a pixel on a detector. The method may include the step of collecting a threshold number of events or determining that a threshold event rate has been achieved from the detector, where the signal in the detector is an electronic signal or an electronically induced signal from a sample. The method may, in response, include the step of modulating the intensity of an electron source directed to the sample.

Description

Background Art

[0001] (Cross - reference to related applications) This application claims the benefit of U.S. Application No. 18 / 104,101, filed on January 31, 2023, and U.S. Application No. 18 / 383,422, filed on October 24, 2023, which are hereby incorporated by reference in their entireties.

[0002] In a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), an electron - beam focusing probe can be rastered across a sample. The interaction between the electron beam and the sample material can produce a wide variety of signals, which can then be captured individually or collectively to produce an image. Still other signals can contain chemical, bonding, electron, diffraction, or some other data. This data can be measured point - by - point as the beam is rastered. However, the electron beam intended to measure the properties of the sample can change the sample and even damage the sample.

Summary of the Invention

Means for Solving the Problems

[0003] The applicant recognizes an unmet need for new methods and systems for maintaining the electron signal from a sample while reducing the impact of electron dose on the sample. Reducing the dose rate incident on the sample (e.g., electron beam) reduces sample damage, but the signal is also reduced, provided all other variables are kept constant. The systems and methods disclosed herein may employ an electron dose modulator with an arbitrary trigger signal in combination with a digital detector with a “fast” response rate. The digital detector with a fast response rate may detect individual electron collision events using the steep rising edge accompanying the arrival of electrons at the detector. Using both the dose modulator and the event detector, the systems and methods of this disclosure may be able to switch the electron beam with precise control (e.g., about 10 nanoseconds). The control over beam switching may allow blanking of the electron beam once sufficient information (or even a single event) has been detected. For example, once sufficient information has been collected at each pixel, the beam may be stopped and data acquisition may proceed to the next pixel.

[0004] In one aspect, the present invention provides a method for measuring an electronic signal or an electronically induced signal. The method may include (a) providing a threshold number of events or a threshold event rate with respect to an element or part of a detector; (b) collecting a threshold number of events or determining that a threshold event rate has been achieved from the detector, wherein the signal in the detector is an electronic signal or an electronically induced signal from a sample; and (c) modulating the intensity of an electron source or ion source directed to a sample in response to the collecting step in (b).

[0005] In some embodiments, (c) includes the step of moving the electron source or ion source to a different location on the sample. In some embodiments, (c) includes the step of turning off the electron source or ion source. In some embodiments, (c) includes the step of deflecting the path of the electron source or ion source. In some embodiments, (c) is performed substantially in real time. In some embodiments, real time includes substantially within the electron counting interval of the detector. In some embodiments, (c) is performed within the electron counting interval of the detector. In some embodiments, the threshold number of events or threshold event rate is determined based at least in part on information about the sample.

[0006] In some embodiments, (c) includes the step of modulating an electron or ion dose waveform, the electron dose waveform being continuously updated based on the number of events determined from the signal. In some embodiments, the electron or ion dose waveform has a continuously variable time profile. In some embodiments, the electron or ion dose waveform has an arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the method further includes the step of receiving an indication of the arbitrarily defined time profile from a user. In some embodiments, the electron or ion dose waveform has a series of intermediate points. In some embodiments, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some embodiments, the series of intermediate points has more than 1,000 intermediate points.

[0007] In some embodiments, the method further includes recording the time to achieve a threshold number of events or a threshold event rate in an element or part of the detector. In some embodiments, the method further includes forming an image based at least partially on the time to achieve a threshold number of events or a threshold event rate with respect to multiple elements or parts of the detector. In some embodiments, the method further includes collecting a threshold number of events from the detector or determining that a threshold event rate has been achieved, wherein the signal in the detector is an electron or ion signal or an electron-induced or ion-induced signal from or through a sample.

[0008] In some embodiments, the method further includes, following (c), providing a threshold number of events or threshold event rate with respect to a second element or second part of the detector.

[0009] In another aspect, a method for forming an image based on an electronic event signal is provided. This method may include the steps of (a) providing a threshold number of events or a threshold event rate for a first element or part of a detector, and (b) recording the time to achieve a threshold number of events or a threshold event rate for a second element or part of the detector.

[0010] In some embodiments, the second element or part is an element or part. In some embodiments, the second element or part is another element or part. In some embodiments, the method further includes the step of forming an image based at least partially on the time to achieve a threshold number of events or threshold event rate with respect to a plurality of elements or parts of the detector. In some embodiments, the signal in the detector is an electronic signal or an electron-induced signal from a sample. In some embodiments, the electronic signal or electron-induced signal is a single electronic signal.

[0011] In some embodiments, the method further includes (c) a step of collecting a threshold number of events or a threshold event rate from a detector. In some embodiments, the method further includes (d) a step of modulating the intensity of an electron source or ion source directed to the sample in response to the collecting step in (c). In some embodiments, (d) includes a step of moving the electron source to a different location on the sample. In some embodiments, (d) includes a step of turning off the electron source or ion source. In some embodiments, (d) includes the use of a deflector. In some embodiments, (d) is performed substantially in real time. In some embodiments, real time includes substantially within the event counting interval of the detector. In some embodiments, the threshold number of events or threshold event rate is determined based on information about the sample.

[0012] In some embodiments, (d) includes the step of modulating an electron or ion dose waveform, the electron dose waveform being continuously updated based on the number of events determined from the signal. In some embodiments, the electron or ion dose waveform has a continuously variable time profile. In some embodiments, the electron or ion dose waveform has an arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the method further includes the step of receiving an indication of the arbitrarily defined time profile from a user. In some embodiments, the electron or ion dose waveform has a series of intermediate points. In some embodiments, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some embodiments, the series has more than 1,000 intermediate points.

[0013] In another aspect, the present disclosure provides a method for forming an image based on an electronic event signal. The method may include (a) providing an information threshold for a sample; (b) collecting a number of events equal to the information threshold from a detector or determining that an event rate equal to the information threshold has been achieved, wherein the signal in the detector is an electronic signal or an electronically induced signal from the sample; and (c) forming an image based at least in part on the electronic signal or the electronically induced signal.

[0014] In some embodiments, the information threshold for a sample is based on the sum of the total electronic counts across the sample. The information threshold may be a mutual information threshold. In some embodiments, the electronic signal or electronically induced signal is a single electronic signal. In some embodiments, the method further includes the step of recording the time to achieve a threshold number of events or threshold event rate at a pixel.

[0015] In some embodiments, the method further includes a step of modulating the intensity of an electron or ion source directed to the sample in response to the collecting step in (d)(b). In some embodiments, (d) includes a step of moving the electron or ion source to a different location on the sample. In some embodiments, (d) includes a step of turning off the electron or ion source. In some embodiments, (d) includes the use of a deflector. In some embodiments, (d) is performed substantially in real time. In some embodiments, real time includes substantially within the electron counting interval of the detector. In some embodiments, the threshold number of events or threshold event rate is determined based on information about the sample.

[0016] In some embodiments, (d) includes the step of modulating an electron or ion dose waveform, the electron dose waveform being continuously updated based on the number of events determined from the signal. In some embodiments, the electron or ion dose waveform has a continuously variable time profile. In some embodiments, the electron or ion dose waveform has an arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the method further includes the step of receiving an indication of the arbitrarily defined time profile from a user. In some embodiments, the electron or ion dose waveform has a series of intermediate points. In some embodiments, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some embodiments, the series has more than 1,000 intermediate points.

[0017] In another aspect, the Disclosure provides a method for measuring an electronic signal or an electronically induced signal. The method may include the steps of (a) providing a pattern generator configured to produce an electrical signal representing an electronic or ion dose waveform having a continuously variable time profile, and (b) providing an event signal processor configured to receive and respond to an electronic signal or an electronically induced signal from a detector, and to determine the number of electronic events on the detector based on the rising edge of the electronic signal or an electronically induced signal in the detector, wherein the event signal processor has a single event resolution.

[0018] In some embodiments, the method further includes the step of modulating an electron / ion signal based on the number of electron events. In some embodiments, the method further includes the step of carrying out any aspect or embodiment of the method.

[0019] In another aspect, the Disclosure provides a device comprising a controller, the controller comprising a non-transient storage medium on which instructions are stored, the instructions being configured to, when executed by the controller, carry out a method of any aspect or embodiment.

[0020] In another aspect, the present disclosure provides a device. The device may comprise: a deflector positioned between an electron source or ion source and a sample area, which modulates the intensity of the electron source or ion source directed to the sample area according to an electron or ion dose waveform having a continuously variable time profile; a detector configured to receive an electron signal or electron-induced signal associated with the sample area, wherein an electron event on the detector is correlated to the rising edge of the electron signal or electron-induced signal in the detector; and a controller operably coupled to the deflector and the detector, which is configured to determine a continuously variable time profile in response to an electron event.

[0021] In some embodiments, the controller comprises one or more field-programmable gate arrays. In some embodiments, the device further comprises a first field-programmable gate array configured to control a deflector. In some embodiments, the device further comprises a first field-programmable gate array configured to control a detector. In some embodiments, the device further comprises an event signal processor configured to receive and respond to an electronic signal or an electronically induced signal from the detector, and to determine the number of electronic events on the detector based on the rising edge of the electronic signal or electronically induced signal at the detector.

[0022] In some embodiments, the event signal processor is part of the controller. In some embodiments, the event signal processor is separate from the controller. In some embodiments, the event signal processor has a single event resolution. In some embodiments, the event signal processor is configured to determine the gradient of an electronic signal or an electronically induced signal. In some embodiments, an electronic event is correlated with the gradient exceeding a threshold gradient value.

[0023] In some embodiments, the device further comprises a scintillator, the scintillation signal being generated in response to an electronic signal or an electronically induced signal, and the event signal processor is configured to receive the scintillation signal. In some embodiments, the event signal processor comprises an output signal, the output signal being operably coupled to a controller for determining a continuously variable time profile. In some embodiments, the output signal is an instantaneous trigger signal.

[0024] In some embodiments, the controller is configured to determine the time to keep an electronic event signal on in response to an electronic event signal. In some embodiments, the continuously variable time profile is modulated in "real time". In some embodiments, "real time" substantially includes within the electronic counting interval of the detector. In some embodiments, the detector comprises multiple detectors or detector segments. In some embodiments, the detector comprises an image sensor. In some embodiments, the detector comprises a single-channel detector. In some embodiments, the detector is a multi-channel detector. In some embodiments, the device is configured to detect in parallel from multiple channels.

[0025] In some embodiments, the waveform comprises a series of intermediate points. In some embodiments, the series comprises more than 1,000 intermediate points. In some embodiments, the electron or ion dose waveform comprises an arbitrarily defined time profile. In some embodiments, the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the arbitrarily defined time profile is indicated by the user.

[0026] In some embodiments, the deflector comprises a drive electrode and an electrode at a fixed voltage. In some embodiments, the deflector comprises two drive electrodes. In some embodiments, the electron or ion dose waveform modulates the average intensity of the electron or ion source directed toward the sample area. In some embodiments, the average intensity is modulated substantially without changes to other imaging conditions. In some embodiments, the average intensity is controllable independently of the drive voltage of the electron or ion source. In some embodiments, the average intensity is continuously variable over a dose transmission range of 0 to 100%. In some embodiments, the electron or ion dose waveform comprises a periodic waveform. In some embodiments, the electron or ion dose waveform is non-periodic. In some embodiments, the electron or ion dose waveform comprises a pump pulse and a probe pulse.

[0027] In some embodiments, the electron or ion dose waveform is a square wave. In some embodiments, the transition time between high and low voltage is less than about 50 nanoseconds, defined as the sum of ringing time and slope time. In some embodiments, the transition time between high and low voltage is less than about 10 nanoseconds (ns), defined as the slope time of the transition voltage from about 10% to about 90%. In some embodiments, the pulse width of the square wave is non-periodic. In some embodiments, the electron or ion dose waveform has a minimum exposure time of about 100 nanoseconds.

[0028] In some embodiments, the device further comprises a pattern generator configured to produce an electrical signal representing an electron or ion dose waveform, and driver electronics configured to receive the electrical signal from the pattern generator and supply a voltage comprising the electron or ion dose waveform to a deflector. In some embodiments, the device further comprises one or more computer processors comprising instructions that, when executed, receive an indication of an electron or ion dose waveform and deliver the indication to the pattern generator.

[0029] In another aspect, the present disclosure provides a method for measuring an electronic signal or an electron-induced signal, comprising providing a device of any aspect or embodiment.

[0030] In some embodiments, the number or rate of threshold events is an information threshold. The information threshold can be a mutual information threshold.

[0031] In another aspect, the present disclosure provides a method for measuring an electronic signal or an electron-induced signal. The method may include (a) providing an information threshold for an element or portion of a detector; (b) determining that the information threshold is achieved, wherein the signal in the detector is an electronic signal or an electron-induced signal from a sample; and (c) modulating the intensity of an electron source or ion source directed at the sample in response to the determination in (b). In some embodiments, the information threshold may be a mutual information threshold.

[0032] In some embodiments, the method further comprises providing a device of any aspect or embodiment.

[0033] In some embodiments, (c) includes the step of moving the electron source or ion source to a different location on the sample. In some embodiments, (c) includes the step of turning off the electron source or ion source. In some embodiments, (c) includes the use of a deflector. In some embodiments, (c) is performed substantially in real time. In some embodiments, real time includes substantially within the electron counting interval of the detector.

[0034] In another aspect, the Disclosure provides a method for measuring an electronic signal or an electron-induced signal. The method may include (a) providing a logical condition relating to one or more measurements from an element, pixel, or part of a detector, wherein the one or more measurements comprise an event count measurement of an electronic or ion signal or an electron-induced or ion-induced signal; (b) determining whether the logical condition is met, at least in part, based on the one or more measurements; and (c) modulating the intensity of an electron or ion source directed to a sample in response to the determination in (b).

[0035] In some embodiments, a logical condition comprises one or a combination of event conditions. In some embodiments, one or a combination of event conditions comprises one or more threshold event counts. In some embodiments, one or a combination of event conditions comprises a threshold event rate. In some embodiments, one or a combination of event conditions comprises the absence of an event after a certain time period. In some embodiments, one or a combination of event conditions comprises measurements in multiple detectors or regions of detectors. In some embodiments, one or a combination of event conditions comprises multiple threshold event conditions, where each measurement in multiple detectors or regions of detectors comprises an associated threshold condition of the multiple threshold conditions. In some embodiments, one or a combination of event conditions comprises a comparison of measurements between multiple detectors or regions of detectors. In some embodiments, one or a combination of event conditions varies with position on the sample. In some embodiments, one or a combination of event conditions comprises an event or a measurement of an event. In some embodiments, one or a combination of event conditions comprises a mutual information threshold. In some embodiments, one or a combination of event conditions comprises an experimental signal. In some embodiments, the experimental signal is used to induce modulation in (c). In some embodiments, modulation is induced with a latency relative to a pixel residence time of less than 20 nanoseconds. In some embodiments, modulation is induced with a latency relative to a pixel residence time of less than 50 nanoseconds. In some embodiments, modulation is induced with a latency relative to a pixel residence time of less than 100 nanoseconds. In some embodiments, the experimental signal includes a user-defined input. In some embodiments, the user-defined input includes a probe pulse or a pump pulse.

[0036] In some embodiments, (c) further includes the step of moving the electron source or ion source to a different location on the sample. In some embodiments, (c) further includes the step of turning off the electron source or ion source. In some embodiments, (c) further includes the step of deflecting the path of the electron source or ion source. In some embodiments, (c) is performed substantially in real time. In some embodiments, (c) is performed within the electron counting interval of the detector.

[0037] In some embodiments, (c) further includes the step of modulating an electron or ion dose waveform based at least in part on one or more measurements. In some embodiments, the electron or ion dose waveform has a continuously variable time profile. In some embodiments, the electron or ion dose waveform has an arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the method further includes the step of receiving an indication of the arbitrarily defined time profile from a user. In some embodiments, the electron or ion dose waveform has a series of intermediate points. In some embodiments, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some embodiments, the series of intermediate points has more than 1,000 intermediate points.

[0038] In some embodiments, the method further includes recording the time it takes for a logical condition to be met in a pixel, element, or portion of the detector. In some embodiments, the method further includes collecting a determination of whether the logical condition is met, where the electron or ion signal or electron-induced or ion-induced signal is from or through the sample.

[0039] In another aspect, the present disclosure provides a device. The device may comprise: a deflector positioned between an electron source or ion source and a sample area, which modulates the intensity of the electron source or ion source directed towards the sample area according to an electron or ion dose waveform having a continuously variable time profile; a detector configured to receive an electron signal or electron-induced signal associated with the sample area; and a controller operably coupled to the deflector and the detector, which is configured at least in part to determine the continuously variable time profile in response to the electron signal or electron-induced signal based on a logical condition. In some embodiments, the logical condition comprises one or a combination of event conditions. In some embodiments, one or a combination of event conditions comprises one or more threshold event numbers. In some embodiments, one or a combination of event conditions comprises a threshold event rate. In some embodiments, one or a combination of event conditions comprises the absence of an event after a certain time period. In some embodiments, one or a combination of event conditions comprises measurements in multiple detectors or regions of detectors. In some embodiments, one or a combination of event conditions comprises multiple threshold event conditions, and each measurement comprises an associated threshold condition of the multiple threshold conditions. In some embodiments, one or a combination of event conditions comprises a comparison of measurements between multiple detectors or regions of detectors. In some embodiments, one or a combination of event conditions varies with position on the sample. In some embodiments, one or a combination of event conditions comprises an event or a measurement of an event. In some embodiments, one or a combination of event conditions comprises an experimental signal.

[0040] In some embodiments, the experimental signal is used to induce modulation in (c). In some embodiments, the modulation is induced with a latency relative to a pixel residence time of less than 20 nanoseconds. In some embodiments, the modulation is induced with a latency relative to a pixel residence time of less than 50 nanoseconds. In some embodiments, the modulation is induced with a latency relative to a pixel residence time of less than 100 nanoseconds. In some embodiments, the experimental signal comprises a user-defined input. In some embodiments, the user-defined input comprises a probe pulse or a pump pulse.

[0041] In some embodiments, the controller comprises one or more field-programmable gate arrays. In some embodiments, the device further comprises a first field-programmable gate array configured to control a deflector. In some embodiments, the device further comprises a first field-programmable gate array configured to control a detector.

[0042] In some embodiments, the device further includes an event signal processor configured to receive and respond to an electronic signal or electronically induced signal from a detector to determine whether a logical condition is met. In some embodiments, the event signal processor is part of the controller. In some embodiments, the event signal processor is separate from the controller. In some embodiments, the event signal processor has a single event resolution. In some embodiments, the event signal processor has an output signal, which is operably coupled to the controller to determine a continuously variable time profile. In some embodiments, the output signal is an instantaneous trigger signal. In some embodiments, the continuously variable time profile is modulated in real time. In some embodiments, the continuously variable time profile is modulated within the electronic counting interval of the detector.

[0043] In some embodiments, the detector comprises multiple detectors or detector segments. In some embodiments, the detector comprises an image sensor. In some embodiments, the detector comprises a single-channel detector. In some embodiments, the detector is a multi-channel detector. In some embodiments, the device is configured to detect in parallel from multiple channels.

[0044] In some embodiments, the electron or ion dose waveform comprises a series of intermediate points. In some embodiments, the series of intermediate points comprises more than 1,000 intermediate points. In some embodiments, the electron or ion dose waveform comprises an arbitrarily defined time profile. In some embodiments, the waveform comprises a series of intermediate points, which can be selected individually or collectively to construct an arbitrarily defined time profile. In some embodiments, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some embodiments, the arbitrarily defined time profile is indicated by the user.

[0045] In some embodiments, the deflector comprises a driving electrode and an electrode at a fixed voltage. In some embodiments, the deflector comprises two driving electrodes. In some embodiments, the electron or ion dose waveform modulates the average intensity of the electron or ion source directed toward the sample area. In some embodiments, the average intensity is modulated substantially without changing other imaging conditions. In some embodiments, the average intensity is controllable independently of the driving voltage of the electron or ion source. In some embodiments, the average intensity is continuously variable over a dose transmission range of 0 to 100%.

[0046] In some embodiments, the electron or ion dose waveform has a periodic waveform. In some embodiments, the electron or ion dose waveform is aperiodic. In some embodiments, the electron or ion dose waveform comprises a pump pulse and a probe pulse. In some embodiments, the electron or ion dose waveform is a square wave. In some embodiments, the transition time between high and low voltage is less than about 50 nanoseconds (ns), defined as the sum of ringing time and slope time. In some embodiments, the transition time between high and low voltage is less than about 10 nanoseconds (ns), defined as the slope time of the transition voltage from about 10% to about 90%. In some embodiments, the pulse width of the square wave is aperiodic. In some embodiments, the electron or ion dose waveform has a minimum exposure time of about 100 nanoseconds (ns).

[0047] In some embodiments, the device further comprises a pattern generator configured to produce an electrical signal representing an electron or ion dose waveform, and driver electronics configured to receive the electrical signal from the pattern generator and supply a voltage having an electron or ion dose waveform to a deflector.

[0048] In some embodiments, the device further comprises one or more computer processors, which, when executed, are configured to receive an indication of an electron or ion dose waveform and deliver the indication to a pattern generator, and which have instructions.

[0049] In another aspect, the present application provides a non-transient computing device-readable medium for storing instructions executable by a processor to cause a computing device to carry out a method. The method may include the steps of (a) receiving a condition code; (b) receiving a signal corresponding to an electronic signal or an electronically induced signal from a sample; (c) comparing the received signal with a condition code; and (d) determining whether an output signal should be transmitted, at least in part, based on the comparison performed in (c). In some embodiments, the condition code comprises a reference to a lookup table describing a set of logical conditions. In some embodiments, the condition code comprises a set of logical conditions. In some embodiments, the logical condition comprises one or a combination of event conditions. In some embodiments, one or a combination of event conditions comprises one or more threshold event counts. In some embodiments, one or a combination of event conditions comprises a threshold event rate. In some embodiments, one or a combination of event conditions comprises the absence of an event after a certain time period. In some embodiments, one or a combination of event conditions comprises measurements in a plurality of detectors or regions of detectors. In some embodiments, one or a combination of event conditions comprises multiple threshold event conditions, and each measurement comprises an associated threshold condition of the multiple threshold conditions. In some embodiments, one or a combination of event conditions comprises a comparison of measurements between multiple detectors or regions of detectors. In some embodiments, one or a combination of event conditions varies with position on the sample. In some embodiments, one or a combination of event conditions comprises an event or a measurement of an event.

[0050] In some embodiments, the output signal includes a trigger signal. In some embodiments, the trigger signal includes a latency relative to a pixel residence time of less than 20 nanoseconds. In some embodiments, modulation is induced with a latency relative to a pixel residence time of less than 50 nanoseconds. In some embodiments, modulation is induced with a latency relative to a pixel residence time of less than 100 nanoseconds.

[0051] Another aspect of this disclosure provides a system comprising one or more computer processors. In some cases, the system comprises one or more computer processors and computer memory coupled thereto. The computer memory comprises machine-executable code that, in response to execution by one or more computer processors, implements any of the methods described above or elsewhere in this specification.

[0052] Another aspect of this disclosure provides a system comprising a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). The FPGA or ASIC comprises programmable logic blocks, programmable interconnects, etc., configured to implement any of the methods described above or elsewhere herein. The system may comprise one or more computer processors and computer memory coupled thereto. The one or more computer processors may be configured to provide information to the FPGA or ASIC in order to implement any of the methods described above or herein.

[0053] Additional aspects and advantages of this disclosure will be readily apparent to those skilled in the art from the following detailed description, which shows and describes only illustrative embodiments of this disclosure. As will be recognized, other different embodiments are possible, and some of their details can be modified in various obvious ways without departing from this disclosure. Therefore, the drawings and description are intended to be illustrative and not restrictive in nature.

[0054] (Integrated by reference) All publications, patents, and patent applications referenced herein are incorporated herein by reference to the same extent as each individual publication, patent, or patent application is shown to be incorporated by specific and individual reference. With respect to any extent that publications and patents or patent applications incorporated by reference conflict with the disclosures contained herein, this specification is intended to take precedence and / or supersede any such conflicting material. [Brief explanation of the drawing]

[0055] Novel features of the present invention are described in detail in the appended claims. A deeper understanding of the features and advantages of the present invention will be obtained by referring to the following detailed description, which describes illustrative embodiments in which the principles of the present invention are utilized, and to the accompanying drawings (also referred to herein as "Figure" and "FIG.").

[0056] [Figure 1A] Figure 1A schematically illustrates a device for collecting electronic signals according to this disclosure.

[0057] [Figure 1B] Figure 1B schematically illustrates scanning transmission electron microscopes according to several embodiments.

[0058] [Figure 2] Figure 2 illustrates an embodiment of the event signal processor 150 of the present disclosure.

[0059] [Figure 3-1] Figure 3A illustrates exemplary single-electron collision event traces in several embodiments.

[0060] [Figure 3-2] Figures 3B-3D show the analog signal, the signal from the event process, and the signal (intensity) on the pixel (vertical) line as a function of time (horizontal) for each combination of the two.

[0061] [Figure 4] Figure 4 illustrates an embodiment using variable blanking, enabled by an electrostatic dose modulator driven by an arbitrary trigger signal.

[0062] [Figure 5] Figure 5 shows the representation of cumulative and incremental mutual information regarding consecutive electron detection events.

[0063] [Figure 6] Figure 6 shows an exemplary method for measuring an electronic signal or an electronically induced signal.

[0064] [Figure 7] Figure 7 shows a histogram of the ADF signal rate (relative probability) per pixel as a function of the scattering rate for an exemplary sample.

[0065] [Figure 8] Figure 8 shows an exemplary method for forming an image based on electronic event signals.

[0066] [Figure 9] Figure 9 shows another exemplary method for forming an image based on electronic event signals.

[0067] [Figure 10] Figure 10 shows another exemplary method for measuring an electronic signal or an electronically induced signal.

[0068] [Figure 11] Figure 11 shows a computer system programmed or otherwise configured to implement the method provided herein.

[0069] [Figure 12] Figure 12 shows another exemplary method for measuring an electronic signal or an electronically induced signal.

[0070] [Figure 13] Figure 13 shows an example of a method that can be performed by a processor to measure an electronic signal. [Modes for carrying out the invention]

[0071] (Detailed explanation) Various embodiments of the present invention are shown and described herein, but it will be apparent to those skilled in the art that such embodiments are provided only as examples. Numerous modifications, alterations, and substitutions can be conceived by those skilled in the art without departing from the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be adopted.

[0072] The systems and methods disclosed herein may utilize event-driven beam blanking to improve information harvesting per electron in electron imaging systems, such as STEM and SEM. An electronic device may monitor signals from a counting detector or a plurality of such detectors during the pixel residence time. If the signal detected during the pixel residence time exceeds one or more predetermined thresholds, the beam may be stopped for the remainder of the residence time. Optionally (when using a scanning controller that assists an input pixel clock signal, e.g., a “triggerable” controller), a signal is transmitted at this point to accelerate the transition to the next pixel. The ratio of the number of electrons detected to the beam-on duration for that pixel is then an unbiased estimator of the total signal that might have been detected if the electron beam had remained on for the entire residence time. This can be used to generate a high-quality image or set of images in real time that is qualitatively similar to an image obtained by other methods, but with substantially reduced radiation damage to the sample. In the case of a triggerable scanning controller, the acquisition time can also be substantially reduced.

[0073] The threshold may be as simple as turning off the beam after detecting a specified number of electrons n (including the very simple case where n=1) on a single detector, or it may be adaptive, or it may involve a set of rules. For example, the rules may involve various detection rates on multiple detectors or detector segments.

[0074] The advantage of this disclosure is that it recognizes that diminishing returns to information may exist. More information per electron may exist for earlier electrons. Therefore, it may be advantageous to determine when a sufficient amount of information has been obtained and move on, rather than collecting data over a long duration on a single spot. From a device construction perspective, single-electron counting combined with continuous dose modulation may enable the cessation of dose irradiation in response to real-time data.

[0075] Definitions: Unless otherwise defined, all technical terms used herein have the same meaning as those commonly understood by those skilled in the art in which this disclosure pertains.

[0076] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include multiple references unless the context clearly determines otherwise. Any reference to “or” herein is intended to include “and / or” unless otherwise stated.

[0077] As used herein, unless otherwise specified, the terms “about” or “approximately” mean an acceptable error in relation to a particular value as determined by a person skilled in the art, which depends in part on the method by which the value is measured or determined. In some cases, the terms “about” or “approximately” mean within 1, 2, 3, or 4 standard deviations. In other cases, the terms “about” or “approximately” mean within 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or 0.05% of a given value or range. In some cases, the term “about” refers to a number ± 10% of that number. In other cases, when used in the context of a range, the term “about” refers to that range between minus 10% of its lowest value and plus 10% of its highest value.

[0078] Whenever the terms “at least,” “greater than,” or “greater than or equal to” precede the first number in a set of two or more numbers, the terms “at least,” “greater than,” or “greater than or equal to” apply to each of the numbers in that set. For example, “greater than or equal to 1, 2, or 3” is equivalent to “greater than or equal to 1,” “greater than or equal to 2,” or “greater than or equal to 3.”

[0079] Whenever the terms “less than or equal to,” “less than,” or “less than or equal to” precede the first number in a set of two or more numbers, the terms “less than,” “less than,” or “less than or equal to” apply to each of the numbers in that set. For example, less than or equal to 3, 2, or 1 is equivalent to less than or equal to 3, less than or equal to 2, or less than or equal to 1.

[0080] Some embodiments of the present invention described herein assume a numerical range. When a range exists, the range includes its endpoints. In addition, all subranges and values ​​within the range exist as if they were explicitly written out.

[0081] As disclosed herein, the term “cross-section” generally refers to the scattering cross-section. The cross-section generally does not refer to the geometric cross-section, but rather to the effective area with respect to the collision. The cross-section represents the probability of scattering from a sample within the associated interaction time. This may be expressed mathematically in units of area. Electron imaging system

[0082] Figure 1A schematically illustrates a device for collecting electronic signals according to this disclosure. The device may be an imaging device. The device may be a device for collecting electronic event signals. The device may be an electron microscope. For example, the device may comprise a scanning transmission electron microscope. For example, the device may comprise an electron beam lithograph. In some cases, the device may be a device for collecting ion event signals. For example, the device may comprise a focused ion beam directed at a sample or a helium ion beam directed at a sample. In some cases, the device may include an annular dark-field (ADF) electron detector, thereby implementing annular dark-field scanning transmission electron microscopy (ADF-STEM). However, systems such as those disclosed herein may be used in conjunction with other electron microscopy and electron spectroscopy applications such as serial section electron microscopy (sSEM), scanning electron microscopy (SEM), backscattered electron microscopy (REM), scanning transmission electron microscopy (STEM), and transmission electron microscopy (TEM). Many of the above are instruments capable of performing more than one of these operating modes. Furthermore, there are geometric variations in which the electron or ion source may be located at the bottom or on the side of the instrument, and the beam may propagate upward or horizontally. The various techniques described above may employ a variety of sensing modalities, including one or more of low-dose imaging, digital electronic counting, electrostatic dose modulation (EDM), or compressed sensing (CS), or adaptive subsampling, or non-raster scanning patterns, or any combination thereof.

[0083] Various examples of high-resolution scanning transmission electron microscopy are provided in "High-Resolution Scanning Transmission Electron Microscopy (HRSTEM) Techniques: High-Resolution Imaging and Spectroscopy Side by Side" by DG Stroppa, LF Zagonel, LA Montoro, ER Leite, and AJ Ramirez, ChemPhysChem (which is incorporated herein by reference as a whole).

[0084] As shown, device 100 may comprise an electron source 102, a deflector 106, an aperture 108, a sample 110, and a detector 104. Device 100 may also comprise various analog or digital electronic components. These electronic components may comprise, for example, a drive electronics unit 120, a digital pattern generator 130, a sequence generation algorithm 140, an event signal processor 150, and a scanning controller 180.

[0085] In some cases, the device may be a STEM device. For example, the device may be an ADF-STEM device. In some cases, in an ADF-STEM, a sample that is at least partially transparent may be investigated using an electron beam. For example, the sample may be thin so that the sample is at least partially electron-transparent. In some cases, the electron beam may be focused by one or more electrostatic or electromagnetic lenses. As the incident beam (sometimes called the primary beam) passes through the sample, a small portion of this illumination may be scattered at a certain angle, for example, by so-called Rutherford scattering. This scattering may be collected using an annular detector placed beyond the sample. In some cases, an image may be created by rasterizing the electron beam across the sample. At each probe position in the raster, the total scattering intensity may be logged and represented at the same position in image coordinates. As the probe scans, the image may be built pixel by pixel. Areas of greater scattering (pixels) result in increased brightness in the image, while vacuum areas appear black (hence the name dark-field).

[0086] In some cases, irradiation may be delivered at a consistent rate (fixed electron beam current) over a consistent time (e.g., residence time) before moving the focused electron beam to a new pixel location and repeating the process. In other cases, the image of the recorded signal is displayed in arbitrary units, as this is sufficient for many qualitative studies.

[0087] Figure 1B schematically illustrates a scanning transmission electron microscope according to several embodiments. As shown, device 100' may comprise an electron gun G, one or more apertures A, one or more electrostatic lenses (e.g., one or more focusing lenses CL, one or more scanning lenses SL, one or more objective lenses OL, one or more projector lenses PL), a sample S, and one or more detectors (e.g., a bright-field detector BF, annular dark-field detector ADF, a high-angle annular dark-field detector HAADF, an X-ray detector XEDS, an electron energy loss spectrometer detector EELS, etc.). As shown, device 100' represents multiple detectors for multiple different image modalities.

[0088] Electron source: An electron source 102 may be provided, as shown in Figure 1A. The electron source may emit electrons at a controllable accelerating voltage. The electron source may emit electrons in the direction of the sample area. The electron source may include an electron gun (e.g., G in Figure 1B). The electron source may include a thermal filament source that emits electrons. The electron source may include an electric field emission source that emits electrons. The electron source may include one or more accelerating optical systems. For example, the accelerating optical system may include a cathode and an anode. The anode may include a controllable electrode voltage for accelerating electrons away from the filament at a selectable voltage. The electron source may include a set of electron optical systems for shaping the spatial profile of the electron source. For example, the electron source may include one or more electrostatic or electromagnetic lenses. One or more lenses may include, for example, one or more focusing lenses CL, one or more scanning lenses SL, one or more objective lenses OL, and one or more projector lenses PL, as shown in Figure 1B. A focusing lens may be used as the focus of the first step of electrons from the electron source, as disclosed herein. A scanning lens may assist, at least partially, in steering the electron source. Alternatively, the scanning lens may be used to adjust the focus of the lens as the electron source is scanned. In some cases, the device may not have a scanning lens, and the electron source may be steered primarily by a deflector. In some cases, the electron source may be directed toward the sample by one or more steering deflectors. The steering deflectors may also be used, or may not be used, to control the time profile of the electron dose waveform arriving at the sample area.

[0089] Electron deflector: As shown in Figure 1A, a detector 104 may be provided. The detector may receive electron signals propagating through the sample area or electron-induced signals from the sample area. The detector may be a two-dimensional detector array. In some cases, the two-dimensional detector array may consist of a single detector, e.g., a CCD or CMOS image sensor comprising a two-dimensional array of individual pixels or groups of pixels, or in some cases, a two-dimensional array of individual detectors, e.g., a two-dimensional array of CCD or CMOS image sensors. In some cases, the two-dimensional detector array may consist of a two-dimensional array of individual detectors, including a combination of CMOS image sensors, CCD image sensors, dark-field STEM detectors, Faraday cup sensors, or other types of detectors. In some cases, the detector may consist of an energy-dispersive X-ray spectrometer (EDS). An EDS detector may measure electron-induced signals. For example, an EDS detector may measure X-rays generated when an electron beam collides with the sample area. In some cases, X-rays can be generated when an electron beam collides with and interacts with the sample as it passes through the sample area.

[0090] Examples of suitable detectors for use in the disclosed methods and systems include, but are not limited to, charge-coupled device (CCD) image sensors and cameras including a layer that emits photons when struck by electrons, complementary metal-oxide-semiconductor (CMOS) image sensors and cameras including a layer that emits photons when struck by electrons, direct electron detection (EDD) image sensors and cameras (e.g., CCD, CMOS, or hybrid pixel image sensors designed to directly detect electrons), time-of-flight (ToF) image sensors and cameras, dark-field STEM detectors, Faraday cups, quad photodiodes, annular dark-field detectors, bright-field detectors, universal detectors, or any combination thereof.

[0091] One or more detectors may comprise at least one component selected from the group consisting of bright-field detectors, annular dark-field detectors, high-angle annular dark-field detectors, X-ray detectors, electron energy loss spectrometers, or any combination thereof. In some cases, the detector comprises multiple detectors or detector segments. In some cases, the detector comprises an image sensor. In some cases, the detector comprises a single-channel detector. In some cases, the detector is a multi-channel detector. In some cases, the device is configured to detect in parallel from multiple channels. Further embodiments involving multi-channel detectors are described herein in relation to the “Multiple Detector Segments” section.

[0092] Electron deflector: A deflector 106 may be provided, as shown in Figure 1A. The deflector may be positioned between the electron source and the sample. The systems and methods of this disclosure may also use a fast electrostatic deflector. The fast electrostatic deflector may be installed after the source of the electron beam in a TEM. In some embodiments, when no voltage is applied, the electron beam may pass through normally, and when a voltage is applied, the electrons may be deflected at an angle such that they do not pass through the aperture and do not reach the sample. Thus, the beam may be rapidly turned on and off. In some cases, the beam may propagate through the aperture 108. The voltage applied to the deflector can control whether the electron beam propagates through the aperture or is blocked by the aperture.

[0093] The deflector 106 may modulate the intensity of the electron source directed to the sample area. Modulation may be achieved through one or a combination of the following: pulse width modulation (PWM), pulse density modulation (PDM), or delta modulation (DM). Modulation of the electron source by the deflector may be associated with an electron dose waveform. The provided waveform may modulate the amount of electrons arriving at the sample area (e.g., dose). In some cases, the waveform may determine the time profile of the average dose at the sample area. In some embodiments, a waveform for determining the time profile of the average dose may be provided. The time profile of the average dose may be indicated by the user. The indicated time profile may be converted into a waveform. The conversion to a waveform may be performed or assisted by a processor having instructions such as those disclosed herein. The waveform may be an on-off waveform that varies the average dose over time. The waveform may be amplified to an operating voltage and applied to a fast electrostatic deflector.

[0094] The deflector may comprise one or more electrodes. The deflector may comprise two or more pairs of electrodes. Each pair of electrodes may move electrons in different directions. In some embodiments, various pairs of electrodes may move electrons along different axes. In the embodiment shown, the detector has two electrodes that are shaped like a plate.

[0095] In some cases, the deflector comprises a drive electrode and an electrode at a fixed voltage. In other cases, the deflector comprises a drive electrode near a part of the microscope, which is held at a fixed voltage and acts as a second electrode at the fixed voltage. In some cases, the part of the microscope is a grounded beam tube. In some cases, the magnitude of the drive voltage may range from about 0 volts to about 10 kilovolts (kV). In some cases, the magnitude of the drive voltage may be at least 0 volts, at least 10 volts, at least 100 volts, at least 500 volts, at least 1,000 volts, at least 5 kV, or at least 10 kV. In some cases, the magnitude of the drive voltage may be at most 10 kV, at most 5 kV, at most 1,000 volts, at most 500 volts, at most 100 volts, at most 10 volts, or about 0 volts. In some cases, the drive voltage is in the range of about ±100 to about ±200 volts (V). Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the drive voltage may be in the range of about ±1 to about ±2,000 V, about ±10 to about ±1,000 V, about ±20 to about ±500 V, or about ±50 to about ±500 V.

[0096] In some cases, the deflector comprises two drive electrodes. For example, the two drive electrodes may have opposite voltages. The two drive electrodes may have equal opposite voltages or unequal voltages. In some cases, the magnitude of the drive voltage may range from about 0 volts to about 10 kV. In some cases, the magnitude of the drive voltage may be at least 0 volts, at least 10 volts, at least 100 volts, at least 500 volts, at least 1,000 volts, at least 5 kV, or at least 10 kV. In some cases, the magnitude of the drive voltage may be at most 10 kV, at most 5 kV, at most 1,000 volts, at most 500 volts, at most 100 volts, at most 10 volts, or about 0 volts. In some cases, the drive voltage is in the range of about ±100 to about ±200 volts (V). Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the drive voltage may be in the range of about ±1 to about ±2,000 V, about ±10 to about ±1,000 V, about ±20 to about ±500 V, or about ±50 to about ±500 V.

[0097] Aperture: As shown in Figure 1A, an aperture 108 may be provided. In some cases, multiple apertures may be present. For example, as shown in Figure 1B, apertures may be provided on both sides of the focusing lens and the scanning lens. The first aperture may assist in the collimation of electrons from the electron source. The second aperture may spatially filter the electron beam from the scanning lens. In some cases, the device may also further include an objective lens (OL) that can focus the filtered electron beam before it proceeds to sample S / 110 as herein.

[0098] Analog and Digital Electronic Components: As shown in Figure 1A, the device may comprise a driver electronics unit 120, a digital pattern generator 130, a sequence generation algorithm 140, an event signal processor 150, and a scanning controller 180. For example, the digital pattern generator may produce an electrical signal representing an electron dose waveform. The driver electronics unit may receive the electrical signal from the pattern generator and supply a voltage containing the electron dose waveform to the deflector. The sequence generation algorithm may receive an indication of the electron dose waveform to the user, deliver the indication to the pattern generator, and produce an electrical signal. The event signal processor may process the electron events from the detector and feed the event signals back into the sequence generation algorithm.

[0099] In some cases, the component-driven electronics 120, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 may individually or collectively comprise the controller 160 of the Disclosure. In some cases, signals from the event signal processor may be transmitted to a controller comprising the driver electronics 120 and the digital pattern generator 130. In some cases, the controller may also comprise one or more embodiments of the event signal processor 150 of the Disclosure. In some cases, the controller may comprise one or more processors. In some cases, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 may collectively comprise the electron dose modulator 170 of the Disclosure. In some cases, the controller may comprise one or more field-programmable gate arrays (FPGAs) or one or more ASICs. In some cases, the first field-programmable gate array is configured to control a deflector. For example, the FPGA or ASIC may comprise the driver electronics 120, the digital pattern generator 130, and the sequence generation algorithm 140. In some cases, the drive electronics 120 is substantially analog, and the digital pattern generator 130 and sequence generation algorithm 140 are part of an FPGA or ASIC. In some cases, the event signal processor 150 comprises a second field-programmable gate array. In some cases, the electron dose modulator 170 is implemented on a single FPGA or ASIC. In some cases, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 comprise an FPGA or ASIC, while the drive electronics 120 remains separate. For example, the drive electronics 120 may include a higher voltage switching circuit for the deflector and may be separately shielded from lower voltage components.

[0100] Device 100 may include a scanning controller 180. The scanning controller 180 may include an embodiment of a processor as disclosed herein with respect to the “Computer Systems” section of this specification. In some cases, the scanning controller can control and / or direct commands to one or more components of the electron dose modulator or controller as described herein.

[0101] Quantitative STEM: In some cases, it is conceivable to calibrate the intensity of the scattering signal integrated within each time period (e.g., residence time) of the electron beam over the sample. As a result, when divided by the incident primary beam current, the data has units of "partial scattering." This partial scattering can then be integrated over the area of ​​individual atoms (e.g.) to obtain a scattering cross-section. It is conceivable to determine the scattering rate resulting from this probability by summing all scattering events within the pixel residence time, but there is a possibility of radiation damage occurring when probing these materials.

[0102] Various examples of quantitative STEM methods can be found, for example, in "Experimental Quantification of Annular Dark-Field Images in Scanning Transmission Electron Microscopy" by JM LeBeau and S. Stemmer, Ultramicroscopy 108, 1653 (2008); "Measurement of Composition Profiles in III-Nitrides by Quantitative Scanning Transmission Electron Microscopy" by A. Rosenauer, K. Gries, K. Muller-Caspary, M. Schowalter, A. Pretorius, A. Avramescu, K. Engl, and S. Lutgen, J. Phys. Conf. Ser. 209, 012009 (2010); and "Practical Aspects of Quantitative and High-Fidelity STEM Data Recording" by L. Jones, Scanning Transm. Electron Microsc. 1 The determination of scattering cross sections may be disclosed, for example, in "Probe Integrated Scattering Cross Sections in the Analysis of Atomic Resolution HAADF STEM Images" by H. E, KE MacArthur, TJTJ Pennycook, E. Okunishi, AJJ D'Alfonso, NRR Lugg, LJ Allen, and PD Nellist, Ultramicroscopy 133, 109 (2013) (which is incorporated as a whole by reference).

[0103] Because of the potential for radiation damage, one approach is to reduce the beam current (and therefore the dose intensity) used when performing measurements. In some cases, the beam current can be reduced to an absolute minimum for highly susceptible samples. This results in less data per unit time.

[0104] This disclosure provides an event-driven approach to address two problems: sample damage and increased information acquisition. Determining the scattering event rate may be advantageous. Rather than measuring the rate by dividing the total number of detected events by the total time, the event-driven approach proposed herein may be based on the concept that the time from the start of a pixel to the first event is short for electron beam locations (pixel locations) with high scattering rates, and longer for regions with low scattering rates. Considering that the delay time from the start of a pixel to the first event is the reciprocal of the scattering rate, the scattering rate data may be determined using the timing of the first scattering event.

[0105] In some cases, the delay time t may be counted from the pixel start to the nth event, and the integer n is determined before the pixel start time to provide an estimate of the scattering rate n / t. At least one difference between the event-driven approach and other approaches is that, in some approaches, time t is determined beforehand and the number of counts n is measured, whereas in the event-driven approach, n may be determined beforehand and t may be measured. The event-driven approach can thereby automatically reduce the measurement time when the scattering rate is high. Event signal processor

[0106] Figure 2 illustrates an embodiment of the event signal processor 150 of the present disclosure. As shown, the event signal processor may have one or more inputs and one or more outputs. In some cases, the device includes an event signal processor configured to receive an electronic signal or an electronically induced signal from a detector. The event signal processor may determine the number of electronic events on the detector in response to the detector. The event signal processor may determine the number of events based on the rising edge of the electronic signal or electronically induced signal at the detector.

[0107] In some cases, the event signal processor is part of the controller disclosed herein. In other cases, the event signal processor is separate from the controller. In some cases, the event signal processor has a single event resolution. In some cases, the event signal processor is configured to determine the gradient of an electronic signal or an electronically induced signal. In some cases, an electronic event is correlated with the gradient exceeding a threshold gradient value. In some cases, the event signal processor includes a scintillator or is operably coupled to a scintillator. A scintillation signal may be generated in response to an electronic signal or an electronically induced signal and delivered to the event signal processor as input.

[0108] In some cases, the event signal processor includes an output signal. The output signal from the event signal processor may be fed as a signal into an electron dose modulator to determine a continuously variable time profile. The output signal may include an instantaneous trigger signal. In some cases, the event signal processor may be configured to compare an electron signal or electron-induced signal with a set of logic conditions. In some cases, the comparison of the electron signal or electron-induced signal with the set of logic conditions can generate an output signal.

[0109] The output signal may be a trigger signal. The trigger signal may be instantaneous. The trigger signal may be induced with a delay for a pixel dwell time of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, or less than 1,000 nanoseconds. The trigger signal may be induced with a delay that is less than the pixel dwell time.

[0110] A set of logical conditions may be at least partially based on one or a combination of event conditions. Event conditions may include one or more threshold event counts, one or more threshold event rates, absence of events after a certain time period, one or more event measurements, a mutual information threshold, or a combination thereof. Event conditions may be event conditions in one or more detectors, or in one or more subregions of one or more detectors. Event conditions may comprise measurements in multiple detectors or regions of detectors. Event conditions may comprise multiple threshold event conditions, where each measurement in multiple detectors or regions of detectors comprises a threshold condition to which multiple threshold conditions are associated. Event conditions may vary depending on the sample location.

[0111] A set of logical conditions may be user-defined. In some cases, logical conditions may be described by condition codes. A condition code may consist of a set of logical conditions, a reference to a lookup table describing a set of logical conditions, or a combination thereof.

[0112] Figure 3A illustrates exemplary single-electron collision event traces according to several embodiments. As shown in panel 310, the electron signals are correlated with rising and falling edges. When several electron collisions occur in temporal proximity to each other, for example at 22 microseconds in Figure 3A, the signals from each electron may obscure each other. As shown in panel 320, signal gradients may be provided. For example, the gradients may be generated in hardware or calculated numerically (e.g., by software). Signal gradients can effectively sharpen the electron signals and improve effective time resolution. As shown in panel 320, overlapping electron signals at similar event times may be separable. For example, at 22 microseconds, three events appear as three distinct electron signals.

[0113] Figures 3B-3D show the analog signal, the signal from the event process, and the signal (intensity) on a line of pixels (vertical) as a function of time (horizontal) for each combination of the two. Figure 3B shows only the analog processor. As shown, the signal in time appears as stripes. Figure 3C shows the signal (pulse) from the event signal processor. As shown, the event appears as a point. Figure 3D shows the signals from both methods, combined to highlight the changes in the time profile. Thus, a high-speed electronic event processor may enable improved single-electron counting.

[0114] Additional details relating to the event signal processor of this disclosure may be provided in at least T. Mullarkey, C. Downing, and L. Jones, “Development of a Practicable Digital Pulse Read-Out for Dark-Field STEM,” Microsc. Microanal. 27, 99 (2021) and JJP Peters, T. Mullarkey, and L. Jones, “Improving the Noise Floor and Speed ​​of Your Detector: A Modular Hardware Approach for Under $1000,” Microsc. Microanal. 28, 2904 (2022) (each of which is incorporated herein by reference as a whole). Electron dose modulator

[0115] The systems and methods of this disclosure may also provide an electrostatic dose modulator (EDM) driven by an arbitrary trigger signal.

[0116] Figure 4 illustrates an embodiment using variable blanking enabled by an electrostatic dose modulator driven by an arbitrary trigger signal. The electron dose modulator may comprise a driver electronic device 120, a digital pattern generator 130, and a sequence generation algorithm 140. In some cases, a signal from an event signal processor may be transmitted to a controller comprising the driver electronic device 120 and the digital pattern generator 130. In some cases, the controller may also comprise one or more embodiments of the event signal processor 150 of the present disclosure. In some cases, the modulation step includes the use of a deflector. For example, the digital pattern generator may control a deflector that switches the electron source according to the pattern of the pattern generator. The pattern generator may be a low-voltage signal that can be transmitted to the driver electronic device. In some cases, the modulation step includes moving the electron source to a different location on the sample. In some cases, the modulation step includes turning off the electron source.

[0117] The device may include a drive electronic device 120. The drive electronic device receives an electrical signal from a digital pattern generator, outputs a voltage, and drives the electrodes of the deflector. The drive electronic device may include a digital power amplifier. The digital power amplifier may mirror the incoming digital pattern on the deflector plate. The drive electronic device can facilitate waveform flexibility in the PWM modulation scheme. The drive electronic device may include analog signal conditioning components, such as a low-pass filter, a high-pass filter, a DC offset, ground, shielding, etc. The drive electronic device may include a separate channel for driving the electrodes.

[0118] The drive electronics may provide fast transition times. In some cases, the transition between high and low deflector voltages may be characterized by the transition time. For example, the transition time between high and low voltages is less than about 50 nanoseconds, defined as the sum of ringing time and slope time. The drive electronics may provide sustained high frequencies. For example, the frequencies provided by the drive electronics may be in the range of about 500 kHz (kilohertz) to about 1 MHz (megahertz) at electron beam voltages in the range of about 80 kV to about 300 kV.

[0119] The device may include a pattern generator 130. The pattern generator may be an analog or digital pattern generator. The digital pattern generator may take waveform indications from an algorithm and produce an electrical signal representing an electron dose waveform. The signal representing the electron dose waveform may be a lower voltage signal than that provided to the deflector by the drive electronics. The digital pattern generator may receive various parameters related to the shape of the waveform. The parameters may together include waveform indications. The various parameters may include indications of any of the waveform properties disclosed herein. The digital pattern generator may receive synchronization signals from other parts of the microscope, such as those disclosed herein. The pattern generator may be programmable. The pattern generator may be integrated with other sensors and workflows in the microscope, such as those described herein with respect to sequence generation algorithms. The digital pattern generator may include a pulse width modulator. The digital pattern generator may generate DM, PWM, and / or PDM modulation schemes. The digital pattern generator may include a digital-to-analog (DAC) converter or an analog-to-digital (ADC) converter. In some cases, the digital pattern generator includes a DAC and / or ADC to control one or more components of the microscope, for example, to synchronize them with the dose waveform.

[0120] A pattern generator may also be a function generator. A function waveform generator may generate a waveform having a profile determined by a regular periodic function. The regular periodic function may include pulse patterns or regular pulse patterns, such as a square wave, a sine wave, or a regularly repeating pulse, and the non-periodic function may include a ramp pulse, a Gaussian, a Laurentian, an exponential rise, an exponential decay, and a semi-arrow function. The waveform may be an electron or ion dose waveform.

[0121] The pattern generator may be an arbitrary pattern generator. The arbitrary pattern generator may generate a waveform having a profile not determined by a regular periodic function. The waveform may be an arbitrarily defined waveform. The arbitrarily defined waveform may not have a regular pulse width, or a regular repetition rate, or neither. The arbitrarily defined waveform may have a selectable irregular pulse width, or a selectable irregular repetition rate, or both. The waveform may be an electron or ion dose waveform.

[0122] The device may include a sequence generation algorithm 140. The sequence generation algorithm may be an algorithm that can take into account one or more of the following to form the electron dose waveform indication of the Disclosure: information about the sample, deflection electronics, detectors involved in the measurement, and determined waveforms input to the control software by the user.

[0123] In some cases, the electron dose waveform may modulate the average intensity of the electron source directed toward the sample area. In other cases, the average intensity may be modulated substantially without changing other imaging conditions. For example, the time profile of the waveform may be set, and instrument matching may be set, but it may be desirable to change the average intensity of the electron dose. In some cases, the average intensity can be controlled independently of the driving voltage of the electron source.

[0124] Examples of electron dose modulators that may be used in conjunction with this disclosure are provided, but are not limited to, U.S. Patent No. 11,476,082 and “Electrostatic Switching for Spatiotemporal Dose Control in a Transmission Electron Microscope” by BW Reed, RS Bloom, G. Eyzaguirre, C. Henrichs, AA Moghadam, and DJ Masiel, Microsc. Microanal. 28, 2230 (2022) (each of which is incorporated herein by reference as a whole).

[0125] Referring again to Figure 4, the figure shows three embodiments of signals that may be delivered from the scanning controller 180 to the electron dose modulator 170 of the present disclosure. The signals may relate to the electronic signals or electron-induced signals of the present disclosure.

[0126] In some cases, the signal from the scanning controller 180 may include a trace 410. The trace 410 indicates a vertical synchronization signal that can be directed to the driver electronics 120 of the Disclosure through the electron dose modulator 170. The vertical synchronization signal may control the first axis of the deflector of the Disclosure. The trace 410 indicates a square pulse associated with one or more electronic signals or electron-induced signals. In the trace 410, a frame may be recorded after a square pulse, and a frame may not be recorded after a second square pulse.

[0127] In some cases, the signal from the scanning controller 180 may include a trace 420. The trace 420 indicates a horizontal synchronization signal that can be directed to the driver electronics 120 of the Disclosure through the electron dose modulator 170. The horizontal synchronization signal may control a second axis of the deflector of the Disclosure. The trace 420 indicates a series of square pulses associated with one or more electronic signals or electron-induced signals. The trace 420 may include an on / off signal.

[0128] In some cases, the signal from the scanning controller 180 may include a trace 430. The trace 430 represents a pixel clock signal, which can be directed to the driver electronics 120 of the Disclosure through the electron dose modulator 170. The pixel clock signal may be directed to the electron dose modulator to form the arbitrary electron dose waveform of the Disclosure. The trace 430 represents a series of delta pulses associated with one or more electron signals or electron-induced signals. In some cases, the trace 430 may be associated with a single electron count on one or more detectors or one or more portions of detectors.

[0129] In some cases, the digital pattern generator may receive a signal from the scanning controller. The signal may include a pixel clock signal 430. In some cases, the digital pattern generator may also receive a horizontal synchronization signal (410) and a vertical synchronization signal (420). These signals can provide the digital pattern generator with information about the location of the beam in the raster sequence, for example, where the beam is pointed over the sample. In one embodiment, if the digital pattern generator receives the nth electronic count from the event signal processor within a single pixel residence time, the digital pattern generator may provide a signal to the driver electronics to blank the beam until the next pixel clock, at which point this may reset the count to zero and repeat.

[0130] In some cases, the threshold may be a combination of total count and count rate, which may vary as a function of position across the sample. A digital pattern generator may receive a timing signal and have enough information to understand where the beam is impacting the sample. Using information from previous (e.g., lower dose) scans of the same area, the user (or an algorithm such as a machine learning algorithm) may distinguish different areas of the sample that should receive higher or lower doses depending on their tendency to be damaged by the electron beam.

[0131] In some cases, the digital pattern generator may transmit a subset of signals 410, 420, and 430 to driver electronics that control the scanning coil. The digital pattern generator may, for example, when the event signal processor has not received any signals, emit uniformly spaced pixel clocks for a predetermined maximum pixel dwell time. In another embodiment, if a threshold is reached before the end of this dwell time, the next pixel clock signal may be transmitted early, and the scan may jump to the next pixel. This would have the effect of both reducing dose and increasing acquisition speed.

[0132] Signals 410, 420, and 430, either individually or in any combination, may be directed to the digital pattern generator of the Disclosure. The electron dose modulator may comprise a portion of the electron dose modulator. The electron dose modulator may comprise a field-programmable gate array. The electron dose modulator may form an electron dose waveform based on an electron signal or an electron-induced signal. Signal 440 represents an exemplary electron dose waveform of the Disclosure, which may be directed to a deflector via driver electronics. In some cases, each pixel or each detector or portion of a detector may receive its own electron dose waveform. In some cases, each pixel or each detector or portion of a detector may receive different pre-programmed pulse durations. In some cases, each pixel or each detector or portion of a detector may receive an on / off signal, a signal with a continuously variable time profile, or an arbitrary electron dose waveform that determines when it records a signal or not.

[0133] In some cases, the controller of the present disclosure comprises a pattern generator configured to produce an electrical signal representing an electron dose waveform, and driver electronics configured to receive the electrical signal from the pattern generator and supply a voltage comprising the electron dose waveform to a deflector. In some cases, the controller further comprises one or more computer processors configured, when executed, to receive an indication of an electron dose waveform and deliver the indication to the pattern generator. In some cases, the controller of the present disclosure is configured to determine the time to keep the electron signal on in response to an electron event signal.

[0134] In some cases, each pixel or each detector or each part of a detector may receive an on / off signal, a signal with a continuously variable time profile, or an arbitrary electron dose waveform that determines whether or not to record the signal. In some cases, the continuously variable time profile is modulated in "real time." In some cases, "real time" substantially includes within the electron counting interval of the detector.

[0135] The electron dose waveform may have an arbitrarily defined time profile. The arbitrarily defined electron dose profile may not be determined by a regular periodic function. The regular periodic function may include pulse patterns or regular pulse patterns, e.g., square waves, sine waves, or regularly repeating pulses, and the non-periodic function may include ramp pulses, Gaussian, Laurentian, exponential rise, exponential decay, and semi-arrow functions. The arbitrarily defined electron dose waveform may not have a regular pulse width, or a regular repetition rate, or neither. The arbitrarily defined electron dose waveform may have a selectable irregular pulse width, or a selectable irregular repetition rate, or both.

[0136] In some cases, an arbitrarily defined electron dose profile may comprise a dose profile with a series of points (e.g., intermediate points). The waveform may be interpolated from the series of points. The series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some cases, the arbitrarily defined time profile is provided by the user. In some cases, the user may provide a function that generates a series of intermediate points. In some cases, the user may move intermediate points or sets of intermediate points individually to change the waveform. In some cases, the electron dose waveform is aperiodic.

[0137] In some cases, the time profile has time resolution. In other cases, time resolution is defined as the distance between intermediate points in an arbitrarily defined time profile. The time resolution may be less than about 100 nanoseconds (ns). The time resolution may be less than about 50 nanoseconds. The time resolution may be less than about 10 nanoseconds (ns). The time resolution may be, at will, less than about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, about 1 nanosecond, about 500 picoseconds (picoseconds), about 250 picoseconds, about 100 picoseconds, about 50 picoseconds, about 20 picoseconds, about 10 picoseconds, about 5 picoseconds, about 1 picosecond, about 500 microseconds (microseconds), about 250 microseconds, about 100 microseconds, about 50 microseconds, about 20 microseconds, about 10 microseconds, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the time resolution may be in the range of about 100 nanoseconds to about 5 nanoseconds, about 50 nanoseconds to about 1 nanosecond, or about 20 nanoseconds to about 1 nanosecond.

[0138] In some cases, a series of intermediate points comprises more than approximately 1,000 intermediate points. In some cases, a series of intermediate points comprises more than approximately 10,000 intermediate points. In some cases, a series of intermediate points comprises more than approximately 100,000 intermediate points. In some cases, a series of intermediate points comprises more than approximately 1,000,000 intermediate points. In some cases, a series of intermediate points comprises between approximately 10,000 and approximately 1,000,000 intermediate points. In some cases, a series of intermediate points is repeated several times to form a sequence. In some cases, a sequence is repeated approximately 10 times, approximately 100 times, approximately 1,000 times, approximately 10,000 times, approximately 100,000 times, approximately 1,000,000 times, or more. Any of the lower and upper limits described in this paragraph may be combined to form a range included within this disclosure, for example, the number of repetitions in a time series may be in the range of about 10 to about 10,000, about 1 to about 100, or about 1 to about 1,000.

[0139] In some cases, a waveform may comprise multiple pulses within a sequence. For example, an electron dose waveform may comprise a pump pulse and a probe pulse. A pump-probe experiment may be used to measure a time-dependent process in a sample. In some cases, the pump pulse and probe pulse may have the same shape, e.g., two Gaussians, two Laurentian, two square waves, etc. In some cases, the shapes of the two pulses may be different, e.g., exponential decay and Gaussian or any two other pulse types described herein. A series of pulses may be repeated several times to form a sequence. In some cases, the sequence may be repeated about 10, about 100, about 1,000, about 10,000, about 100,000, about 1,000,000, or more. Any of the lower and upper limits described in this paragraph may be combined to form a range included within this disclosure, for example, the number of repetitions in a time series may be in the range of about 10 to about 10,000, about 1 to about 100, or about 1 to about 1,000.

[0140] In some cases, the repetition rate of a series of electron dose waveforms is above approximately 1 kHz, approximately 5 kHz, approximately 10 kHz, approximately 20 kHz, approximately 50 kHz, approximately 100 kHz, or higher. In other cases, the repetition rate of a series of electron dose waveforms is below approximately 1,000 MHz, approximately 500 MHz, approximately 200 MHz, approximately 100 MHz, or lower. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the repetition rate of a series of electron dose waveforms may be approximately 500 kHz to approximately 1 MHz, approximately 100 kHz to approximately 10 MHz, or approximately 10 kHz to approximately 100 MHz.

[0141] In some cases, the minimum repetition period of a series of electron dose waveforms may be, at will, about 100 milliseconds, about 50 milliseconds, about 20 milliseconds, about 10 milliseconds, about 5 milliseconds, about 1 microsecond, about 500 microseconds, about 250 microseconds, about 100 microseconds, about 50 microseconds, about 20 microseconds, about 10 microseconds, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the minimum repetition period may be in the range of about 1 millisecond to about 1 microsecond, about 100 microseconds to about 1 microsecond, or about 20 nanoseconds to about 1 microsecond.

[0142] The electron dose waveform may have a continuously variable time profile. For example, the user may determine the waveform and later modify it. Modifications may include changing the location of one or more intermediate points, changing the time between repetitions of a series of waveforms, changing the number of repetitions, etc. In some cases, the pulse width of the square wave may be dynamically changed. For example, the pulse width of a series of square waves may be aperiodic or have a continuously adjustable periodicity.

[0143] In some embodiments, the user may choose between an arbitrarily defined time profile and a regular periodic function. For example, the deflector may provide a pulse pattern or a regular pulse pattern, such as a square wave, sinusoidal wave, or TTL pulse, and may include regularly repeating pulses, ramp pulses, Gaussian, Laurentian, exponential rise, exponential decay, and semi-arrow functions to the deflector. In some cases, the electron dose waveform is periodic.

[0144] In some cases, the transition between high and low deflector voltages may be characterized by the transition time. For example, the transition time between high and low voltages is less than about 50 nanoseconds, defined as the sum of ringing time and slope time. In other cases, the transition time between high and low voltages is less than about 1 microsecond, about 500 nanoseconds, about 250 nanoseconds, about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, or less than that.

[0145] In some cases, the transition between high and low deflector voltages may be characterized by the transition time. For example, the transition time between high and low voltages is less than about 10 nanoseconds, defined as the slope time of the transition voltage from about 10% to about 90%. In other cases, the transition time between high and low voltages is less than about 1 microsecond, about 500 nanoseconds, about 250 nanoseconds, about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, about 2 nanoseconds, about 1 nanosecond, or less than that.

[0146] In some cases, the electron dose waveform is characterized by the shortest exposure time. For example, the electron dose waveform may have a shortest exposure time of about 100 nanoseconds. In other cases, the shortest exposure time is about 1 microsecond, about 500 nanoseconds, about 250 nanoseconds, about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, about 2 nanoseconds, about 1 nanosecond, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the shortest exposure time may be in the range of about 500 nanoseconds to about 1 nanosecond, about 100 nanoseconds to about 5 nanoseconds, about 50 nanoseconds to about 1 nanosecond, or about 20 nanoseconds to about 1 nanosecond.

[0147] In some cases, the time profile includes a pulse width. The minimum pulse width may be less than about 100 nanoseconds (ns). The minimum pulse width may be less than about 50 nanoseconds. The time resolution may be less than about 10 nanoseconds. The minimum pulse width may optionally be less than about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, about 1 nanosecond, about 500 picoseconds (picoseconds), about 250 picoseconds, about 100 picoseconds, about 50 picoseconds, about 20 picoseconds, about 10 picoseconds, or less than these. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the minimum pulse width may be in the range of about 100 nanoseconds to about 5 nanoseconds, about 50 nanoseconds to about 1 nanosecond, or about 20 nanoseconds to about 1 nanosecond.

[0148] In some cases, the time profile includes the fastest pulse duration. The fastest pulse duration may be less than about 200 nanoseconds (ns). The fastest pulse duration may be less than about 100 nanoseconds. The time resolution may be less than about 50 nanoseconds. The fastest pulse duration may optionally be less than about 100 nanoseconds, about 50 nanoseconds, about 20 nanoseconds, about 10 nanoseconds, about 5 nanoseconds, about 1 nanosecond, about 500 picoseconds (picoseconds), about 250 picoseconds, about 100 picoseconds, about 50 picoseconds, about 20 picoseconds, about 10 picoseconds, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the fastest pulse duration may be in the range of about 100 nanoseconds to about 5 nanoseconds, about 50 nanoseconds to about 1 nanosecond, or about 20 nanoseconds to about 1 nanosecond.

[0149] In some embodiments, dose modulation may be implemented using a fast electrostatic shutter. The electron beam may be rapidly blanked at a fixed repetition rate (kHz to MHz) so that the average dose is reduced. In this embodiment, the peak dose rate cannot change. If the average dose rate or repetition frequency is changed, the setting may become effective after a delay. In some cases, the delay may be a non-repeatable delay, a regularly repeatable delay, or an irregularly repeating delay.

[0150] The repetition rate of the electron dose waveform in shutter mode may be in the range of approximately 500 kHz to approximately 1 MHz for electron beam voltages in the range of approximately 80 kV to approximately 300 kV. The repetition rate may be in the range of approximately 10 kHz to approximately 100 MHz for electron beam voltages in the range of approximately 80 kV to approximately 300 kV. The repetition rate may be in the range of approximately 500 kHz to approximately 1 MHz for electron beam voltages in the range of approximately 0.5 kV to approximately 1,000 kV.

[0151] In some cases, the repetition rate of the electron dose waveform is above approximately 1 kHz, approximately 5 kHz, approximately 10 kHz, approximately 20 kHz, approximately 50 kHz, approximately 100 kHz, or higher. In other cases, the repetition rate of the electron dose waveform is below approximately 1,000 MHz, approximately 500 MHz, approximately 200 MHz, approximately 100 MHz, or lower. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, approximately 500 kHz to approximately 1 MHz, approximately 100 kHz to approximately 10 MHz, or approximately 10 kHz to approximately 100 MHz.

[0152] A variable adjuster, such as a knob, lever, slider, or dial, may be connected to the digital pattern generator. The variable adjuster may be a physical or virtual knob for adjusting the average intensity. In some cases, the average intensity can be controlled independently of the electron source drive voltage. For example, the average intensity may involve adjusting the time delay between electron pulses, narrowing the duration of electron pulses, or directly adjusting the amplitude of the waveform.

[0153] In some cases, the average intensity is continuously variable over a range of 0–100% dose transmission or 0–100% dose decay. Dose decay (also called decay rate) may be expressed as a ratio a / b, where a is the pulse width and b is the period of the electron dose waveform. Dose decay may also be expressed as a percentage. Dose transmission may be related to dose decay by the relationship, i.e., dose transmission = 100% - percentage.

[0154] In some cases, the average intensity is continuously variable over the range of 0–100% dose transmission or 0–100% dose decay in increments of approximately 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, 0.01%, 0.001%, or less.

[0155] Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, dose decay may vary in increments within ranges such as about 30% to about 0.01%, about 10% to about 0.1%, about 30% to about 1%, and about 10% to about 0.01%.

[0156] The ratio of pulse width to period (a / b) may vary over time. For example, it may vary over a period of 20 seconds. The ratio may vary over a period of time of about 100 seconds, about 50 seconds, about 20 seconds, about 10 seconds, about 5 seconds, about 1 second, about 500 milliseconds, about 250 milliseconds, about 100 milliseconds, about 50 milliseconds, about 20 milliseconds, about 10 milliseconds, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form a range included in this disclosure, for example, the ratio may vary over a period of time of about 100 seconds to about 1 millisecond, about 100 seconds to about 1 second, or about 50 seconds to about 1 second, etc.

[0157] The combination of an event signal processor and a digital pattern generator may enable the device to detect one (or more) electronic events and then switch the electron beam with very precise control (on the order of 10 nanoseconds). Once enough events have been captured to determine the scattering rate at a given pixel, the beam can be blanked for the remainder of the time. This may occur after one event or after several more events. Information efficiency

[0158] As disclosed herein, diminishing returns to information content may exist for each additional electron that successively collides with the sample within a single pixel or portion of the detector. To illustrate this principle, a simple Bayesian model was constructed using a system that counts the electron detection probability p (ranging from 0 to 1) and the arrival time t of the nth electron reaching the detector. For convenience, time t is expressed with respect to the electron beam current such that, on average, one electron arrives per unit of time. For the purposes of this embodiment, it is assumed that the value of p is maximally unknown before measurement (in this embodiment, uniformly distributed between 0 and 1, which is the prior probability distribution). The amount that can be learned about the value of p by measuring the arrival time t was investigated. This statistical distribution of arrival times was computed using the mathematical theory of Poisson processes and, according to Bayes' theorem, can yield a likelihood function that determines the posterior distribution of p after measurement.

[0159] Figure 5 shows a representation of cumulative and incremental mutual information for consecutive electron detection events. The information obtained about the value of p may be quantified using an information-theoretic concept called "mutual information," which can be expressed in bits. Mutual information is a measure of the quantity learned on average about a sample by making measurements. Mutual information is calculated as the difference between the prior differential entropy and the expected posterior differential entropy with respect to the probability distribution over the variable p. This model yields the graph shown in Figure 5.

[0160] As shown, on the left side of the graph, when 0 electrons are detected (for example, before measurement is performed), the mutual information is 0, and nothing is learned about the material. The arrival time of the first electron yields approximately 0.43 bits of information on average. If it arrives in a short amount of time, it suggests that p is probably large, and conversely, if it takes a long time to arrive, it suggests that p is probably small. This intuition is quantitatively represented by the posterior probability distribution of p. The more electrons counted, the more information is obtained, allowing the value of p to be determined with increasing accuracy. This is shown at the "cumulative" (circle) points on the graph. Thus, after measuring two electrons, on average, a total of 0.67 bits of information are learned about the sample, after measuring three electrons, 0.84 bits are learned, and so on. This curve exhibits approximately logarithmic diminishing returns (smooth curve on the graph). Each electron provides more information than before, but the increment is steadily diminishing (point X on the graph). Therefore, the second electron provides 0.67 - 0.43 = 0.24 bits of information that were not yet obtained from the detection of the first electron, the third electron provides an additional 0.17 bits, and so on. This diminishing returns of information is common across a wide range of similar models. Assuming prior knowledge about p, for example, the curve shifts in both x and y, but the fundamental behavior remains unchanged.

[0161] This logarithmic dependence means that the first electron brings about approximately the same amount of information as the second and third electrons it combines with, or electrons 4-7, or subsequent electrons 8, etc. In contrast, the probability of beam-induced sample damage is at least constant for each incident electron, and potentially increases further with cumulative dose if multi-excitation events or thermal accumulation occur. Therefore, as the electron source continues to collide with the same pixel using electrons, the experimenter potentially learns less and less incrementally, while increasingly damaging the sample. Information-efficient electron detection

[0162] This disclosure provides methods and systems for information-efficient electron detection. For example, this disclosure provides a method for measuring an electron signal or an electron-induced signal. In one embodiment, a maximum number n of electrons to be counted within a single residence time can be set, and then the beam can be blanked. The arrival time of the number of electrons n (or, if fewer than n arrive during the residence time, the number of electrons detected) then allows for the estimation of the most likely value of p for that pixel. The parameter n may be selected based on the amount of information per pixel required for a specific application. Once information up to a threshold has been acquired, irradiation of the sample can be stopped, allowed to cool for a period of time to allow the charge to dissipate or relax in some way, and then the process can be repeated by proceeding differently to the next pixel position. Combining the electron dose modulator of this disclosure with an electron event counter may be advantageous when carrying out the methods described herein.

[0163] While not limited by theory, the achievable relative irradiation savings may depend on several further factors, including residence time, sample scattering rate (e.g., mass thickness in the case of ADFs, although different mechanisms are associated with different types of detectors), detector collection efficiency, event detection timing accuracy, inter-pixel variation in scattering rate, and beam blanker response speed.

[0164] Figure 6 shows an exemplary method 600 of the present disclosure. Method 600 may include embodiments of a method for measuring an electronic signal or an electronically induced signal.

[0165] Operation 610 of Method 600 may include a step of providing a threshold event count or threshold event rate for a pixel on the detector. In some cases, the threshold event count may be the number of events at a single pixel. In some cases, the threshold event count may be the average or sum of events at many pixels. In some cases, the event may be an electron collision. In some cases, the event may be a single count at the electron detector. In some cases, the signal at the detector may be an electron signal or electron-induced signal from a sample. In some cases, the step of determining whether a count has been achieved may be determined using an event signal processor such as those disclosed herein with respect to the "Event Signal Processor" section.

[0166] The threshold may be determined by various techniques. For example, the threshold may be based on a damage threshold for a sample. The threshold may be determined based on the information gain for pixels below a threshold. The threshold may be determined experimentally. The threshold may be set by the user. The threshold may be varied by the user. The threshold may be set using input from an information efficiency model. In some cases, the threshold number of events or threshold event rate is determined based on information about the sample. Further descriptions of thresholding techniques, any of which may be used in combination with Method 600, are disclosed herein in relation to the sections “Complex Thresholding” or “Algorithmic Thresholding”.

[0167] Operation 620 of Method 600 may include the step of collecting a threshold number of events from a detector or the step of determining whether a threshold event rate has been achieved. The collecting step may include the use of a detector of the Disclosure, for example, detector 104. In some cases, a signal from an event signal processor may be delivered to a controller of the Disclosure. The controller may take the event count signal and determine whether a threshold has been achieved.

[0168] In operation 630 of method 600, the method may include a step of modulating the intensity of an electron source directed to the sample in response to the acquisition step in 620. In some cases, a signal from the event signal processor may be transmitted to a controller comprising driver electronics 120 and a digital pattern generator 130. In some cases, operation 630 includes the use of a deflector. For example, the digital pattern generator may control a deflector that switches the electron source according to a pattern of the pattern generator. The pattern generator may be a low-voltage signal that can be transmitted to the driver electronics. In some cases, operation 630 includes a step of moving the electron source to a different location on the sample. In some cases, operation 630 includes a step of turning off the electron source.

[0169] Driver electronics may take a low-voltage signal and convert it to a high-voltage signal, which may be used to apply the high voltage to a plate and deflect the electron beam. The sequence generator 140 of this disclosure may include a set of circuits or digital instructions on a controller for determining the waveform of the signal to be generated in the pattern generator. As disclosed herein, the waveform may be an arbitrary electron dose waveform. In some cases, operation 630 is performed substantially in real time. For example, real time may include a time substantially within the electron counting interval of the detector. Real time may refer to a response time of about 1 microsecond, 1 / 10th of a microsecond, 1 / 100th of a microsecond, 1 nanosecond, 1 / 10th of a nanosecond, 1 / 100th of a nanosecond, 1 picosecond, or less than that.

[0170] In some cases, operation 630 includes a step of modulating the electron dose waveform, which is continuously updated based on the number of events determined from the signal. The electron dose waveform may have a continuously time-variable profile. In some cases, the electron dose waveform has an arbitrarily defined time profile. For example, the arbitrarily defined time profile may have a time resolution of less than 10 nanoseconds.

[0171] In some cases, the electron dose waveform comprises a series of intermediate points. In some cases, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some cases, the sequence comprises more than 1,000 intermediate points. In some cases, method 600 further includes the step of receiving an indication of an arbitrarily defined time profile from a user.

[0172] For illustrative purposes, the methods of this disclosure are compared to compressed sensing (CS). Examples of CS methods are presented in "Implementing an Accurate and Rapid Sparse Sampling Approach for Low-Dose Atomic Resolution STEM Imaging" by L. Kovarik, A. Stevens, A. Liyu, and ND Browning, Appl. Phys. Lett. 109, 164102 (2016) and "Applying Compressive Sensing to TEM Video: A Substantial Frame Rate Increase on Any Camera" by A. Stevens, L. Kovarik, P. Abellan, X. Yuan, L. Carin, and ND Browning, Adv. Struct. Chem. Imaging 1, 10 (2015) (each of which is incorporated as a whole by reference).

[0173] In short, compressed sensing can be an undersampling / inpainting approach. In this form of CS, the beam is scanned in a sparse manner, meaning that a certain percentage of pixels are illuminated. This percentage can be as low as 10% or even lower, but a significant amount of electron dose is used within each pixel. This may have some minor advantages if analog Gaussian readout noise is dominant in the system (e.g., from low-quality electronics) or if the primary goal is video frame rate, not accuracy. See, for example, Sanders, et al., "Inpainting vs denoising for dose reduction in scanning-beam microscopies," IEEE Transactions on Image Processing, Vol. 29, pp. 351-359 (2020) (integrated as a whole by reference).

[0174] However, Gaussian readout noise can be substantially reduced by using a digital STEM detector readout approach. Therefore, compressed sensing cannot yield any further information content. Furthermore, based on the diminishing returns of information discussed above, CS may, in some cases, even be less efficient than non-CS scanning with the same total dose in terms of information returns per electron.

[0175] The methods and systems disclosed herein can improve dose reduction approaches in CS because, in these methods, timing data can be utilized to determine the scattering rate early in the pixel residence time, and the beam can be stopped for the remainder of the duty cycle. In contrast, in CS, a certain percentage of pixels, in some cases as low as 10%, may be illuminated, while no information is obtained at all from unilluminated pixels. The methods and systems disclosed herein can improve existing methods because the dose can be adjusted to all pixels to optimize information efficiency. The methods and systems disclosed herein can improve existing methods because the frame rate can be increased, at least when a trigger signal is used to skip ahead to the next pixel when sufficient counts have been collected. The methods and systems disclosed herein can improve existing methods because, at least, the image can be rendered live (without waiting for the complete image raster to be completed), which CS is not capable of doing. Compared to CS, this disclosure is compatible with row-based non-rigid alignment (e.g., SmartAlign) as described, for example, in "Smart Align—a New Tool for Robust Non-Rigid Registration of Scanning Microscope Data" by L. Jones, H. Yang, TJ Pennycook, MSJ Marshall, S. Van Aert, ND Browning, MR Castell, and PD Nellist, Adv. Struct. Chem. Imaging 1, 8 (2015) (which is incorporated herein by reference for any purpose). Compared to CS, this disclosure is robust against artifacts.Compared to CS, this disclosure is compatible with line interlacing or line flyback hysteresis compensation, such as described, for example, in "Using Your Beam Efficiently: Reducing Electron Dose in the STEM via Flyback Compensation" by T. Mullarkey, J.JP Peters, C. Downing, and L. Jones, Microsc. Microanal. 28, 1428 (2022) (which is incorporated herein by reference as a whole). Compared to CS, this disclosure is compatible with STEM moiré imaging, such as described, for example, in "Quantitative Measurement of Strain Field in Strained-Channel-Transistor Arrays by Scanning Moiré Fringe Imaging" by S. Kim, Y. Kondo, K. Lee, G. Byun, J. Jung Kim, S. Lee, and K. Lee, Appl. Phys. Lett. 103, 033523 (2013) (which is incorporated herein by reference as a whole). In comparison to CS, this disclosure is compatible with fully spatially sampled event-based EELS, such as those disclosed in, for example, Y. Auad, M. Walls, J.-D. Blazit, O. Stephan, HG Tizei, M. Kociak, F. De La Pena, and M. Tence's "Event-Based Hyperspectral EELS: Towards Nanosecond Temporal Resolution" (undated) (which is incorporated herein by reference as a whole).

[0176] Drift Correction and Non-Rigid Alignment – ​​Drift correction and non-rigid alignment can be used in high-resolution STEM imaging applications. However, these techniques generally rely on a simple one-to-one correspondence between pixel coordinates and pixel time. The algorithms generally assume that the image is densely sampled with information at every pixel. However, strategies that implement compressed sensing (either by pixel jumping or row hopping) break this relationship, as most pixels in the image are never sampled. This means that many high-performance alignment algorithms are not available. Missing pixels can be inpainted based on probabilistic models and neighbor information, but this is time-consuming and may lack fully resolved spatial information in densely sampled images. The devices and methods disclosed herein may be capable of reserving Shannon scanning rasters, for example, to facilitate affine transformations of the data.

[0177] Complex Thresholding—An exemplary approach to determining blanking thresholds may involve designating signals in one detector or segment as "drivers" and others as "driven." The driver channel may be used for event counts used to trigger beam blanking, and one or more additional channels (e.g., one or both of the driving and non-driving) may be logged for electronic events up to this point. In some cases, the detection channel used for the driving segment may be the one expected to have the weakest scattering rate. The segment with the lowest scattering rate may be the highest angle of any arranged dark-field ring, or the smallest of any segmented area. Selecting the channel with the lowest scattering collection efficiency may then be expected to receive the fewest electronic events, although due to the statistical nature of electron scattering, other channels may receive more or fewer events during the pixel beam-on duration.

[0178] In some cases, the same channel may be used to drive the entire image frame (field of view), but in other cases, the driving channel may be used at different times during acquisition. For example, in the case of geometrically equivalent detectors such as four-quadrant differential phase contrast (DPC) geometry, four quadrants of equal size are commonly used to detect the DPC signal, and in this case, any of these four that first reaches the event threshold may be the driving channel.

[0179] Exemplary DPC geometry methods are described, for example, by K. Muller, FF Krause, A. Beche, M. Schowalter, V. Galioit, S. Loffler, J. Verbeeck, J. Zweck, P. Schattschneider, A. Rosenauer, K. Muller-Caspary, FF Krause, A. Beche, M. Schowalter, V. Galioit, S. Loffler, J. Verbeeck, J. Zweck, P. Schattschneider, and A. Rosenauer, “Atomic Electric Fields Revealed by a Quantum Mechanical Approach to Electron Picodiffraction,” Nat. Commun. 5, 1 (2014) and N.H. Dekkers and H. de Lang, “Differential Phase Contrast in a STEM,” Optik (Stuttg). 41, 452 Disclosed in (1974) (each of which is incorporated herein by reference as a whole).

[0180] Another exemplary approach to determining the blanking threshold may be based on the sum of total electron counts across all detector segments (or a given subset). At the theoretical limit of 100% quantum efficiency (where virtually every electron impacting the sample is counted in a given detector), this counting method may have the effect of eliminating inter-pixel inflections of the incident electron beam current. These inflections can arise from at least two distinctly different sources. The first is instability in the electron source. Some types of electron guns experience small current inflections on microsecond, millisecond, or longer scales. The second is from the statistical nature of the particle beam in the form of Poisson noise (also called "counting statistics" or "shot noise"), and thus, if N electrons impact the sample on average during each residence time, there is (usually) an unavoidable statistical inflection of ±√N at each pixel. Many STEMs include noise reduction features, where a sample of the beam current is measured during scanning, and this signal (after fairly strong low-pass filtering) is used to digitally adjust the image to compensate for variations in electron illumination intensity. If virtually all electrons that collide with the sample within a single residence time are counted either directly or through integrated current measurements, and the source is blanked after a certain defined count n, both types of noise can be eliminated on a single-pixel basis.

[0181] In another embodiment for determining a blanking threshold, the method of the present disclosure may be extended to pixelated STEM. In pixelated STEM, a two-dimensional camera is positioned within a detection chamber, and diffraction images are read out at all probe positions (resulting in four-dimensional data). An additional explanation of pixelated STEM can be found, for example, in C. Ophus, "Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and beyond Basics of 4D-STEM", Microsc. Microanal. 1 (2019) (which is incorporated as a whole by reference).

[0182] In some cases, the controller may be configured to blank the primary beam when any one pixel reaches an event threshold, when a certain number / ratio of pixels reach this threshold, or when the total number of events across the detector reaches a certain threshold. Beyond pixelated stems, this approach may be applied to other techniques, such as event-driven binary ptychography. An additional explanation of event-driven binary ptychography can be found, for example, in "Fast Ptychographic Reconstruction for Sparse Binary Ptychography Data" by E. Hedley, B. Eckert, H. Soltau, and PD Nellist, Microsc. Microanal. 28, 438 (2022) (which is incorporated as a whole by reference).

[0183] Similarly, when a pixelated array is used for center-of-mass type imaging (COM), the beam may be blanked when enough electron detection events have been recorded to identify the center-of-mass vector to a certain acceptable angular precision limit.

[0184] Algorithmic thresholding—in some cases, a custom blanking threshold function may be tailored to a particular application. For example, these functions may be derived from empirical studies of specific types of samples. The functions may be implemented by firmware designed to be derived from empirical data. For example, when a user images a complex structure containing more than one material, some of the materials in the image may be of more interest to the user than others, and some may be more radiosensitive than others.

[0185] Figure 7 shows a hypothetical histogram of the ADF signal rate (relative probability) per pixel as a function of scattering rate for an exemplary sample. For example, suppose the user is more interested in low atomic number elements for a sample with the characteristics of Figure 7. The scattering rate peak 710 near zero may represent a nearly penetrating portion. Signals from this area may generally go unnoticed, but irradiating such a region can still cause damage through delocalization energy transfer, as is common in inelastic electron scattering. Peak 720 may represent low atomic number elements and may be of interest to the user in this hypothetical embodiment. Peak 730 may represent intermediate elements. These may be more radiosensitive components that the user may not be interested in in the embodiment. Peaks 740 and 750 may represent heavily scattering elements. Many signals from these elements may be present, and they may be easily recognizable due to their high signal strength. However, due to their high scattering probability, these peaks may allow for high energy transfer to the sample.

[0186] In the embodiment, the user may wish to determine the location of heavy elements, which can be recognized with a very short beam-on time per pixel. Furthermore, if the beam is over any intermediate elements, the beam may collide with, for example, a highly beam-sensitive insulator or a region of the sample that the user is not interested in.

[0187] In such cases, the arrival time of the first few electrons to reach the detector allows the user to have at least a reasonable degree of confidence regarding the peaks in the histogram that they are likely sampling at the current pixel. They may want to keep the beam on for 100% of the residence time in the "low atomic number elements" region 720, while stopping the beam relatively early if they are in the "empty space" 710 or "heavy elements" 740, 750 region, and stopping the beam very early if they are in the "intermediate elements" region 730.

[0188] A set of rules or instructions based on various information thresholds can be developed based on the information to be collected. For example, continuing with the embodiment in Figure 7, a set of rules such as the following can be established to improve the information-to-damage ratio for data acquisition. • If two or fewer events occur in the first half of the residence time, the beam will be stopped at the midpoint. This is likely to be empty space. • If 100 or more events occur within a single dwell time, the system will stop the beam when it has counted 100 events. This is likely due to heavy elements, and most of the available information from this pixel has probably already been obtained. If 3 to 5 events occur within the first 10% of the residence time, immediately stop the beam. There is a high probability that the beam is colliding with a radiation-sensitive intermediate-density material. Otherwise, keep the beam on for the entire dwell time and count the total signal.

[0189] In some cases, these rules may be implemented in a sequence generation algorithm that can both blank the beam at appropriate times and report externally the per-pixel electron detection rate (the number of detected electrons divided by the beam-on time) over either an analog or digital signal, which can be automatically recorded by the microscope's scanning control unit. This may produce a directly interpretable image.

[0190] Information-efficient imaging based on event threshold or event rate – Method 600 disclosed herein may generally be extended to electronic imaging. For example, Method 600 may further include the step of forming an image in response to a modulated electronic signal in a detector. In some cases, instead of recording the time to reach a threshold, the imaging method of the Disclosure may include the step of counting the number of events.

[0191] Figure 8 shows an exemplary method 800 of the present disclosure. Method 800 may include embodiments of a method for forming an image based on an electronic event signal.

[0192] Operation 810 of Method 800 may include a step of providing an informational threshold for a sample. In some cases, the threshold number of events may be the number of events in a single pixel. In some cases, the threshold number of events may be the average or sum of events across many pixels. In some cases, an event may be an electron collision. In some cases, an event may be a single count on an electron detector. In some cases, the signal on the detector may be an electron signal or electron-induced signal from the sample. In some cases, the step of determining whether a count has been achieved may be determined using an event signal processor such as those disclosed herein with respect to the "Event Signal Processor" section.

[0193] Thresholds may be determined by various techniques. For example, thresholds may be based on a damage threshold for a sample. Thresholds may be determined based on the information gain for pixels below a threshold. Thresholds may be determined experimentally. Thresholds may be set by the user. Thresholds may be varied by the user. Thresholds may be set using input from an information efficiency model. In some cases, the threshold number of events or threshold event rate is determined based on information about the sample. Thresholds may be determined by methods such as those described in the "Complex Thresholding" and / or "Algorithmic Thresholding" sections.

[0194] Operation 820 of Method 800 may include the step of collecting a number of events equal to an information threshold from a detector or determining that an event rate equal to an information threshold has been achieved. In some cases, the signal at the detector is an electronic signal or an electron-induced signal from the sample.

[0195] In some cases, method 800 may further include the step of collecting a threshold number of events from the detector or determining whether a threshold event rate has been achieved. In some cases, the signal in the detector may be an electronic signal from the sample or an electron-induced signal.

[0196] In operation 830 of method 800, the method may include a step of forming an image. The image-forming operation may include a step of forming an image based at least in part on an electronic signal or an electronically induced signal. For example, the method may include a step of forming an image based at least in part on the time to achieve a threshold number of events or a threshold event rate for a number of pixels. In some cases, the signal in the detector is an electronic signal or an electronically induced signal from the sample. For example, the electronic signal or electronically induced signal may be a single electronic signal.

[0197] In some cases, method 800 may further include a step of modulating the intensity of an electron source directed to a sample in response to determining that a threshold has been achieved. In some cases, a signal from an event signal processor may be transmitted to a controller comprising a driver electronics unit 120 and a digital pattern generator 130. In some cases, the modulation step includes the use of a deflector. For example, the digital pattern generator may control a deflector that switches the electron source according to a pattern of the pattern generator. The pattern generator may be a low-voltage signal that can be transmitted to the driver electronics unit. In some cases, the modulation step includes a step of moving the electron source to a different location on the sample. In some cases, the modulation step includes a step of turning off the electron source.

[0198] Driver electronics may take a low-voltage signal and convert it to a high-voltage signal, which may be used to apply the high voltage to a plate and deflect the electron beam. The sequence generator 140 of this disclosure may include a set of circuits or digital instructions on a controller for determining the waveform of the signal to be generated in the pattern generator. As disclosed herein, the waveform may be an arbitrary electron dose waveform. In some cases, the modulation step is performed substantially in real time. For example, real time may include a time substantially within the electron counting interval of the detector. Real time may refer to a response time of about 1 microsecond, 1 / 10 of a microsecond, 1 / 100 of a microsecond, 1 nanosecond, 1 / 10 of a nanosecond, 1 / 100 of a nanosecond, 1 picosecond, or less than that.

[0199] In some cases, the modulation step includes modulating the electron dose waveform, which is continuously updated based on the number of events determined from the signal. The electron dose waveform may have a continuously time-variable profile. In some cases, the electron dose waveform may have an arbitrarily defined time profile. For example, the arbitrarily defined time profile may have a time resolution of less than 10 nanoseconds (ns).

[0200] In some cases, the electron dose waveform comprises a series of intermediate points. In some cases, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some cases, the sequence comprises more than 1,000 intermediate points. In some cases, method 800 further includes the step of receiving an indication of an arbitrarily defined time profile from a user.

[0201] Information-efficient imaging based on the time to reach the threshold

[0202] Figure 9 shows an exemplary method 900 of the present disclosure. Method 900 may include embodiments of a method for forming an image based on an electronic event signal. For example, the approach disclosed herein may be extended to a plurality of detectors (or detectors comprising a plurality of segments).

[0203] Operation 910 of Method 900 may include the step of providing a threshold event count or threshold event rate for a first pixel on the detector. In some cases, the threshold event count may be the number of events at a single pixel. In some cases, the threshold event count may be the average or sum of events at many pixels. In some cases, the event may be an electron collision. In some cases, the event may be a single count at an electron detector. In some cases, the signal at the detector may be an electron signal or electron-induced signal from a sample. In some cases, the step of determining whether a count has been achieved may be determined using an event signal processor such as those disclosed herein with respect to the "Event Signal Processor" section.

[0204] The threshold may be determined by various techniques. For example, the threshold may be based on a damage threshold for the sample. The threshold may be determined based on the information gain of pixels below the threshold. The threshold may be determined experimentally. The threshold may be set by the user. The threshold may be varied by the user. The threshold may be set using input from an information efficiency model. In some cases, the threshold number of events or threshold event rate is determined based on information about the sample. The threshold may be determined by methods such as those described in the "Complex Thresholding" section. For example, in the exemplary algorithm in the "Complex Thresholding" section, an image with an intensity map of time to reach the threshold as a function of sample X and Y positions can effectively form a map of the types of elements present in the sample.

[0205] Operation 920 of Method 900 may include the step of recording the time to achieve a threshold number of events or a threshold event rate at a second pixel. In some cases, the second pixel is a pixel. In other cases, the second pixel is another pixel.

[0206] In some cases, method 900 may further include the step of collecting a threshold number of events or determining that a threshold event rate has been achieved from the detector. In some cases, the signal at the detector may be an electronic signal or an electron-induced signal from the sample. In some cases, method 900 may further include the step of forming an image based at least in part on the time to achieve a threshold number of events or a threshold event rate for a plurality of pixels. In some cases, the signal at the detector is an electronic signal or an electron-induced signal from the sample. For example, the electronic signal or electron-induced signal may be a single electronic signal.

[0207] In some cases, method 900 may further include a step of modulating the intensity of an electron source directed to a sample in response to determining that a threshold has been achieved. In some cases, a signal from an event signal processor may be transmitted to a controller comprising a driver electronics unit 120 and a digital pattern generator 130. In some cases, the modulation step includes the use of a deflector. For example, the digital pattern generator may control a deflector that switches the electron source according to a pattern of the pattern generator. The pattern generator may be a low-voltage signal that can be transmitted to the driver electronics unit. In some cases, the modulation step includes a step of moving the electron source to a different location on the sample. In some cases, the modulation step includes a step of turning off the electron source.

[0208] Driver electronics may take a low-voltage signal and convert it to a high-voltage signal, which may be used to apply the high voltage to a plate and deflect the electron beam. The sequence generator 140 of this disclosure may include a set of circuits or digital instructions on a controller for determining the waveform of the signal to be generated in the pattern generator. As disclosed herein, the waveform may be an arbitrary electron dose waveform. In some cases, the modulation step is performed substantially in real time. For example, real time may include a time substantially within the electron counting interval of the detector. Real time may refer to a response time of about 1 microsecond, 1 / 10 of a microsecond, 1 / 100 of a microsecond, 1 nanosecond, 1 / 10 of a nanosecond, 1 / 100 of a nanosecond, 1 picosecond, or less than that.

[0209] In some cases, the modulation step includes modulating the electron dose waveform, which is continuously updated based on the number of events determined from the signal. The electron dose waveform may have a continuously time-variable profile. In some cases, the electron dose waveform may have an arbitrarily defined time profile. For example, the arbitrarily defined time profile may have a time resolution of less than 10 nanoseconds (ns).

[0210] In some cases, the electron dose waveform comprises a series of intermediate points. In some cases, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some cases, the sequence comprises more than 1,000 intermediate points. In some cases, method 900 further includes the step of receiving an indication of an arbitrarily defined time profile from a user.

[0211] Use of an Information-Efficient Electron Imaging System - Figure 10 shows an exemplary method 1000 of the present disclosure. Method 1000 may include embodiments of a method for measuring an electronic signal or an electronically induced signal.

[0212] Operation 1010 of Method 1000 may include the step of providing a pattern generator configured to produce an electrical signal representing an electron dose waveform having a continuously variable time profile. The pattern generator may comprise an electron dose modulator 170. The pattern generator may comprise an electron dose modulator as described herein with respect to the "Electron Dose Modulator" section.

[0213] Operation 1020 of Method 1000 may include the step of providing an event signal processor configured to receive an electronic signal or an electronically induced signal from a detector and, in response, determine the number of electronic events on the detector based on the rising edge of the electronic signal or electronically induced signal in the detector, the event signal processor having a single event resolution. Event signal processor 150. The pattern generator may include an event signal processor as described herein with respect to the “Event Signal Processor” section.

[0214] In some cases, Method 1000 further includes the step of modulating the electron dose waveform based on the number of electron events. In some cases, Method 1000 further includes the step of performing any version of Method 600, 800, or 900 as disclosed herein.

[0215] Figure 12 shows an exemplary method 1200 of the present disclosure. Method 1200 may include embodiments of a method for measuring an electronic signal or an electronically induced signal.

[0216] Operation 1210 of Method 1200 may include the step of providing a logical condition relating to one or more measurements from an element, pixel, or portion of a detector, wherein the one or more measurements comprise an event count measurement of an electronic or ion signal or an electron-induced or ion-induced signal. In some cases, the condition code comprises a set of logical conditions. In some cases, the logical condition comprises one or a combination of event conditions as described herein with respect to the "Event Signal Processor" section. In some cases, one or a combination of event conditions comprises one or more threshold event counts. In some cases, one or a combination of event conditions comprises a threshold event rate. In some cases, one or a combination of event conditions comprises the absence of an event after a certain time period. In some cases, one or a combination of event conditions comprises measurements in multiple detectors or regions of a detector. In some cases, one or a combination of event conditions comprises multiple threshold event conditions, wherein each measurement in multiple detectors or regions of a detector comprises an associated threshold condition of the multiple threshold conditions. In some cases, one or a combination of event conditions comprises a comparison of measurements between multiple detectors or regions of a detector. In some cases, one or a combination of event conditions varies with position on the sample. In some cases, one or a combination of event conditions comprises an event or a measurement of an event. In some embodiments, one or a combination of event conditions comprises a mutual information threshold. In some cases, one or a combination of event conditions comprises an experimental signal.

[0217] Operation 1220 of Method 1200 may include a step of determining whether a logical condition is met based at least in part on one or more measurements.

[0218] In operation 1230 of method 1200, the method may include a step of modulating the intensity of an electron source or ion source directed to the sample in response to whether a logical condition is met. In some cases, the modulation is induced with a delay for a pixel residence time of less than 20 nanoseconds. In other cases, the modulation is induced with a delay for a pixel residence time of less than 50 nanoseconds. In other cases, the modulation is induced with a delay for a pixel residence time of less than 100 nanoseconds.

[0219] In some cases, operation 1230 further includes the step of moving the electron source or ion source to a different location on the sample. In some cases, operation 1230 further includes the step of turning off the electron source or ion source. In some cases, operation 1230 further includes the step of deflecting the path of the electron source or ion source. In some cases, operation 1230 is performed substantially in real time. In some cases, operation 1230 is performed within the electron counting interval of the detector.

[0220] In some cases, operation 1230 further includes the step of modulating an electron or ion dose waveform based at least in part on one or more measurements. In some embodiments, the electron or ion dose waveform has a continuously variable time profile. In some cases, the electron or ion dose waveform has an arbitrarily defined time profile. For example, the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns). In some cases, the method further includes the step of receiving an indication of the arbitrarily defined time profile from a user. In some cases, the electron or ion dose waveform has a series of intermediate points. For example, the series of intermediate points has more than 1,000 intermediate points. In some cases, the series of intermediate points can be selected individually or collectively to construct an arbitrarily defined time profile. In some cases, the electron dose waveform may have a waveform such as those described herein with respect to the "Electron Dose Modulator" section.

[0221] In some cases, Method 1200 further includes the step of recording the time it takes for a pixel, element, or portion of the detector to achieve a logical condition. In some embodiments, Method 1200 further includes the step of collecting a determination of whether the logical condition is met, such that the electron or ion signal or electron-induced or ion-induced signal is from or through the sample.

[0222] Figure 13 shows an exemplary method 1300 of the present disclosure. Method 1300 may include embodiments of a method stored on a non-transient computing device-readable medium and may be executable by a processor.

[0223] Operation 1310 of Method 1300 may include the step of receiving a condition code. In some cases, the condition code comprises a reference to a lookup table describing a set of logical conditions. In other cases, the condition code comprises a set of logical conditions. In other cases, the logical conditions comprise one or a combination of event conditions as described herein with respect to the “Event Signal Processor” section.

[0224] Operation 1320 of Method 1300 may include the step of receiving a signal corresponding to an electronic signal or an electronically induced signal from a sample.

[0225] Operation 1330 of Method 1300 may include the step of comparing the received signal with a condition code.

[0226] Operation 1330 of Method 1300 may include a step of determining whether an output signal should be transmitted, at least in part, based on a comparison of a received signal and a condition code. In some cases, the output signal comprises a trigger signal. In some cases, the trigger signal comprises a delay for a pixel residence time of less than 20 nanoseconds. In some cases, modulation is induced with a delay for a pixel residence time of less than 50 nanoseconds. In some cases, modulation is induced with a delay for a pixel residence time of less than 100 nanoseconds. In some cases, the output signal comprises an electrical signal representing an electron dose waveform. In some cases, the electron dose waveform comprises a waveform as described herein with respect to the "Electron Dose Modulator" section. Purpose

[0227] Spectroscopy—The devices and methods disclosed herein may be used in spectroscopic applications. For example, a STEM may be equipped with one or more spectrometers. One or more spectrometers may include an energy-dispersive X-ray spectrometer (EDX), an electron energy loss spectrometer (EELS), etc. In various spectroscopic applications, including, but not limited to, EDX and EELS, the collected spectral data may be integrated within the pixel residence time and assembled into a three-dimensional data cube (e.g., two spatial dimensions and one energy dimension). In combination with the devices and methods disclosed herein, the illumination duration of each pixel may vary from pixel to pixel. For example, in event-stream EELS spectroscopy, the electron dose modulation techniques disclosed herein may be integrated with the event-stream recording process. For illustrative purposes, an example of an event-stream-based EELS is disclosed, for example, in "Event-Based Hyperspectral EELS: Towards Nanosecond Temporal Resolution" (undated) by Y. Auad, M. Walls, J.-D. Blazit, O. Stephan, HG Tizei, M. Kociak, F. De La Pena, and M. Tence.

[0228] Damage Mechanisms – The devices and methods disclosed herein may be used to understand damage mechanisms. In some cases, electrons colliding with a certain detector segment or set of segments (e.g., in a pixelated STEM) are correlated with a certain damage mechanism. Avoiding such damage mechanisms may be advantageous. In response, electrons colliding with the detector at a higher level in determining the electron counting blanking threshold may be weighted. The correlation may be either direct or indirect. For example, electrons colliding with high atomic number atoms may be more likely to undergo both high-angle scattering events and the imparting of a large amount of energy to the material (which can lead to various forms of sample damage). For example, high-angle scattering events may be detected using a high-angle annular dark-field (HAADF) detector, while the imparting of energy may be detected spectroscopically. Either type of detector may be used to set a threshold for blanking the beam. In scanning materials with mixtures of high and low atomic numbers, imaging both heavy and light elements without introducing an unacceptable amount of radiation damage may be a challenge. For example, if the beam current is high enough to image light elements, the total energy absorption can be excessive, and the sample can be damaged. The proposed system can automatically reduce irradiation of heavy elements, which have both ease of visualization (e.g., require less irradiation for proper signal acquisition) and a tendency to scatter and absorb energy from a large number of electrons. This strategy can reduce the energy imparted to the sample without losing much information about the sample, as the detected electrons arriving at high speed will quickly enter a stage of diminishing yield. Conversely, this approach can automatically increase the exposure time for regions with lower atomic numbers. Dim, low-contrast regions that are otherwise difficult to image can become much more accessible through this technique. The ability to visualize light elements in such materials has long been a major challenge in electron microscopy.

[0229] As an example, an ADF or HAADF detector may be used with a low count threshold n for blanking the beam while performing so-called "low-loss electron energy loss spectral imaging" of a nanostructured material suspended in empty space. Here, when the electron beam is not colliding with the sample at all, a higher beam current (e.g., a full beam current) may be used, and thus the so-called "alloof EELS" method may be used to image surface electromagnetic excitations. Conversely, as soon as this collides with the material itself, a lower beam current (e.g., the beam may be almost completely stopped) may be used. Using the algorithmic thresholding approach disclosed herein, this adjustment may occur automatically pixel by pixel during scanning, even if the sample has substantially moved / drifted during the measurement.

[0230] For illustrative purposes, examples of the "Aloof EELS" method are provided, for example, in "Damage-Free Vibrational Spectroscopy of Biological Materials in the Electron Microscope" by P. Rez, T. Aoki, K. March, D. Gur, OL Krivanek, N. Dellby, TC Lovejoy, SG Wolf, and H. Cohen, Nat. Commun. 2016 71 7, 1 (2016) and in "Vibrational and Valence Aloof Beam EELS: A Potential Tool for Nondestructive Characterization of Nanoparticle Surfaces" by PA Crozier, Ultramicroscopy 180, 104 (2017) (each of which is incorporated herein by reference as a whole).

[0231] For illustrative purposes, examples of drift correction are provided, for example, in "Identifying and Correcting Scan Noise and Drift in the Scanning Transmission Electron Microscope" by L. Jones and PD Nellist, Microsc. Microanal. 19, 1050 (2013), and in "Revolving Scanning Transmission Electron Microscopy: Correcting Sample Drift Distortion without Prior Knowledge" by X. Sang and JM LeBeau, Ultramicroscopy 138, 28 (2014) (each of which is incorporated herein by reference as a whole).

[0232] For illustrative purposes, examples of non-rigid alignment are provided, for example, in "Optimized Imaging Using Non-Rigid Registration" by B. Berkels, P. Binev, DA Blom, W. Dahmen, RC Sharpley, and T. Vogt, Ultramicroscopy 138, 46 (2014) and in "Smart Align - a New Tool for Robust Non-Rigid Registration of Scanning Microscope Data" by L. Jones, H. Yang, TJ Pennycook, MSJ Marshall, S. Van Aert, ND Browning, MR Castell, and PD Nellist, Adv. Struct. Chem. Imaging 1, 8 (2015) (each of which is incorporated herein by reference as a whole). Computer system

[0233] This disclosure provides a computer system programmed to implement the methods disclosed herein. Figure 11 shows a computer system 1101 programmed or otherwise configured to implement the methods and systems disclosed herein. The computer system 1101 can coordinate various aspects of a controller, event signal processor, electron dose modulator, driver electronics, digital pattern generator, sequence generation algorithm, or combination thereof, for example, to provide or implement instructions to one or more operations of methods 600, 800, 900, 1000, 1200, or 1300 disclosed herein, or combinations thereof. The computer system 1101 may be a computer system located remotely from a user's electronic device. The electronic device may be a mobile electronic device. The electronic device may be an embodiment of a controller 160 as disclosed herein.

[0234] In some cases, the component-driven electronics 120, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 may individually or collectively comprise the controller 160 of the Disclosure. In some cases, signals from the event signal processor may be transmitted to a controller comprising the driver electronics 120 and the digital pattern generator 130. In some cases, the controller may also comprise one or more embodiments of the event signal processor 150 of the Disclosure. In some cases, the controller may comprise one or more processors. In some cases, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 may collectively comprise the electron dose modulator 170 of the Disclosure. In some cases, the controller may comprise one or more field-programmable gate arrays (FPGAs) or one or more ASICs. In some cases, the first field-programmable gate array is configured to control a deflector. For example, the FPGA or ASIC may comprise the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150. In some cases, the drive electronics 120 are substantially analog, and the digital pattern generator 130 and sequence generation algorithm 140 are part of an FPGA or ASIC. In other cases, the event signal processor 150 includes a second field-programmable gate array configured to control the detector.

[0235] In some cases, the digital pattern generator 130, the sequence generation algorithm 140, and the event signal processor 150 are provided by an FPGA or ASIC, while the drive electronics 120 remain separate. For example, the drive electronics 120 may include a higher voltage switching circuit for the deflector and may be separately shielded from lower voltage components.

[0236] This disclosure provides a system comprising a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). The FPGA or ASIC comprises programmable logic blocks, programmable interconnects, etc., configured to implement any of the methods described above or elsewhere herein. The system may also comprise one or more computer processors and computer memory coupled thereto. The one or more computer processors may be configured to provide information to the FPGA or ASIC in order to implement any of the methods described above or herein.

[0237] The systems and methods of this disclosure may include a scanning controller 180. The scanning controller 180 may include an embodiment of a processor or computer system as disclosed herein. In some cases, the scanning controller can control and / or direct instructions to one or more components of the electron dose modulator or controller herein. In some cases, the scanning controller 180 includes a computer system, e.g., a computer system operable by a user. The scanning controller may be configured to control various computing components. For example, the scanning controller may send and receive instructions to and from the FPGA or ASIC of this disclosure. FPGA implementations as disclosed herein may or may not have a CPU. In some cases, the CPU disclosed herein may be used for communication and configuration, while the FPGA may be involved in real-time signal processing.

[0238] In some embodiments, the computer system 1101 includes a central processing unit (CPU, also referred to herein as "processor" and "computer processor") which may be a single-core or multi-core processor, or multiple processors for parallel processing. The computer system 1101 also includes memory or memory locations 1110 (e.g., random-access memory, read-only memory, flash memory), an electronic storage unit 1115 (e.g., a hard disk), a communication interface 1120 for communicating with one or more other systems (e.g., a network adapter), and peripheral devices 1125 such as a cache, other memory, data storage devices, and / or an electronic display adapter. The memory 1110, storage unit 1115, interface 1120, and peripheral devices 1125 communicate with the CPU 1105 through a communication bus (solid line), such as a motherboard. The storage unit 1115 may be a data storage unit (or data repository) for storing data. The computer system 1101 can be operationally coupled to a computer network ("network") 1130 using the communication interface 1120. Network 1130 may be the Internet, an intranet and / or extranet, or an intranet and / or extranet communicating with the Internet. Network 1130 may, in some cases, be a telecommunications and / or data network. Network 1130 may include one or more computer servers that can enable distributed computing such as cloud computing. Network 1130 may, in some cases, implement a peer-to-peer network that can use computer system 1101 to enable devices connected to computer system 1101 to behave as clients or servers.

[0239] The CPU 1105 can execute a sequence of machine-readable instructions, which may be embodied in a program or software. Instructions may be stored in a memory location, such as memory 1110. Instructions can be directly directed to the CPU 1105, which can then be programmed or otherwise configured to implement the methods of this disclosure. Embodiments of operations performed by the CPU 1105 may include fetching, decoding, executing, and writing back.

[0240] The CPU 1105 may be part of a circuit such as an integrated circuit. One or more other components of system 1101 may be included in the circuit. In some cases, the circuit is an application-specific integrated circuit (ASIC).

[0241] The storage unit 1115 can store files such as drivers, libraries, and saved programs. The storage unit 1115 can also store user data, such as user preferences and user programs. The computer system 1101 may include one or more additional data storage units located outside the computer system 1101, such as on a remote server that communicates with the computer system 1101 via an intranet or the internet.

[0242] Computer system 1101 can communicate with one or more remote computer systems via network 1130. For example, computer system 1101 can communicate with a user's remote computer system. Embodiments of remote computer systems include personal computers (e.g., portable PCs), slate or tablet PCs (e.g., Apple® iPad®, Samsung® Galaxy Tab), telephones, smartphones (e.g., Apple® iPhone®, Android® compatible devices, Blackberry®), or personal digital assistants. Users can access computer system 1101 via network 1130.

[0243] Machine-executable code—methods as described herein can be implemented using machine (e.g., computer processor) executable code stored on an electronic storage location of the computer system 1101, such as memory 1110 or electronic storage unit 1115. The machine-executable or machine-readable code can be provided in software form. During use, the code can be executed by the processor 1105. In some cases, the code can be read from the storage unit 1115 and stored on memory 1110 for quick access by the processor 1105. In some situations, the electronic storage unit 1115 can be omitted, and the machine-executable instructions are stored on memory 1110.

[0244] The code can be pre-compiled and configured for use with machines that have processors adapted to run the code, or it can be compiled during runtime. The code can be supplied in a programming language that can be chosen to enable the code to be executed in a pre-compiled or as-compiled manner.

[0245] Aspects of the systems and methods provided herein, such as computer system 1101, can be embodied in programming. Various aspects of the technology can typically be considered “products” or “manufactured goods” in the form of machine (or processor) executable code and / or associated data carried on or embodied thereon on a certain type of machine-readable medium. Machine-executable code can be stored on electronic storage units such as memory (e.g., read-only memory, random-access memory, flash memory) or hard disks. The “storage” type medium can include any or all of the tangible memory of a computer, processor, or equivalent, or their associated modules such as various semiconductor memories, tape drives, disk drives, and equivalents, which can provide non-transient storage at any given time for software programming. All or part of the software may be communicated from time to time through the Internet or various other telecommunication networks. Such communication may enable, for example, the loading of software from one computer or processor to another, for example, from a management server or host computer to an application server computer platform. Therefore, other types of media that may carry software elements include optical, electrical, and electromagnetic waves, such as those used across physical interfaces between local devices, through wired and optical fixed networks, and via various air links. Physical elements that carry such waves, such as wired or wireless links, optical links, or equivalents, may also be considered media that carry software. Unless limited to non-transient tangible “storage” media as used herein, the terms computer or machine-readable media, etc., refer to any medium involved in providing instructions to a processor for execution.

[0246] Therefore, machine-readable media such as computer executable code may take many forms, but are not limited to, tangible storage media, carrier media, or physical transmission media. Non-volatile storage media include optical or magnetic disks, such as any storage device in any computer or equivalent, such as those shown in the drawings, which may be used to implement databases, etc. Volatile storage media include dynamic memory, such as the main memory of such a computer platform. Tangible transmission media include copper wires and optical fibers, such as coaxial cables, i.e., wires that form buses in computer systems. Carrier media may take the form of electrical or electromagnetic signals, or acoustic or optical waves, such as those generated between radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs or DVD-ROMs, any other optical media, punched card paper tapes, any other physical storage media with perforation patterns, RAM, ROMs, PROMs and EPROMs, FLASH®-EPROMs, any other memory chips or cartridges, carriers for transporting data or instructions, cables or links for transporting such carriers, or any other media from which a computer can read programming code and / or data. Many of these forms of computer-readable media may be involved in transporting one or more sequences of one or more instructions to a processor for execution.

[0247] The computer system 1101 includes, or can communicate with, an electronic display 1135, which has a user interface (UI) 1140. Embodiments of the UI include, but are not limited to, a graphical user interface (GUI) and a web-based user interface.

[0248] Algorithms - The methods and systems of this disclosure can be implemented using one or more algorithms. The algorithms can be implemented using software in response to execution by the central processing unit 1105. In some cases, the algorithms can be implemented using the field-programmable gate array of this disclosure or a plurality of field-programmable gate arrays.

[0249] In some cases, the algorithm may comprise a sequence generation algorithm 140. The sequence generation algorithm may be an algorithm capable of forming an indication of the electron dose waveform of the Disclosure. The sequence generation algorithm may take into account one or more parameters. In some cases, the sequence generation algorithm may be an algorithm capable of taking into account one or more of the following in order to form an indication of the electron dose waveform of the Disclosure: information about the sample, deflection equipment, detectors involved in the measurement, and determined waveforms input to the control software by the user. The algorithm may perform, for example, one or more of the operations disclosed herein with respect to the “algorithmic thresholding” section.

[0250] For example, the shape of the electron dose waveform may be adjusted according to one or more parameters. In some cases, it may be advantageous to continuously adjust the waveform characteristics, such as the waveform's time profile, according to the image, deflector, driver, detector, or waveform properties, in order to improve measurement quality, respond to external changes in the instrument, or both. Automatic updating of the waveform's time profile can simplify the user experience by compensating for changes in measurement conditions or by automatically inputting improved measurement settings.

[0251] For example, one or more parameters may provide information about one or more of the following: the properties of the image from the detector, the properties of the deflector, the properties of the driver electronics, the properties of the detector, and the indication of the electron dose waveform. In some cases, one or more parameters may provide minimum, maximum, or fixed value indications of the pulse width or pulse repetition rate of the electron dose waveform. For example, the waveform may be adjusted so that the waveform indication by the user does not exceed the functional capabilities of the device. In some cases, the waveform indication cannot exceed a fixed waveform parameter set by the user, for example, so that the ramp voltage does not exceed a set level.

[0252] In some cases, one or more parameters provide timing constraints for the deflector, driver electronics, or pattern generator. For example, the deflector may be timed so that electrons can pass through the detector during the detector's acquisition interval. For example, the deflector's pattern generator may be timed so that electrons pass through the detector during the acquisition interval. For example, the deflection may be synchronized with the readouts from the detector over a long time period. The time period may be, for example, a data acquisition period of up to 8 hours or longer. The timing of the deflector and detector may be such that the timing accuracy of the two processes meets a defined performance specification, for example, the synchronization of the two processes is within 50 milliseconds or better.

[0253] In some cases, one or more parameters have a characteristic timescale of the sample or processes within the sample. For example, electron dose may deform and move the sample, or accumulate heat or net charge in the sample, each of which may lead to a blurred image. In some cases, the structure of the sample may be altered, and therefore the original structure of interest may no longer be visible. Each of these processes may have a characteristic timescale. For example, the effect of electron dose on a sample may occur at the start of exposure, or may appear over a limited time after the electron beam first touches the sample. These effects may be reduced or disappear at a later point in time after exposure. Therefore, the electron dose waveform may be automatically adjusted, for example, by slowly varying the electron dose over time. Varying the dose over time may give the sample an opportunity to adjust as the dose increases or decreases. In another embodiment, the effects of dose may be mitigated by controlling the duration of short, repeated exposures.

[0254] In some cases, one or more parameters include a time-dependent voltage bias or temperature. For example, a voltage bias or temperature may be applied to the sample by a sample holder, which can alter the optimal dose waveform. For example, an electron dose may cause heat or net charge to accumulate in the sample, each of which may lead to a blurred image. For example, the temperature of the sample or instrument may drift, and the waveform may be adjusted to respond. The waveform may be adapted to increase or decrease the average dose in order to limit induced voltage or current changes, or in response to changes in the signal or sample based on heat or charge fluctuations.

[0255] In some cases, one or more parameters include detector dose rate or timing considerations. For example, a deflector may be timed so that electrons can pass through the detector during the detector's acquisition interval. For example, a waveform may be synchronized with readouts from the detector over a long time period. The time period may be, for example, a data acquisition period of up to 8 hours or longer. The timing of the waveform and detector may be such that the timing accuracy of the two processes meets a defined performance specification, for example, the synchronization of the two processes is within 50 milliseconds or better.

[0256] In some cases, one or more parameters indicate the quality of the data signal from collected or real-time measurements. In other cases, one or more parameters indicate the effect of the intensity of the electron dose waveform on the sample from collected or real-time measurements. In some cases, the dose effect may reduce the quality of the data. This may be due, for example, transient charge and / or sample motion, although this is not limited by theory. In some cases, it may be advantageous to automatically adjust one or more parameters of the electron dose in response to real-time images.

[0257] Preferred embodiments of the present invention are shown and described herein, but it will be apparent to those skilled in the art that such embodiments are provided only as examples. The present invention is not intended to be limited by the specific examples provided herein. While the present invention is described with reference to the preceding specification, the descriptions and illustrations of embodiments herein are not intended to be constrained. Numerous variations, modifications, and substitutions will be recalled herein by those skilled in the art without departing from the present invention. Furthermore, it should be understood that all aspects of the present invention are not limited to the specific descriptions, configurations, or relative proportions described herein, depending on various conditions and variables. It should be understood that various alternatives to the embodiments of the present invention described herein may be employed in practicing the present invention. Therefore, it is assumed that the present invention also covers any such alternatives, modifications, variations, or equivalents. The following claims define the scope of the present invention, and methods and structures within the scope of these claims, as well as their equivalents, are intended to be covered thereby.

Claims

1. A method for measuring an electronic signal or an electronically induced signal, wherein the method is (a) Providing a threshold number of events or threshold event rate for an element, pixel, or part of a detector; (b) A step of collecting the threshold number of events from the detector or determining that the threshold event rate has been achieved, wherein the signal in the detector is an electronic signal or an electronically induced signal from the sample, (c) A step of modulating the intensity of an electron source or ion source directed at the sample in response to the collecting step in (b) Methods that include...

2. (c) The method according to claim 1, further comprising the step of directing the electron source or the ion source to another location on the sample.

3. (c) The method according to claim 1, further comprising the step of turning off the electron source or the ion source.

4. (c) The method according to claim 1, further comprising the step of deflecting the path of the electron source or the ion source.

5. (c) The method according to claim 1, which is carried out in substantially real time.

6. (c) The method according to claim 1, wherein the method is performed within the electronic counting interval of the detector.

7. The method according to claim 1, wherein the threshold number of events or the threshold event rate is determined at least in part based on information about the sample.

8. (c) The method according to claim 1, further comprising the step of modulating an electron dose waveform or an ion dose waveform based at least in part on the number of events determined from the signal.

9. The method according to claim 8, wherein the electron dose waveform or ion dose waveform has a continuously variable time profile.

10. The method according to claim 9, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

11. The method according to claim 10, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

12. The method according to claim 10, further comprising the step of receiving an indication of the arbitrarily defined time profile from a user.

13. The method according to claim 8, wherein the electron dose waveform or ion dose waveform comprises a series of intermediate points.

14. The method according to claim 13, wherein the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile.

15. The method according to claim 13, wherein the series of intermediate points comprises more than 1,000 intermediate points.

16. The method according to claim 1, further comprising the step of recording the time to achieve the threshold number of events or the threshold event rate in a pixel, element, or portion of the detector.

17. The method according to claim 16, further comprising the step of forming an image based at least partially on the time to achieve the threshold number of events or the threshold event rate with respect to a plurality of pixels, elements, or portions of the detector.

18. The method according to claim 16, further comprising the steps of collecting the threshold number of events from the detector or determining that the threshold event rate has been achieved, wherein the signal in the detector is an electron signal or ion signal or an electron-induced signal or an ion-induced signal from or through the sample.

19. The method according to claim 1, wherein the threshold number of events or the threshold rate of events is a mutual information threshold.

20. The method according to claim 1, further comprising the step of providing the threshold number of events or the threshold event rate with respect to a second element or second portion of the detector, following (c).

21. A method for forming an image based on an electronic event signal, wherein the method is (a) Providing a threshold number of events or threshold event rate relating to a first element or part of the detector, (b) The step of recording the time until the threshold number of events or the threshold event rate is achieved in the second element or part of the detector. Methods that include...

22. The method according to claim 21, wherein the second element or part is the element or part.

23. The method according to claim 21, wherein the second element or part is another element or part.

24. The method according to claim 21, further comprising the step of forming an image based at least partially on the time to achieve the threshold number of events or the threshold event rate with respect to a plurality of elements or parts of the detector.

25. The method according to claim 21, wherein the signal in the detector is an electronic signal or an electron-induced signal from the sample.

26. The method according to claim 25, wherein the electronic signal or the electron-induced signal is a single electronic signal.

27. (c) The method according to claim 21, further comprising the steps of collecting the threshold number of events from the detector or determining that the threshold event rate has been achieved.

28. The method according to claim 27, further comprising the step of modulating the intensity of an electron source or ion source directed to the sample in response to the collecting step in (d)(c).

29. (d) The method of claim 28, comprising the step of deflecting the electron source to another location on the sample.

30. The method according to claim 28, wherein (d) is the step of turning off the electron source or the ion source.

31. (d) The method according to claim 28, comprising the step of deflecting the path of the electron source or the ion source.

32. (d) The method of claim 28, which is carried out substantially in real time.

33. (d) The method of claim 28, wherein the method is performed within the event counting interval of the detector.

34. The method according to claim 28, wherein the threshold number of events or the threshold event rate is determined based on information about the sample.

35. The method according to claim 28, wherein (d) modulates an electron dose waveform or an ion dose waveform, the electron dose waveform being continuously updated based on the number of events determined from the signal.

36. The method according to claim 35, wherein the electron dose waveform or ion dose waveform comprises a continuously variable time profile.

37. The method according to claim 36, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

38. The method according to claim 37, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

39. The method according to claim 37, further comprising the step of receiving an indication of the arbitrarily defined time profile from a user.

40. The method according to claim 35, wherein the electron dose waveform or ion dose waveform comprises a series of intermediate points.

41. The method according to claim 40, wherein the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile.

42. The method according to claim 40, wherein the series comprises more than 1,000 intermediate points.

43. A method for forming an image based on an electronic event signal, wherein the method is (a) A step of providing an information threshold for the sample, (b) A step of collecting a number of events equal to the information threshold from the detector or a step of determining that an event rate equal to the information threshold has been achieved, wherein the signal in the detector is an electronic signal or an electronically induced signal from the sample, (c) The step of forming an image based at least partially on the electronic signal or the electron-induced signal. Methods that include...

44. The method according to claim 43, wherein the information threshold for the sample is based on the sum of the total electronic counts across the sample.

45. The method according to claim 43, wherein the electronic signal or the electron-induced signal is a single electronic signal.

46. The method according to claim 43, further comprising the step of recording the time it takes to achieve the threshold number of events or the threshold rate of events in the pixel.

47. The method of claim 43, further comprising the step of modulating the intensity of an electron source or ion source directed to the sample in response to the collecting step in (d)(b).

48. The method according to claim 47, wherein (d) the step of moving the electron source or the ion source to another location on the sample.

49. The method according to claim 47, wherein (d) is the step of turning off the electron source or the ion source.

50. (d) The method according to claim 47, comprising the step of deflecting the path of the electron source or the ion source.

51. (d) The method of claim 47, which is carried out substantially in real time.

52. (d) The method according to claim 51, which is performed within the electronic counting interval of the detector.

53. The method according to claim 47, wherein the threshold number of events or the threshold event rate is determined based on information about the sample.

54. The method according to claim 47, wherein (d) modulates an electron or ion dose waveform, the electron dose waveform being continuously updated based on the number of events determined from the signal.

55. The method according to claim 54, wherein the electron dose waveform or ion dose waveform comprises a continuously variable time profile.

56. The method according to claim 55, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

57. The method according to claim 56, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

58. The method according to claim 56, further comprising the step of receiving an indication of the arbitrarily defined time profile from a user.

59. The method according to claim 54, wherein the electron dose waveform or ion dose waveform comprises a series of intermediate points.

60. The method according to claim 59, wherein the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile.

61. The method according to claim 59, wherein the series comprises more than 1,000 intermediate points.

62. A method for measuring an electronic signal or an electronically induced signal, wherein the method is (a) Providing a pattern generator configured to produce an electrical signal representing an electron dose waveform or ion dose waveform having a continuously variable time profile, (b) Providing an event signal processor configured to receive an electronic signal or an electronically induced signal from a detector and, in response, determine the number of electronic events on the detector based on the rising edge of the electronic signal or the electronically induced signal in the detector, wherein the event signal processor has a single event resolution, and Methods that include...

63. The method according to claim 62, further comprising the step of modulating the electron / ion signal based on the number of electron events.

64. The method of claim 62, further comprising the step of carrying out the method of any of the preceding claims.

65. A device comprising a controller, the controller comprising a non-transient storage medium having instructions stored thereon, the instructions being configured to carry out the method of any of the preceding claims when executed by the controller.

66. A device, wherein the device is A deflector positioned between an electron source or ion source and a sample area, wherein the deflector modulates the intensity of the electron source or ion source directed towards the sample area according to an electron dose waveform or ion dose waveform having a continuously variable time profile. A detector configured to receive an electronic signal or an electronically induced signal related to the sample area, wherein an electronic event on the detector is correlated to the rising edge of the electronic signal or the electronically induced signal in the detector, A controller operably coupled to the deflector and the detector, wherein the controller is configured to determine the continuous variable time profile in response to the electronic event. A device equipped with the following features.

67. The device according to claim 66, wherein the controller comprises one or more field-programmable gate arrays.

68. The device according to claim 67, comprising a first field-programmable gate array configured to control the deflector.

69. The device according to claim 67, comprising a first field-programmable gate array configured to control the detector.

70. The device according to claim 66, further comprising an event signal processor configured to receive an electronic signal or an electronically induced signal from a detector and, in response, determine the number of electronic events on the detector based on the rising edge of the electronic signal or the electronically induced signal in the detector.

71. The device according to claim 70, wherein the event signal processor is part of the controller.

72. The device according to claim 70, wherein the event signal processor is separate from the controller.

73. The event signal processor comprises a single event resolution, according to claim 70.

74. The device according to claim 70, wherein the event signal processor is configured to determine the gradient of the electronic signal or the electronically induced signal.

75. The device according to claim 74, wherein the electronic event is correlated with the gradient exceeding a threshold gradient value.

76. The device according to claim 70, further comprising a scintillator, wherein a scintillation signal is generated in response to the electronic signal or the electronically induced signal, and the event signal processor is configured to receive the scintillation signal.

77. The device according to claim 70, wherein the event signal processor comprises an output signal, the output signal being operably coupled to the controller for determining the continuous variable time profile.

78. The device according to claim 77, wherein the output signal is an instantaneous trigger signal.

79. The device according to claim 66, wherein the controller is configured to determine the time to keep the electronic signal ON in response to the electronic event signal.

80. The device according to claim 66, wherein the continuously variable time profile is modulated in real time.

81. The device according to claim 66, wherein the continuous variable time profile is modulated within the electronic counting interval of the detector.

82. The device according to claim 66, wherein the detector comprises a plurality of detectors or detector segments.

83. The device according to claim 66, wherein the detector comprises an image sensor.

84. The device according to claim 66, wherein the detector comprises a single-channel detector.

85. The device according to claim 66, wherein the detector is a multi-channel detector.

86. The device according to claim 66, wherein the device is configured to detect in parallel from a plurality of channels.

87. The device according to claim 66, wherein the waveform comprises a series of intermediate points.

88. The device according to claim 87, wherein the series comprises more than 1,000 intermediate points.

89. The device according to claim 66, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

90. The device according to claim 89, wherein the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile.

91. The device according to claim 89, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

92. The device according to claim 89, wherein the arbitrarily defined time profile is indicated by the user.

93. The device according to claim 66, wherein the deflector comprises a driving electrode and an electrode for a fixed voltage.

94. The device according to claim 66, wherein the deflector comprises two drive electrodes.

95. The device according to claim 66, wherein the electron dose waveform or ion dose waveform modulates the average intensity of the electron source or ion source directed toward the sample area.

96. The device according to claim 95, wherein the average intensity is modulated substantially without altering other image conditions.

97. The device according to claim 95, wherein the average intensity is controllable independently of the driving voltage of the electron source or the ion source.

98. The device according to claim 95, wherein the average intensity is continuously variable over a range of 0 to 100% dose transmission.

99. The device according to claim 66, wherein the electron dose waveform or ion dose waveform comprises a periodic waveform.

100. The device according to claim 66, wherein the electron dose waveform or ion dose waveform is non-periodic.

101. The device according to claim 66, wherein the electron dose waveform or ion dose waveform comprises a pump pulse and a probe pulse.

102. The device according to claim 66, wherein the electron dose waveform or ion dose waveform is a square wave.

103. The device according to claim 102, wherein the transition time between high voltage and low voltage is less than approximately 50 nanoseconds (ns) and is defined as the sum of ringing time and slope time.

104. The device according to claim 102, wherein the transition time between high voltage and low voltage is less than about 10 nanoseconds (ns) and is defined as the slope time of the transition voltage from about 10% to about 90%.

105. The device according to claim 102, wherein the pulse width of the square wave is aperiodic.

106. The device according to claim 66, wherein the electron dose waveform or ion dose waveform has a minimum exposure time of approximately 100 nanoseconds (ns).

107. A pattern generator configured to produce an electrical signal representing the electron dose waveform or ion dose waveform, A driver electronic device configured to receive the electrical signal from the pattern generator and to supply a voltage having the electron dose waveform or ion dose waveform to the deflector, The device according to claim 66, further comprising:

108. The method further comprises one or more computer processors equipped with instructions, wherein when an instruction is executed, Receiving indication of the aforementioned electron dose waveform or ion dose waveform, To deliver the indication to the pattern generator The device according to claim 107, configured to perform the following:

109. A method for measuring an electronic signal or an electronically induced signal, comprising the step of providing a device according to any one of claims 66 to 108.

110. A method for measuring an electronic signal or an electronically induced signal, wherein the method is (a) Providing an information threshold for an element or part of the detector, (b) A step of determining that the information threshold is achieved, wherein the signal in the detector is an electronic signal or an electron-induced signal from the sample, (c) A step of modulating the intensity of an electron source or ion source directed at the sample in response to the collecting step in (b) Methods that include...

111. The method according to claim 110, further comprising the step of providing the device according to any one of claims 66 to 106.

112. (c) The method according to claim 110, comprising the step of moving the electron source or the ion source to another location on the sample.

113. (c) The method according to claim 110, comprising the step of turning off the electron source or the ion source.

114. (c) The method according to claim 110, comprising the step of deflecting the path of the electron source or the ion source.

115. (c) The method of claim 110, which is carried out substantially in real time.

116. (c) The method according to claim 110, which is performed within the electronic counting interval of the detector.

117. A method for measuring an electronic signal or an electronically induced signal, wherein the method is (a) Providing logical conditions relating to one or more measurements from an element, pixel, or part of a detector, wherein the one or more measurements comprise an event count measurement of an electronic signal or an ion signal or an electron-induced signal or an ion-induced signal; (b) A step of determining whether the logical condition is met, based at least in part on one or more measurements, (c) In response to the determination step in (b), a step of modulating the intensity of an electron source or ion source directed at the sample; Methods that include...

118. The method according to claim 117, wherein the logical condition comprises one or a combination of event conditions.

119. The method according to claim 118, wherein one or a combination of the aforementioned event conditions comprises one or more threshold event numbers.

120. The method according to claim 118, wherein one or a combination of the aforementioned event conditions comprises a threshold event rate.

121. The method according to claim 118, wherein one or a combination of the aforementioned event conditions comprises the absence of an event after a certain time period.

122. The method according to claim 118, wherein one or a combination of the aforementioned event conditions comprises measurements in multiple detectors or regions of detectors.

123. The method according to claim 122, wherein one or a combination of the event conditions comprises a plurality of threshold event conditions, and each of the measured values ​​in a plurality of detectors or regions of detectors comprises a threshold condition associated with the plurality of threshold conditions.

124. The method according to claim 122, wherein one or a combination of the aforementioned event conditions comprises a comparison of measured values ​​between the plurality of detectors or regions of the detectors.

125. The method according to claim 118, wherein one or a combination of the aforementioned event conditions varies with the position on the sample.

126. The method according to claim 118, wherein one or a combination of event conditions comprises an event or a measurement of an event.

127. The method according to claim 118, wherein one or a combination of event conditions comprises a mutual information threshold.

128. The method according to claim 118, wherein one or a combination of the aforementioned event conditions comprises an experimental signal.

129. The method according to claim 128, wherein the experimental signal is used to induce the modulation in (c).

130. The method according to claim 129, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 20 nanoseconds.

131. The method according to claim 129, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 50 nanoseconds.

132. The method according to claim 129, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 100 nanoseconds.

133. The method according to claim 128, wherein the experimental signal comprises a user-defined input.

134. The method according to claim 133, wherein the user-defined input comprises a probe pulse or a pump pulse.

135. (c) The method according to claim 117, further comprising the step of moving the electron source or the ion source to another location on the sample.

136. (c) The method according to claim 117, further comprising the step of turning off the electron source or the ion source.

137. (c) The method according to claim 117, further comprising the step of deflecting the path of the electron source or the ion source.

138. (c) The method of claim 117, which is carried out substantially in real time.

139. (c) The method according to claim 117, which is performed within the electronic counting interval of the detector.

140. (c) The method according to claim 117, further comprising the step of modulating an electron dose waveform or an ion dose waveform based at least in part on one or more measurements.

141. The method according to claim 140, wherein the electron dose waveform or ion dose waveform comprises a continuously variable time profile.

142. The method according to claim 141, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

143. The method according to claim 142, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

144. The method according to claim 142, further comprising the step of receiving an indication of the arbitrarily defined time profile from a user.

145. The method according to claim 140, wherein the electron dose waveform or ion dose waveform comprises a series of intermediate points.

146. The method according to claim 145, wherein the series of intermediate points can be selected individually or collectively to construct the arbitrarily defined time profile.

147. The method according to claim 145, wherein the series of intermediate points comprises more than 1,000 intermediate points.

148. The method according to claim 117, further comprising the step of recording the time it takes for the logical condition to be met in a pixel, element, or portion of the detector.

149. The method according to claim 117, further comprising the step of collecting determinations of whether the aforementioned logical conditions are met, wherein the electronic signal or ion signal or the electron-induced signal or ion-induced signal is from or through the sample.

150. A device, wherein the device is A deflector positioned between an electron source or ion source and a sample area, wherein the deflector modulates the intensity of the electron source or ion source directed towards the sample area according to an electron dose waveform or ion dose waveform having a continuously variable time profile. A detector configured to receive an electronic signal or an electronically induced signal related to the sample area, A controller operably coupled to the deflector and the detector, wherein the controller is configured to determine the continuous variable time profile in response to the electronic signal or electronically induced signal, at least in part on logical conditions. A device equipped with the following features.

151. The device according to claim 150, wherein the logical condition comprises one or a combination of event conditions.

152. The device according to claim 151, wherein one or a combination of the aforementioned event conditions comprises one or more threshold event numbers.

153. The device according to claim 151, wherein one or a combination of the aforementioned event conditions comprises a threshold event rate.

154. The device according to claim 151, wherein one or a combination of the aforementioned event conditions comprises the absence of an event after a certain time period.

155. The device according to claim 151, wherein one or a combination of the aforementioned event conditions comprises measurements in multiple detectors or regions of detectors.

156. The device according to claim 155, wherein one or a combination of the event conditions comprises a plurality of threshold event conditions, and each of the measured values ​​comprises a threshold condition associated with the plurality of threshold conditions.

157. The device according to claim 155, wherein one or a combination of the aforementioned event conditions comprises comparing measurements between the plurality of detectors or regions of the detectors.

158. The device according to claim 151, wherein one or a combination of the aforementioned event conditions varies with the position on the sample.

159. The device according to claim 151, wherein one or a combination of event conditions comprises an event or a measurement of an event.

160. The device according to claim 151, wherein one or a combination of the aforementioned event conditions is provided with an experimental signal.

161. The experimental signal is used to induce the modulation in (c) of the device according to claim 160.

162. The device according to claim 161, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 20 nanoseconds.

163. The device according to claim 161, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 50 nanoseconds.

164. The device according to claim 161, wherein the modulation is induced with a waiting time relative to the pixel residence time of less than 100 nanoseconds.

165. The device according to claim 160, wherein the experimental signal is provided with a user-defined input.

166. The device according to claim 165, wherein the user-defined input comprises a probe pulse or a pump pulse.

167. The device according to claim 150, wherein the controller comprises one or more field-programmable gate arrays.

168. The device according to claim 167, comprising a first field-programmable gate array configured to control the deflector.

169. The device according to claim 167, comprising a first field-programmable gate array configured to control the detector.

170. The device according to claim 150, further comprising an event signal processor configured to receive an electronic signal or an electronically induced signal from a detector and, in response, determine whether a logical condition is met.

171. The device according to claim 170, wherein the event signal processor is part of the controller.

172. The device according to claim 170, wherein the event signal processor is separate from the controller.

173. The event signal processor is the device according to claim 170, wherein it has a single event resolution.

174. The device according to claim 170, wherein the event signal processor comprises an output signal, the output signal being operably coupled to the controller for determining the continuous variable time profile.

175. The device according to claim 174, wherein the output signal is an instantaneous trigger signal.

176. The device according to claim 150, wherein the continuous variable time profile is modulated in real time.

177. The device according to claim 150, wherein the continuous variable time profile is modulated within the electronic counting interval of the detector.

178. The device according to claim 150, wherein the detector comprises a plurality of detectors or detector segments.

179. The device according to claim 150, wherein the detector comprises an image sensor.

180. The device according to claim 150, wherein the detector comprises a single-channel detector.

181. The device according to claim 150, wherein the detector is a multi-channel detector.

182. The device according to claim 150, wherein the device is configured to detect in parallel from a plurality of channels.

183. The device according to claim 150, wherein the waveform comprises a series of intermediate points.

184. The device according to claim 183, wherein the series comprises more than 1,000 intermediate points.

185. The device according to claim 150, wherein the electron dose waveform or ion dose waveform comprises an arbitrarily defined time profile.

186. The device according to claim 185, wherein the waveform comprises a series of intermediate points, the series of intermediate points being individually or collectively selectable to construct the arbitrarily defined time profile.

187. The device according to claim 185, wherein the arbitrarily defined time profile has a time resolution of less than 10 nanoseconds (ns).

188. The device according to claim 185, wherein the arbitrarily defined time profile is indicated by the user.

189. The deflector device according to claim 150, comprising a driving electrode and an electrode for a fixed voltage.

190. The device according to claim 150, wherein the deflector comprises two drive electrodes.

191. The device according to claim 150, wherein the electron dose waveform or ion dose waveform modulates the average intensity of the electron source or ion source directed toward the sample area.

192. The device according to claim 191, wherein the average intensity is modulated without substantially altering other image conditions.

193. The device according to claim 191, wherein the average intensity is controllable independently of the driving voltage of the electron source or the ion source.

194. The device according to claim 191, wherein the average intensity is continuously variable over a range of 0 to 100% dose transmission.

195. The device according to claim 150, wherein the electron dose waveform or ion dose waveform comprises a periodic waveform.

196. The device according to claim 150, wherein the electron dose waveform or ion dose waveform is non-periodic.

197. The device according to claim 150, wherein the electron dose waveform or ion dose waveform comprises a pump pulse and a probe pulse.

198. The device according to claim 150, wherein the electron dose waveform or ion dose waveform is a square wave.

199. The device according to claim 198, wherein the transition time between high voltage and low voltage is less than approximately 50 nanoseconds (ns) and is defined as the sum of ringing time and slope time.

200. The device according to claim 198, wherein the transition time between high voltage and low voltage is less than about 10 nanoseconds (ns) and is defined as the slope time of the transition voltage from about 10% to about 90%.

201. The device according to claim 198, wherein the pulse width of the square wave is aperiodic.

202. The device according to claim 150, wherein the electron or ion dose waveform has a minimum exposure time of about 100 nanoseconds (ns).

203. A pattern generator configured to produce an electrical signal representing the electron dose waveform or ion dose waveform, A driver electronic device configured to receive the electrical signal from the pattern generator and to supply a voltage having the electron dose waveform or ion dose waveform to the deflector, The device according to claim 150, further comprising the above.

204. The method further comprises one or more computer processors equipped with instructions, wherein when an instruction is executed, Receiving indication of the aforementioned electron dose waveform or ion dose waveform, To deliver the indication to the pattern generator The device according to claim 107, configured to perform the following:

205. A non-transient computing device-readable medium, the non-transient computing device-readable medium stores instructions that can be executed by a processor to cause a computing device to perform a method, and the method is (a) A step of receiving a condition code, (b) The step of receiving a signal corresponding to an electronic signal or an electron-induced signal from a sample, (c) A step of comparing the received signal with the condition code, (d) A step of determining whether an output signal should be transmitted based at least in part on the comparison performed in (c) and Non-transient computing device-readable media, including [specific examples of non-transient computing devices].

206. The non-transient computing device-readable medium according to claim 205, wherein the condition code comprises a reference to a lookup table describing a set of logical conditions.

207. The condition code comprises a set of logical conditions, as described in claim 205, for a non-transient computing device-readable medium.

208. The non-transient computing device-readable medium according to claim 206 or claim 207, wherein the logical condition comprises one or a combination of event conditions.

209. The non-transient computing device readable medium according to claim 206 or claim 207, wherein one or a combination of the event conditions comprises one or more threshold event numbers.

210. A non-transient computing device readable medium according to claim 206 or claim 207, wherein one or a combination of the aforementioned event conditions comprises a threshold event rate.

211. A non-transient computing device-readable medium according to claim 206 or 207, wherein one or a combination of the aforementioned event conditions comprises the absence of an event after a certain time period.

212. The non-transient computing device readable medium according to claim 206 or claim 207, wherein one or a combination of the aforementioned event conditions comprises measurements in a plurality of detectors or regions of detectors.

213. Non-transient computing device readable medium according to claim 212, wherein one or a combination of the event conditions comprises a plurality of threshold event conditions, and each of the measured values ​​comprises a threshold condition associated with the plurality of threshold conditions.

214. The non-transient computing device readable medium according to claim 212, wherein one or a combination of the aforementioned event conditions comprises a comparison of measurements between the plurality of detectors or regions of the detectors.

215. A non-transient computing device-readable medium according to claim 206 or 207, wherein one or a combination of the aforementioned event conditions varies with the position on the sample.

216. A non-transient computing device-readable medium according to claim 206 or claim 207, wherein one or a combination of event conditions comprises an event or a measurement of an event.

217. The output signal comprises a trigger signal, as described in claim 205, for a non-transient computing device readable medium.

218. The non-transient computing device readable medium according to claim 217, wherein the trigger signal comprises a latency of less than 20 nanoseconds relative to the pixel dwell time.

219. The modulation is induced with a latency of less than 50 nanoseconds relative to the pixel residence time, as described in claim 217.

220. The modulation is induced with a latency of less than 100 nanoseconds relative to the pixel residence time, as described in claim 217.

221. The method according to claim 43, wherein the information threshold comprises a mutual information threshold.

222. The method according to claim 110, wherein the information threshold comprises a mutual information threshold.

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