Arbitrary electron dose waveforms for electron microscopy

Abstract

The device may include an electron source, a detector, and a deflector. The electron source may be directed toward the sample area. The detector may receive an electron signal or an electron-induced signal. The deflector may be positioned between the electron source and the sample. The deflector may modulate the intensity of the electron source directed toward the sample area according to an electron dose waveform having a continuously variable time profile. The disclosed systems and methods allow the functional form and time scale of the dose (e.g., electron dose waveform) to be adjusted to the dynamics of the sample in a fast, precise, and repeatable manner. The methods and systems disclosed herein may be used to reduce or control the effects of the electron dose during transmission electron microscopy (TEM) measurements.

Description

[Background technology]

[0001] (cross reference) This application claims the benefit of U.S. Provisional Application No. 63 / 176,115, filed April 16, 2021, which is incorporated by reference herein for all purposes.

[0002] (Statement regarding federally funded research) This invention was made with United States Government support under Award No. DE-SC0013104 awarded by the United States Department of Energy.

[0003] Electron microscopes may include various systems and methods for delivering an electron dose. For example, in transmission electron microscopy, high-energy electrons may pass through a sample from above and form an image on a detector below. This process, which is intended to measure properties of the sample, may alter or even damage the sample. Summary of the Invention [Means for solving the problem]

[0004] Applicant recognizes that there exists an unmet need for new methods and systems for temporally modulating the electron dose on a transmission electron microscope. The disclosed systems and methods allow the dose function shape and time scale (e.g., electron dose waveform) to be adjusted to the dynamics of the sample in a fast, precise, and repeatable manner. The methods and systems disclosed herein may be used to reduce or control the effects of the electron dose during transmission electron microscopy (TEM) measurements.

[0005] The systems and methods disclosed herein may improve upon methods of adjusting electron dose, which operate, for example, by modulating the electron optical settings of the electron beam. Such settings may include beam current, convergence angle, and aperture size. Adjusting the electron optical settings may not allow the electron dose to be modulated on fast time scales. Furthermore, matching the electron optics for transmission electron microscopy to achieve atomic resolution may be complex and may involve adjusting multiple interconnected parameters within the electron optical system.

[0006] The systems and methods disclosed herein provide the following non-limiting advantages: allowing the average dose to be adjusted on a fast time scale; allowing the average dose to perform an arbitrary function of time; allowing the average dose (e.g., duty cycle) to be continuously varied across a range of 0-100% dose penetration; allowing the dose waveform to be synchronized to changes in the detector, the stimulus to the sample, or the electron-optical conditions of the microscope; the dose waveform may take into account one or more of the following: information about the sample, the deflection electronics, the detectors involved in the measurement, and a determined waveform that is input by the user into the control software. This may provide at least some of the following: allowing the time profile of the pump pulse, the probe pulse, or both to be customized in a pump-probe experiment; reducing limitations on the dose waveform generated by the physical constraints of ultrafast pulsed electron sources such as laser-driven cathodes and radio frequency pulsers, e.g., limited dynamic range and / or duration for the waveform; allowing the dose waveform to be applied at selectable accelerating voltages available for the electron beam; and allowing the pulses that make up the dose waveform to occur at non-uniform repetition rates.

[0007] In one aspect, the disclosure provides a device that may include an electron source directed towards a sample area, a detector for receiving an electron signal or an electron induced signal, and a deflector positioned between the electron source and the sample, the deflector modulating an intensity of the electron source directed towards the sample area according to an electron dose waveform having a continuously variable temporal profile.

[0008] In another aspect, the disclosure provides a device that may include an electron source directed toward a sample area, a detector for receiving an electron signal or an electron induced signal, and a deflector positioned between the electron source and the sample, the deflector modulating an intensity of the electron source directed toward the sample area according to an electron dose waveform having a variable temporal profile, the variable temporal profile comprising a selectable irregular pulse width, a selectable irregular repetition rate, or both.

[0009] In some embodiments, the electron beam waveform comprises an arbitrarily defined time profile. In some embodiments, the waveform comprises a series of waypoints. In some embodiments, the series of waypoints are individually or collectively selectable to construct the arbitrarily defined time profile. In some embodiments, the series comprises more than 1,000 waypoints. In some embodiments, the arbitrarily defined time profile comprises a time resolution of less than 10 nanoseconds. In some embodiments, the arbitrarily defined time profile is indicated by a user.

[0010] 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 dose waveform modulates the average intensity of the electron source directed towards the sample area. In some embodiments, the average intensity is modulated substantially without change in other image conditions. In some embodiments, the device comprises a physical or virtual knob to adjust the average intensity. In some embodiments, the average intensity is controllable independently from the drive voltage of the electron source. In some embodiments, the average intensity is continuously variable across a range of 0-100% dose transmission.

[0011] In some embodiments, the electron beam waveform comprises a periodic waveform. In some embodiments, the electron beam waveform is non-periodic. In some embodiments, the electron beam waveform comprises a pump pulse and a probe pulse. In some embodiments, the electron beam waveform is a square wave. In some embodiments, the transition time between the high and low voltages is less than about 50 nanoseconds, defined as the sum of the ringing time plus the slope time. In some embodiments, the transition time between the high and low voltages is less than about 10 nanoseconds, defined as the slope time of about 10% to about 90% of the transition voltage. In some embodiments, the pulse width of the square wave is non-periodic. In some embodiments, the electron beam waveform comprises a minimum exposure time of about 100 nanoseconds.

[0012] In some embodiments, the device comprises a pattern generator configured to generate an electrical signal representing an electron beam waveform, and driver electronics configured to receive the electrical signal from the pattern generator and provide a voltage to the deflector that comprises the electron beam waveform. In some embodiments, the device comprises one or more computer processors comprising instructions that, when executed, are configured to receive an indication of the electron beam waveform and deliver the indication to the pattern generator.

[0013] In some embodiments, the one or more computer processors comprise instructions for adjusting the shape of the electron beam waveform according to one or more parameters. In some embodiments, the one or more parameters comprise information about one or more of a property of the image from the detector, a property of the deflector, a property of the driver electronics, a property of the detector, and an indication of the electron beam waveform. In some embodiments, the one or more parameters comprise an indication of a minimum, maximum, or fixed value for a pulse width or pulse repetition rate of the electron beam waveform.

[0014] In some embodiments, the one or more parameters comprise timing constraints of a deflector, driver electronics, or pattern generator. In some embodiments, the one or more parameters comprise a characteristic time scale of a sample or a process within the sample. In some embodiments, the one or more parameters comprise a time-dependent voltage bias or temperature. In some embodiments, the one or more parameters comprise a detector dose rate or timing considerations. In some embodiments, the one or more parameters comprise an indication of data signal quality from collected or real-time measurements. In some embodiments, the one or more parameters comprise an indication of the effect of the intensity of an electron beam waveform on a sample from collected or real-time measurements.

[0015] In some embodiments, the one or more processors comprise instructions for adjusting the timing of the electron dose waveform to changes in the collection time of the detector, the location of one or more sub-portions of the detector, the arrival time of the stimulus to the sample area, or the electronic optical conditions of the device. In some embodiments, the pattern generator is an analog or digital pattern generator. In some embodiments, the pattern generator comprises an analog to digital converter.

[0016] In another aspect, the present disclosure provides a method for modulating a dose in a transmission electron microscope image, which may include providing an electron source directed toward a sample area, receiving an electron dose waveform at a deflector disposed between the electron source and the sample area, the electron dose waveform modulating an intensity of the electron source directed to the sample area in accordance with the electron dose waveform, and outputting an electron signal or an electron induced signal related to at least a portion of the modulated intensity.

[0017] In some embodiments, the electron beam waveform comprises a continuously time-varying profile. In some embodiments, the electron beam waveform comprises an arbitrarily defined time profile. In some embodiments, the waveform comprises a series of waypoints. In some embodiments, the series of waypoints are individually or collectively selectable to construct the arbitrarily defined time profile. In some embodiments, the series comprises more than 1,000 waypoints. In some embodiments, the arbitrarily defined time profile comprises a time resolution of less than 10 nanoseconds. In some embodiments, the method includes receiving an indication of the arbitrarily defined time profile from a user. In some embodiments, the method further includes providing a device of any aspect or embodiment.

[0018] In another aspect, the present disclosure provides a computer-implemented method for modulating an electron dose on a transmission electron microscope (TEM), which may include (a) receiving, at a processor, an indication of an electron dose waveform comprising a representation of a time profile of an intensity of an electron dose directed to a sample area in the TEM, (b) transmitting the indication to the TEM, where an electrical signal representing the indication drives a deflector in the TEM, thereby modulating the time profile of the electron dose, (c) receiving one or more adjustable parameters, where the one or more adjustable parameters comprise information about one or more of a property of a TEM image, a property of a deflector, a property of driver electronics in the TEM, a property of a detector in the TEM, and an indication of the electron dose waveform, and (d) updating the indication of the electron dose waveform based on the one or more parameters.

[0019] In some embodiments, the method may include continuously updating the indication of the electron dose waveform. In some embodiments, the method further includes providing the device of any aspect or embodiment.

[0020] Another aspect of the present disclosure provides a system comprising one or more computer processors and a computer memory coupled thereto, the computer memory comprising machine executable code that, upon execution by the one or more computer processors, implements any of the methods described above or elsewhere herein.

[0021] Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in the art from the following detailed description, in which only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modification in various obvious respects, all without departing from the present disclosure. Thus, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

[0022] (Incorporated by reference) All publications, patents, and patent applications mentioned herein are incorporated herein by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated in its entirety by reference. In the event of a conflict between a term in this specification and a term in an incorporated reference, the term in this specification shall control. [Brief description of the drawings]

[0023] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings.

[0024] [Figure 1] FIG. 1 shows a non-limiting example of a device including a deflector for delivering an electron beam waveform, according to an embodiment.

[0025] [Diagram 2] FIG. 2 shows an example of a deflector, according to an embodiment.

[0026] [Diagram 3] FIG. 3 shows a schematic diagram of a computer-implemented method for modulating dose in a transmission electron microscope image, according to an embodiment.

[0027] [Figure 4] FIG. 4 shows a schematic diagram of a method for modulating dose in an electron microscope image, according to an embodiment.

[0028] [Diagram 5] FIG. 5 shows an example of a high-resolution TEM image taken with dose decay using a deflector-modulated electron dose waveform.

[0029] [Figure 6] FIG. 6 shows a schematic diagram of a high-resolution electron microscopy experiment using a deflector-modulated electron dose waveform.

[0030] [Figure 7] FIG. 7 illustrates one example of a computer system that can be used to implement the electron dose modulation method of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Detailed Description For example, methods and systems for modulating electron dose for use in transmission electron microscopy (TEM) are described. The systems and methods of the present disclosure allow the functional form and time scale of the dose to be adjusted to the dynamics of the sample in a precise and repeatable manner. In some cases, this may be used to reduce or control the effects of the electron dose during TEM measurements.

[0032] In some cases, the effect of the electron dose on the sample can be detrimental. For example, the dose can deform and move the sample, or cause the sample to accumulate heat or net charge, each of which can lead to a blurred image. In some cases, the structure of the sample can be altered, so that the original structure of interest is no longer visible. In some cases, the effect of the electron dose on the sample can occur at the beginning of the exposure. For example, the sample can jump or otherwise result in a blurred image for a while. In some cases, these effects can appear for a limited time after the electron beam touches them. In some cases, these effects can be reduced or disappear at later points in the exposure. In some cases, the effect of the dose at the beginning of the sample collection can be detrimental because the sample may have less damage than can accumulate over the course of the measurement. In some cases, the effect of the dose can reduce the quality of the data. Without being limited by theory, this can be due to, for example, transient charging and / or sample motion. In some cases, the effect of dose on a sample can be mitigated by slowly varying the electron dose with time. For example, varying the dose with time can give the sample an opportunity to adjust as the dose increases or decreases. For example, the effect of dose can be mitigated by controlling the duration of short repeated exposures.

[0033] In some cases, it may be of interest to study electron dose induced kinetics. For example, the nucleation and growth of nanoparticles may be induced by high intensity bursts of an electron beam and subsequently measured at reduced intensity. By controlling the dose rate at each stage of the process, the rate of the process under study may be tuned across the bandwidth of the detector.

[0034] The present disclosure provides systems and devices comprising an electron source directed toward a sample area, a detector for receiving an electron signal or an electron-induced signal, and a deflector positioned between the electron source and the sample. The deflector may modulate the intensity of the electron source directed to the sample area according to an electron dose waveform. The waveform may have a continuously variable temporal profile. For example, the waveform may have a temporal profile with one or more of a non-uniform repetition rate, a non-uniform pulse width, or a non-uniform pulse shape. The deflector may apply an electric field to the electron source (e.g., an electron beam) directed to the sample area.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0036] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Any reference to "or" herein is intended to include "and / or" unless stated otherwise.

[0037] As used herein, unless otherwise specified, the term "about" or "approximately" refers to an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In some cases, the term "about" or "approximately" refers to within 1, 2, 3, or 4 standard deviations. In some cases, the term "about" or "approximately" refers to 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" a number refers to that number ± 10% of that number. In some cases, the term "about" when used in the context of a range refers to that range of minus 10% of its lowest value and plus 10% of its highest value.

[0038] As described above, methods and systems for modulating electron dose for use in, for example, transmission electron microscopy (TEM) imaging are described. The methods and systems of the present disclosure may improve upon the method of modulating electron dose by adjusting electron optical settings such as beam current, convergence angle, and aperture size. In such a method, the dose cannot be varied quickly in time, the method may require skill, and many parameters of the system may vary with intensity, which may reduce the quality of the image.

[0039] In another embodiment, the disclosed method and system may improve upon the method of modulating the electron dose by turning the beam completely on or off using shutters and / or blankers that are not capable of operating at high frequencies, such as kilohertz (kHz) or higher. For example, the beam may be turned off while the sample is not being measured. In such an embodiment, the dose rate may be fixed at two values ​​(on and off).

[0040] In another example, the disclosed method and system may improve upon a method in which the electron beam is turned off during some portions of a scanning probe measurement, and thus the sample is sparsely measured. In a sparse measurement technique, the dose rate cannot be adjusted uniformly across the entire sample, and therefore the effects of high dose cannot be fully controlled at all locations on the sample. Specialized computer algorithms are used to estimate the outcome of a complete measurement, thereby potentially increasing the difficulty of the sparse measurement technique. In some cases, the algorithm may miss details that would be present in a complete measurement. In some cases, the algorithm may produce details that would not be present in a complete measurement. In a sparse measurement technique, the dose to the entire measurement area of ​​the sample cannot be varied quickly over time.

[0041] In another embodiment, the disclosed method and system may improve the method of modulating the electron dose by a radio frequency pulser, including a cavity or stripline-based resonator. For example, a resonant radio frequency pulser may split the beam into a uniform train of identical pulses on a gigahertz (GHz) time scale. In such an embodiment, the pulse train may be limited to a specific repetition rate and a low, quasi-fixed duty cycle. In such an embodiment, the resonant pulser may not implement an arbitrary waveform. In some cases, the resonant pulser may be specifically arranged for a fixed acceleration voltage on a transmission electron microscope that can operate at various voltages. In such cases, pulsing operation may not be available for all possible optical settings on the transmission electron microscope.

[0042] In a somewhat related technique, laser-driven cathode illumination and / or photoemission may be used to modulate the dose. A transmission electron microscope may be configured such that electrons are emitted when laser light strikes the cathode. A pulsed or modulated electron beam may be generated by using a pulsed laser for this purpose. Due to the physical constraints of the laser and cathode, the method may have a limited tuning range. Thus, it cannot perform arbitrary waveforms in the same sense as the systems and methods of the present disclosure. The photoemission method may also be much more technically challenging and expensive compared to the systems and methods of the present disclosure, and may have deleterious effects on image quality, maximum beam current, or TEM component life. For example, a laser-driven photocathode may adjust the continuous current by adjusting the power output of a continuous wave (CW) laser (e.g., 1% to 100% power level adjustment). In some examples, a laser-driven photocathode may not change any measurement parameters on the TEM other than the photoelectron current.

[0043] 1 shows a non-limiting example of a device comprising a deflector for delivering an electron dose waveform, according to an embodiment. In some cases, the device is a TEM with a high-speed electrostatic deflector in which an electron beam emanating from an electron gun or other source positioned above the instrument propagates downward through a sample.

[0044] Provided herein is a device comprising an electron source 102 directed towards a sample area 110, a detector 104 for receiving electron signals or electron-induced signals, and a deflector 106 positioned between the electron source and the sample. In some cases, the device is a transmission electron microscope, however, deflector systems such as those disclosed herein may also be used in conjunction with other electron microscopy and electron spectroscopy applications such as serial section electron microscopy (ssEM), scanning electron microscopy (SEM), reflection electron microscopy (REM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), etc. There are instruments capable of more than one of these modes of operation. There are variations in geometry such that the electron source can be on the bottom or side of the instrument and the beam can travel upwards or horizontally.

[0045] As shown in FIG. 1, an electron source 102 may be provided. 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 comprise an electron gun. The electron source may comprise a hot filament source that emits electrons. The electron source may comprise a field emission source that emits electrons. The electron source may comprise one or more acceleration optics. For example, the acceleration optics may comprise a cathode and an anode. The anode may comprise a controllable electrode voltage for accelerating the electrons away from the filament at a selectable voltage. The electron source may comprise a set of electron optics for shaping the spatial profile of the electron source. For example, the electron source may comprise one or more electrostatic or electrokinetic lenses. In some cases, the electron source may be directed towards the sample by one or more steering deflectors. The steering deflectors may or may not also be used to control the temporal profile of the electron dose waveform arriving at the sample area.

[0046] As shown in FIG. 1, a detector 104 may be provided. The detector may receive electron signals propagated through the sample area or electron-induced signals from the sample area. The detector may be a two-dimensional detector array. The two-dimensional detector array may in some cases comprise 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 may refer to a two-dimensional array of individual detectors, e.g., a CCD or CMOS image sensor. In some cases, the two-dimensional detector array may comprise a two-dimensional array of individual detectors, including a CMOS image sensor, a CCD image sensor, a dark-field STEM detector, a Faraday cup sensor, or a combination of other types of detectors. In some cases, the detector may comprise an energy dispersive X-ray spectrometer (EDS) or an energy dispersive X-ray (EDS) detector. An EDS detector may measure electron-induced signals. For example, an EDS detector may measure X-rays that are backscattered as an electron beam strikes the sample area. In some cases, x-rays can be generated when an electron beam collides and interacts with a sample as it passes through the sample area.

[0047] 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 that include a layer that emits photons when struck by electrons, complementary metal-oxide semiconductor (CMOS) image sensors and cameras that include a layer that emits photons when struck by electrons, electron direct 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.

[0048] As shown in FIG. 1, a deflector 106 may be provided. The deflector may be positioned between the electron source and the sample. The deflector may comprise an embodiment, variation, or implementation of the deflector described herein with respect to FIG. 2. The systems and methods of the present disclosure may use a high-speed electrostatic deflector. The high-speed electrostatic deflector may be placed after the source of the electron beam in the TEM. In some examples, when no voltage is applied, the electron beam may transmit 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 they do not reach the sample. In this way, the beam may be turned on and off quickly. In some cases, the beam may propagate through the aperture 108. The voltage applied to the deflector may control whether the electron beam propagates through the aperture or is blocked by the aperture.

[0049] The deflector 106 may modulate the intensity of the electron source directed to the sample area. The modulation may be accomplished through one or a combination of the following: pulse width modulation (PWM), pulse density modulation (PDM), or delta modulation (DM). The modulation of the electron source by the deflector may be associated with an electron dose waveform. The waveform provided may modulate the amount of electrons (e.g., dose) arriving at the sample area. In some cases, the waveform may determine the time profile of the average dose in the sample area. In some examples, a waveform that determines the time profile of the average dose may be provided. The time profile of the average dose may be indicated by a user. The indicated time profile may be converted into a waveform. The conversion into a waveform may be performed or assisted by a processor with instructions as 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 high-speed electrostatic deflector.

[0050] Without being limited by theory, PDM and / or DM modulation schemes may balance the goal of minimizing the number of on-off transitions with the goal of producing a smooth time-varying intensity. On-off transitions may be disadvantageous in at least some cases; first, they may consume power, which may limit the maximum time resolution of the dose waveform, and second, intermediate states between the transitions between on and off may reduce data quality. PDM and / or DM systems may inherently exploit non-uniform pulse durations. For example, in a PDM scheme, the density of pulses over time may be varied according to a criterion function, such as, for example, a periodic function. For example, in a DM scheme, the pulse duration over time may be varied according to a criterion function, such as, for example, a periodic function.

[0051] The electron dose waveform may have an arbitrarily defined time profile. The arbitrarily defined electron dose profile may be a profile that is not dictated by a regular periodic function. The regular periodic function may include a pulse pattern or a regular pulse pattern, such as a square wave, a sinusoid, 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 forearm function. The arbitrarily defined electron dose waveform may be an electron dose waveform that does not have a regular pulse width or that does not have a regular repetition rate, or that does not have both. The arbitrarily defined electron dose waveform may be an electron dose waveform that has a selectable irregular pulse width or that has a selectable irregular repetition rate, or that has both.

[0052] In some cases, the arbitrarily defined electron dose profile may comprise a dose profile with a series of points (e.g., waypoints). The waveform may be interpolated from the series of points. The series of waypoints can be individually or collectively selected to construct the arbitrarily defined time profile. In some cases, the arbitrarily defined time profile is indicated by a user. In some cases, the user may provide a function and a series of waypoints may be generated. In some cases, the user may move the waypoints or a set of waypoints individually to vary the waveform. In some cases, the electron dose waveform is non-periodic.

[0053] In some cases, the time profile comprises a time resolution. In some cases, the time resolution is defined as the distance between waypoints 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. The time resolution may optionally be less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, less than about 1 nanosecond, less than about 500 picoseconds (ps), less than about 250 picoseconds, less than about 100 picoseconds, less than about 50 picoseconds, less than about 20 picoseconds, less than about 10 picoseconds, or less. Any of the lower and upper limits described in this paragraph may be combined to form a range included within the present disclosure, for example, the time resolution may be within 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.

[0054] In some cases, the series of waypoints comprises more than about 1,000 waypoints. In some cases, the series of waypoints comprises more than about 10,000 waypoints. In some cases, the series of waypoints comprises more than about 100,000 waypoints. In some cases, the series of waypoints comprises more than about 1,000,000 waypoints or more. In some cases, the series of waypoints comprises between about 10,000 waypoints and about 1,000,000 waypoints. In some cases, the series of waypoints is repeated several times to form a series. In some cases, the series is repeated about 10 times, about 100 times, about 1,000 times, about 10,000 times, about 100,000 times, about 1,000,000 times, about 1,000,000 times, or more than that. Any of the lower and upper limits set forth in this paragraph may be combined to form ranges included within the disclosure, e.g., the number of repeats in a time series may be within the range of about 10 to about 10,000, about 1 to about 100, or about 1 to about 1,000.

[0055] In some cases, the waveform may comprise multiple pulses in a sequence. For example, an electron beam waveform may comprise a pump pulse and a probe pulse. Pump-probe experiments may be used to measure time-dependent processes in a sample. In some cases, the pump pulse and the probe pulse may have the same shape, e.g., two Gaussians, two Lorentzians, 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. The series of pulses may be repeated several times to form a series. In some cases, the series is repeated about 10 times, about 100 times, about 1,000 times, about 10,000 times, about 100,000 times, about 1,000,000 times, or more. Any of the lower and upper limits set forth in this paragraph may be combined to form ranges included within the disclosure, e.g., the number of repeats in a time series may be within the range of about 10 to about 10,000, about 1 to about 100, or about 1 to about 1,000.

[0056] In some cases, the repetition rate of the series of electron beam waveforms is greater than about 1 kHz, greater than about 5 kHz, greater than about 10 kHz, greater than about 20 kHz, greater than about 50 kHz, greater than about 100 kHz, or greater. In some cases, the repetition rate of the series of electron beam waveforms is less than about 1,000 MHz, less than about 500 MHz, less than about 200 MHz, less than about 100 MHz, or less. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, for example, the repetition rate of the series of electron beam waveforms may be between about 500 kHz and about 1 MHz, between about 100 kHz and about 10 MHz, or between about 10 kHz and about 100 MHz.

[0057] In some cases, the minimum repetition period of the series of electron beam waveforms may optionally be less than about 100 milliseconds (ms), less than about 50 ms, less than about 20 ms, less than about 10 ms, less than about 5 ms, less than about 1 microsecond (µs), less than about 500 µs, less than about 250 µs, less than about 100 µs, less than about 50 µs, less than about 20 µs, less than about 10 µs, or less. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, for example, the minimum repetition period may be within the range of about 1 ms to about 1 µs, about 100 µs to about 1 µs, or about 20 ns to about 1 µs.

[0058] The electron beam waveform may have a continuously variable time profile. For example, a user may determine the waveform and later modify the waveform. Modifications may include changing the location of one or more waypoints, changing the time between repetitions of a series of waveforms, changing the number of repetitions, etc. In some cases, the width of the pulses of the square wave may be dynamically changed. For example, the pulse width of the series of square waves may be aperiodic or have a continuously adjustable periodicity.

[0059] 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, a sine wave, or a TTL pulse, which may include a regularly repeating pulse to the deflector, a ramp pulse, a Gaussian, a Laurentian, an exponential rise, an exponential decay, and a haversine function. In some cases, the electron dose waveform is periodic.

[0060] In some cases, the transition between the high and low deflector voltages may be characterized by a transition time. For example, the transition time between the high and low voltages is less than about 50 nanoseconds, defined as the sum of the ringing time and the slope time. In some cases, the transition time between the high and low voltages is less than about 1 microsecond, less than about 500 nanoseconds, less than about 250 nanoseconds, less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, or less.

[0061] In some cases, the transition between the high and low deflector voltages may be characterized by a transition time. For example, the transition time between the high and low voltages is less than about 10 nanoseconds, defined as the slope time of about 10% to about 90% of the transition voltage. In some cases, the transition time between the high and low voltages is less than about 1 microsecond, less than about 500 nanoseconds, less than about 250 nanoseconds, less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, less than about 2 nanoseconds, less than about 1 nanosecond, or less.

[0062] In some cases, the electron beam waveform is characterized by a minimum exposure time. For example, the electron beam waveform may comprise a minimum exposure time of about 100 nanoseconds. In some cases, the minimum exposure time is less than about 1 microsecond, less than about 500 nanoseconds, less than about 250 nanoseconds, less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, less than about 2 nanoseconds, less than about 1 nanosecond, or less. Any of the lower and upper limits described in this paragraph may be combined to form a range included within the present disclosure, for example, the minimum exposure time may be within 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.

[0063] In some cases, the temporal profile comprises 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 temporal resolution may be less than about 10 nanoseconds. The minimum pulse width may optionally be less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, less than about 1 nanosecond, less than about 500 picoseconds (ps), less than about 250 picoseconds, less than about 100 picoseconds, less than about 50 picoseconds, less than about 20 picoseconds, less than about 10 picoseconds, or less. Any of the lower and upper limits described in this paragraph may be combined to form a range included within the present 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.

[0064] In some cases, the temporal profile comprises a 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 ns. The temporal resolution may be less than about 50 ns. The fastest pulse duration may optionally be less than about 100 ns, less than about 50 ns, less than about 20 ns, less than about 10 ns, less than about 5 ns, less than about 1 ns, less than about 500 picoseconds (ps), less than about 250 ps, ​​less than about 100 ps, ​​less than about 50 ps, ​​less than about 20 ps, ​​less than about 10 ps, ​​or less. Any of the lower and upper limits described in this paragraph may be combined to form a range included within the disclosure, for example, the fastest pulse duration may be within the range of about 100 ns to about 5 ns, about 50 ns to about 1 ns, or about 20 ns to about 1 ns.

[0065] In some examples, dose modulation may be implemented using a fast electrostatic shutter. The electron beam may be rapidly blanked at a fixed repetition rate (kHz-MHz) so that the average dose is reduced. In this example, the peak dose rate may not change. If the average dose rate or repetition frequency is changed, the setting may take effect after a delay. In some cases, the delay may be a non-repeatable delay, a regularly repeatable delay, or an irregularly repeating delay.

[0066] The repetition rate of the electron beam waveform in shutter mode may be in the range of about 500 kHz (kilohertz) to about 1 MHz (megahertz) at an electron beam voltage in the range of about 80 kV (kilovolts) to about 300 kV. The repetition rate may be in the range of about 10 kHz to about 100 MHz at an electron beam voltage in the range of about 80 kV to about 300 kV. The repetition rate may be in the range of about 500 kHz to about 1 MHz at an electron beam voltage in the range of about 0.5 kV to about 1,000 kV.

[0067] In some cases, the repetition rate of the electron beam waveform is greater than about 1 kHz, greater than about 5 kHz, greater than about 10 kHz, greater than about 20 kHz, greater than about 50 kHz, greater than about 100 kHz, or more. In some cases, the repetition rate of the electron beam waveform is less than about 1,000 MHz, less than about 500 MHz, less than about 200 MHz, less than about 100 MHz, or less. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, e.g., from about 500 kHz to about 1 MHz, from about 100 kHz to about 10 MHz, or from about 10 kHz to about 100 MHz.

[0068] As shown in FIG. 1, the device may include drive electronics 120, a digital pattern generator 130, and a sequence generation algorithm 140. The sequence generation algorithm may include an embodiment, variation, or implementation of the deflector described herein with respect to FIG. 3. For example, the pattern generator may generate an electrical signal representing an electron dose waveform. The driver electronics may receive an electrical signal from the pattern generator and provide a voltage comprising the electron dose waveform to the deflector. The sequence generation algorithm may receive an indication of the electron dose waveform to a user and deliver the indication to the pattern generator and generate the electrical signal.

[0069] 2 shows an example of a deflector 106, according to an embodiment. 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 a different direction. In some examples, various pairs of electrodes may move electrons in different axes. In the example shown, the detector has two electrodes X1 and X2, which are shaped like plates.

[0070] In some cases, the deflector comprises a drive electrode and an electrode at a fixed voltage. In some cases, the deflector comprises a drive electrode near a portion of the microscope that is held at a fixed voltage and acts as a second electrode at a fixed voltage. In some cases, the portion 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 within a 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 within the disclosure, for example, the drive voltage may be within 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.

[0071] In some cases, the deflector includes two drive electrodes. For example, the two drive electrodes may have opposite voltages. The two drive electrodes may have equal, opposite 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 within a 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 within the disclosure, for example, the drive voltage may be within 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.

[0072] As shown, the deflector may be part of a beam deflection system. For example, the beam deflection system may comprise drive electronics 120, a digital pattern generator 130, and a sequence generation algorithm 140. The sequence generation algorithm may comprise an embodiment, variation, or implementation of the deflector described herein with respect to FIG. 3. The sequence generation algorithm may provide a digital signal to the digital pattern generator.

[0073] The device may include drive electronics 120. The drive electronics receive electrical signals from a digital pattern generator and output voltages to drive the electrodes of the deflector. The drive electronics may include digital power amplifiers. The digital power amplifiers may mirror the incoming digital pattern at the deflector plates. The drive electronics may facilitate waveform flexibility in PWM modulation schemes. The drive electronics may include analog signal conditioning components, such as low pass filters, high pass filters, DC offsets, grounding, shielding, etc. The drive electronics may include separate channels for driving the electrodes.

[0074] The drive electronics may provide fast transition times. In some cases, the transition between the high and low deflector voltages may be characterized by a transition time. For example, the transition time between the high and low voltages is less than about 50 nanoseconds, defined as the sum of the ringing time plus the slope time. In some cases, the transition time between the high and low voltages is less than about 1 microsecond, less than about 500 nanoseconds, less than about 250 nanoseconds, less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, or less. In some cases, the transition between the high and low deflector voltages may be characterized by a transition time. For example, the transition time between the high and low voltages is less than about 10 nanoseconds, defined as the slope time of about 10% to about 90% of the transition voltage. In some cases, the transition time between the high voltage and the low voltage is less than about 1 microsecond, less than about 500 nanoseconds, less than about 250 nanoseconds, less than about 100 nanoseconds, less than about 50 nanoseconds, less than about 20 nanoseconds, less than about 10 nanoseconds, less than about 5 nanoseconds, less than about 2 nanoseconds, less than about 1 nanosecond, or less.

[0075] The driving electronics may provide a sustained high frequency. For example, the frequency provided by the driving electronics may be in the range of about 500 kHz (kilohertz) to about 1 MHz (megahertz) at an electron beam voltage in the range of about 80 kV to about 300 kV. The frequency provided by the driving electronics may be in the range of about 10 kHz to about 100 MHz at an electron beam voltage in the range of about 80 kV to about 300 kV. The frequency provided by the driving electronics may be in the range of about 500 kHz to about 1 MHz at an electron beam voltage in the range of about 0.5 kV to about 1,000 kV.

[0076] In some cases, the frequency provided by the drive electronics is greater than about 1 kHz, greater than about 5 kHz, greater than about 10 kHz, greater than about 20 kHz, greater than about 50 kHz, greater than about 100 kHz, or greater. In some cases, the frequency provided by the drive electronics is less than about 1,000 MHz, less than about 500 MHz, less than about 200 MHz, less than about 100 MHz, or less. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, such as, for example, from about 500 kHz to about 1 MHz, from about 100 kHz to about 10 MHz, or from about 10 kHz to about 100 MHz.

[0077] 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 an indication of the waveform from the algorithm and produce an electrical signal representing the electron dose waveform. The signal representing the electron dose waveform may be a lower voltage signal than that provided by the drive electronics to the deflector. The digital pattern generator may receive various parameters related to the shape of the waveform. The parameters may together comprise an indication of the waveform. The various parameters may comprise an indication of any of the properties of the waveform as disclosed herein. The digital pattern generator may receive a synchronization signal from other parts of the microscope as disclosed herein. The pattern generator may be programmable. The pattern generator may be integrated with other sensors and workflows within the microscope, such as those described herein with respect to the sequence generation algorithm. The digital pattern generator may comprise a pulse width modulator. The digital pattern generator may generate DM, PWM, and / or PDM modulation schemes. The digital pattern generator may comprise a digital-to-analog (DAC) converter or an analog-to-digital converter (ADC). In some cases, the digital pattern generator comprises a DAC and / or an ADC to control one or more components of the microscope, for example to synchronize it with the dose waveform.

[0078] In some cases, the electron dose waveform may modulate the average intensity of the electron source directed toward the sample area. In some cases, the average intensity may be modulated without substantially changing other image conditions. For example, the time profile of the waveform may be set, or the alignment of the instrument may be set, but it may be desirable to change the average intensity of the electron dose.

[0079] As shown, a knob 210 may be connected to the digital pattern generator. The knob 210 may be a physical or virtual knob for adjusting the average intensity. In some cases, the average intensity is controllable independently of the drive voltage of the electron source. For example, the average intensity may comprise adjusting the time delay between electron pulses, narrowing the electron pulse duration, or directly adjusting the amplitude of the waveform.

[0080] In some cases, the average intensity is continuously variable across a range of 0-100% dose transmission or 0-100% dose attenuation. Dose attenuation (also referred to as the attenuation 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 attenuation may be expressed as a percentage. Dose transmission may be related to dose attenuation by the relationship: dose transmission=100%-dose attenuation expressed as a percentage.

[0081] In some cases, the average intensity is continuously variable across a range of 0-100% dose transmission or 0-100% dose attenuation in increments of about 30%, about 25%, about 20%, about 15%, about 10%, about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2%, about 1%, about 0.5%, about 0.1%, about 0.05%, about 0.01%, about 0.001%, or less. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, for example, the dose attenuation may be varied in increments within the range of about 30% to about 0.01%, about 10% to about 0.1%, about 30% to about 1%, about 10% to about 0.01%, etc.

[0082] The ratio of pulse width and period (a / b) may be varied over time. For example, it may be varied over the course of 20 seconds. The ratio may be varied over a time period of less than about 100 seconds (s), less than about 50 seconds, less than about 20 seconds, less than about 10 seconds, less than about 5 seconds, less than about 1 second, less than about 500 milliseconds, less than about 250 milliseconds, less than about 100 milliseconds, less than about 50 milliseconds, less than about 20 milliseconds, less than about 10 milliseconds, or less than that. Any of the lower and upper limits described in this paragraph may be combined to form ranges included within the present disclosure, for example, the ratio may be varied over a time period within a range of about 100 seconds to about 1 millisecond, about 100 seconds to about 1 second, or about 50 seconds to about 1 second, etc.

[0083] 3 shows a schematic diagram of a computer or processor-implemented method for modulating dose in a transmission electron microscope image, according to an embodiment. The device may comprise one or more computer processors, such as those described herein with respect to the Processor and Computer section. The one or more computer processors may comprise instructions that, when executed, are configured to implement the methods described herein.

[0084] For example, the processor may receive an indication of an electron dose waveform, e.g., dose waveform 302. The processor may deliver the indication to a pattern generator in the beam deflection system 320a, 320b. The processor may also comprise instructions including method steps for generating a waveform. The processor may also comprise instructions including method steps for adjusting a waveform in response to various parameters. The sequence generation algorithm 140 may comprise one or more of components 304, 306, 308, 310, 312, 314, 316, and 318.

[0085] 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 characteristics of the waveform, such as the time profile of the waveform, according to the image, deflector, driver, detector, or waveform properties to improve measurement quality or respond to external changes to the instrument, or both. Automatic updating of the time profile of the waveform may simplify the user experience by compensating for changes in measurement conditions or by automatically inputting improved measurement settings.

[0086] For example, the one or more parameters may comprise information about one or more of the following: image characteristics from the detector, deflector characteristics, driver electronics characteristics, detector characteristics, and an indication of the electron beam waveform. In some cases, the one or more parameters comprise an indication of a minimum, maximum, or fixed value for the pulse width or pulse repetition rate of the electron beam waveform. For example, the waveform may be adjusted such that the indication of the waveform by the user cannot exceed the functional capabilities of the device. In some cases, the indication of the waveform cannot exceed fixed parameters of the waveform set by the user, such as, for example, that the lamp voltage does not exceed a set level.

[0087] In some cases, the one or more parameters comprise timing constraints of the deflector, driver electronics, or pattern generator. For example, the deflector may be timed so that electrons may pass to the detector during the detector's collection interval. For example, the deflector's pattern generator may be timed so that electrons pass to the detector during the collection interval. For example, the deflection may be synchronized with the readout from the detector over a long period of time. The period of time may be, for example, up to 8 hours or more of data acquisition period. The timing of the deflector and detector may be such that the timing accuracy for the two processes meets a defined performance specification, for example, the synchronization of the two processes is accurate to within 50 milliseconds or better.

[0088] In some cases, one or more parameters comprise a characteristic time scale of the sample or a process within the sample. For example, the electron dose may deform and move the sample, or accumulate heat or net charge on the sample, each of which may lead to a blurred image. In some cases, the structure of the sample may be altered, so that the original structure of interest is no longer visible. Each of these processes may have a characteristic time scale. For example, the effect of the electron dose on the sample may occur at the beginning of the exposure, or may appear for a limited time after the electron beam first touches the sample. These effects may be reduced or disappear at later points in the exposure. Thus, the electron dose waveform may be automatically adjusted, such as by slowly varying the electron dose with time. Varying the dose with time may give the sample an opportunity to adjust as the dose increases or decreases. As another example, the effect of the dose may be mitigated by controlling the duration of short repeated exposures.

[0089] In some cases, the 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 the sample holder, which may change the optimal dose waveform. For example, the electron dose may cause the sample to accumulate heat or a net charge, each of which may lead to a blurred image. For example, the temperature of the sample or the instrument may drift, and the waveform may be adjusted to respond. The waveform may be adapted to increase or decrease the average dose to limit induced voltage or current changes, or to respond to changes in the signal or sample based on heat or charge fluctuations.

[0090] In some cases, the one or more parameters comprise detector dose rate or timing considerations. For example, a deflector may be timed so that electrons may pass to the detector during the detector's collection interval. For example, a waveform may be synchronized with the readout from the detector over a long period of time. The time period may be, for example, a data acquisition period of up to 8 hours or more. The timing of the waveform and detector may be such that the timing accuracy for the two processes meets a defined performance specification, for example, the synchronization of the two processes is accurate to within 50 milliseconds or better.

[0091] In some cases, the one or more parameters comprise an indication of data signal quality from collected or real-time measurements. In some cases, the one or more parameters comprise an indication of the effect of the intensity of the electron dose waveform on the sample from collected or real-time measurements. In some cases, the effect of the dose may reduce the quality of the data. Without being limited by theory, this may be due to, for example, transient charging and / or sample motion. In some cases, it may be advantageous to automatically adjust one or more parameters of the electron dose in response to the real-time image.

[0092] In some cases, a waveform indication from a user may be input to the waveform generator 304. The waveform indication may be input to generate a preliminary waveform 306.

[0093] In some cases, the preliminary waveform 304 may be adjusted according to one or more constraints 308. The constraints may comprise an indication of a minimum, maximum, or fixed value for the pulse width or pulse repetition rate of the electron beam waveform. In this way, the user's indication of the waveform may not exceed the functional capabilities of the device. In some cases, the indication of the waveform may not exceed fixed parameters of the waveform set by the user, such as, for example, that the lamp voltage does not exceed a set level. In some cases, the constraints may comprise timing constraints of the deflector, driver electronics, or pattern generator. In this way, the user's indication of the waveform may not exceed the functional capabilities of the device. In some cases, the constraints may comprise characteristic time scales of the sample or processes within the sample. For example, the user may know the bleaching time or sample destruction time based on an understanding of the sample or processes within the sample. The waveform may be automatically adapted to limit the average exposure to limit such processes. The constraints may comprise the collection time of the detector, the location of one or more sub-portions of the detector, the arrival time of the stimulus to the sample area, or the timing of the electron dose waveform relative to changes in the electron optical conditions of the device.

[0094] One or more constraints 308 may be used to generate an updated waveform 312 using a waveform generator 310. In some cases, the updated waveform may be delivered to a pattern generator in the beam deflection system 320a. The updated waveform may comprise an indication of the waveform to be delivered to the pattern generator. Although FIG. 3 shows the use of constraints 308, in some cases, constraints may not be used. For example, a preliminary waveform 306 may be fed directly to the waveform generator 316, with or without the use of real-time sensor information.

[0095] In some cases, the electron dose waveform may be adjusted according to one or more parameters in response to real-time sensor information 314. The real-time sensor information may comprise a time-dependent voltage bias or temperature. For example, the temperature of the sample or the instrument may drift and the waveform may be adjusted to respond. For example, the waveform may be adjusted for drift in the electron acceleration voltage, or the charge of the sample, or stray magnetic fields. The real-time sensor information may comprise a detector dose rate or timing considerations. For example, the waveform may be modified if the detector dose rate begins to exceed a detector threshold. For example, the waveform may be modified if this exceeds the detector's temporal response time. The real-time sensor information may comprise an indication of data signal quality from collected or real-time measurements. The real-time sensor information may comprise an indication of the effect of the intensity of the electron dose waveform on the sample from collected or real-time measurements. For example, if the sample begins to lose signal, the waveform may be modified to increase the intensity and raise the signal. Real-time sensor information may comprise detector collection time, location of one or more sub-portions of the detector, arrival time of the stimulus to the sample area, or timing of the electron dose waveform relative to changes in the electronic optical conditions of the device.

[0096] The real-time sensor information 314 may be used to generate a second updated waveform 318 using a waveform generator 316. In some cases, the second updated waveform may be delivered to a pattern generator in the beam deflection system 320b. The updated waveform may comprise an indication of the waveform to be delivered to the pattern generator.

[0097] In some cases, the real-time sensor information may be used to generate a third updated waveform, a fourth updated waveform, or more. The real-time sensor information may be repeatedly fed back to the waveform generator 316. For example, the real-time sensor information may be used to update the waveform every 10 seconds, every 1 second, every 100 milliseconds, every 10 milliseconds, every 1 millisecond, every 100 nanoseconds, every 10 nanoseconds, every 1 nanosecond, or less. The waveform generator may be updated substantially in real time. In some cases, the real-time sensor information may be directed to the beam deflection system 320b.

[0098] 4 shows a schematic diagram of a method for modulating dose in an electron microscope image, according to an embodiment. In operation 410, the method 400 may include providing an electron source directed toward a sample area. The electron source may comprise source 102 of FIG. 1. The sample area may comprise sample area 110 of FIG. 1.

[0099] In operation 420, the method 400 may include receiving an electron beam waveform at a deflector disposed between the electron source and the sample area. The deflector may comprise deflector 106 of FIG. 1. The electron beam waveform may modulate an intensity of the electron source directed at the sample area. The electron beam waveform may comprise any of the waveforms including any or all variable parameters as disclosed herein. The electron beam waveform may have any of the characteristics disclosed herein with respect to FIG. 1. The electron beam waveform may be generated by any method herein, such as that described with respect to FIG. 3.

[0100] For example, modulation of the electron source by a deflector can be associated with an electron dose waveform. The waveform provided may modulate the amount of electrons (e.g., dose) arriving at the sample area. In some cases, the waveform may determine a time profile of the average dose at the sample area. In some examples, a waveform that determines a time profile of the average dose may be provided.

[0101] In some cases, the method 400 further includes receiving an indication of a time profile of the average dose from a user. The indicated time profile may be converted to a waveform. The conversion to a waveform may be performed or assisted by a processor with instructions as disclosed herein. The waveform may be an on-off waveform that varies the average dose with time. The waveform may be amplified to an operating voltage and applied to a high-speed electrostatic deflector.

[0102] The electron dose waveform may have an arbitrarily defined time profile. The arbitrarily defined electron dose profile may be a profile that is not dictated by a regular periodic function. The regular periodic function may include a pulse pattern or a regular pulse pattern, such as a square wave, a sinusoid, 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 forearm function. The arbitrarily defined electron dose waveform may be an electron dose waveform that does not have a regular pulse width or that does not have a regular repetition rate, or that does not have both. The arbitrarily defined electron dose waveform may be an electron dose waveform that has a selectable irregular pulse width or that has a selectable irregular repetition rate, or that has both. The arbitrarily defined time profile may be a time profile that is determined by an arbitrarily defined waveform. The arbitrary waveform may be generated or input by a user. In some cases, the method 400 includes receiving an indication of an irregular pulse width or a series of irregular pulse widths from a user.

[0103] In some cases, the arbitrarily defined electron dose profile may comprise a dose profile with a series of points (e.g., waypoints). The waveform may be interpolated from the series of points. The series of waypoints can be individually or collectively selected to construct the arbitrarily defined time profile. In some cases, the method 400 further includes receiving an indication of the arbitrarily defined time profile from a user. In some cases, the method 400 further includes receiving a user provided function and / or generating a series of waypoints. In some cases, the method 400 further includes receiving an indication from a user of an individual waypoint or set of waypoints to be moved and / or varying the waveform in response. In some cases, the electron dose waveform is non-periodic.

[0104] In some cases, the method 400 further includes generating a waveform. For example, generating the waveform may include adjusting the waveform in response to various parameters, such as one or more parameters described herein with respect to FIG. 3. In some cases, the method 400 further includes implementing a sequence generation algorithm 140. Implementing may further include implementing one or more of components 304, 306, 308, 310, 312, 314, 316, and 318 as described with respect to FIG.

[0105] In some cases, the method 400 further includes one or more of the following: receiving an indication of an electron dose waveform in a waveform generator 304; generating an initial or preliminary waveform 306; adjusting the preliminary waveform 304 according to one or more constraints 308; iteratively updating the indication of the waveform to match or substantially match the constraints 310; generating an updated waveform 312; adjusting the waveform according to one or more parameters in response to real-time sensor information 314; iteratively updating the indication of the waveform to match or substantially match the real-time sensor information 316; and outputting the corrected waveform to a deflector.

[0106] At operation 420, the method 400 may include outputting an electronic or electron-induced signal associated with at least a portion of the modulated intensity. In some cases, the electronic signal comprises a signal that has propagated through the sample area. The electronic signal may be collected from the detector 104 of FIG. 1. The electronic signal may comprise all or a portion of the image and / or associated image data for any of the electron microscopy images as disclosed herein.

[0107] Processors and Computers: In some cases, the disclosed systems may comprise one or more processors, computers, or computer systems configured to modulate the electron dose, including, for example, control, configuration, and synchronization of the electron dose modulation, and storage, processing, analysis, and display of acquired sensor data or applied modulation patterns. In some cases, the one or more processors, computers, and computer systems may be configured for control of other system functions and / or other data acquisition, storage, processing, analysis, or display functions as well.

[0108] Disclosed herein is a computer-implemented method for modulating an electron dose on an electron microscope, such as a transmission electron microscope or any other electron microscope disclosed herein. The method may include receiving, in a processor, an indication of an electron dose waveform comprising a representation of a time profile of an intensity of an electron dose directed to a sample area in the electron microscope. The method may include transmitting the indication to the electron microscope. For example, an electrical signal representing the indication may drive a deflector in the electron microscope to modulate the time profile of the electron dose. The method may include receiving one or more adjustable parameters, such as those disclosed herein with respect to FIG. 3. For example, the one or more adjustable parameters may comprise information about one or more of a property of an image, a property of a deflector, a property of driver electronics in the microscope, a property of a detector in the microscope, and an indication of an electron dose waveform. The method may include updating the indication of the electron dose waveform based on the one or more parameters.

[0109] In some cases, the method includes continuously updating an indication of the electron dose waveform. The method may include the use of a processor to perform one or more of the operations of the methods described herein. For example, the processor may receive an indication of an electron dose waveform, e.g., dose waveform 302. The processor may deliver the indication to a pattern generator in the beam deflection system 320a, 320b. The processor may also include instructions including method steps for generating a waveform. The processor may also include instructions including method steps for adjusting a waveform in response to various parameters. The sequence generation algorithm 140 may include one or more of components 304, 306, 308, 310, 312, 314, 316, and 318.

[0110] 7 provides a schematic illustration of a computer system 701 programmed or otherwise configured to implement methods described elsewhere herein (e.g., electron dose waveform methods, methods described herein, etc.). The computer system 701 can coordinate various aspects of the disclosed methods and systems, such as, for example, obtaining and processing diffraction pattern data, image data, STEM data, spectroscopic data, or any combination thereof. The computer system 701 may comprise a local computer system, a user's electronic device (e.g., a smartphone, laptop, or desktop computer), or a user's electronic device in communication with a computer system located remotely relative to the electronic device. The computer system 701 may be a post-classical computer system (e.g., a quantum computing system).

[0111] The computer system 701 includes a central processing unit (CPU, also referred to herein as a "processor" or "computer processor") 705, which may be a single-core or multi-core processor, or multiple processors for parallel processing. The computer system 701 also includes a memory or memory location 710 (e.g., random access memory, read-only memory, flash memory), an electronic storage unit 715 (e.g., a hard disk), a communication interface 720 (e.g., a network adapter) for communicating with one or more other systems, and peripheral devices 725, such as cache, other memory, data storage devices, and / or electronic display adapters. The memory 710, the storage unit 715, the interface 720, and the peripheral devices 725 communicate with the CPU 705 through a communication bus (solid lines) such as a motherboard. The storage unit 715 may be a data storage unit (or data repository) for storing data. The computer system 701 may be operatively coupled to a computer network ("network") 730 using the communication interface 720. Network 730 may be the Internet, an intranet and / or an extranet, or an intranet and / or an extranet in communication with the Internet. Network 730 is, in some cases, a telecommunications and / or data network. Network 730 may include one or more computer servers, which may enable distributed computing, such as cloud computing. Network 730 may, in some cases, implement a peer-to-peer network with computer system 701, which may enable devices coupled to computer system 701 to behave as clients or servers.

[0112] CPU 705 is configured to execute sequences of machine-readable instructions, which may be embodied in a program or software. The instructions may be stored in a memory location, such as memory 710. The instructions may be directed to CPU 705, which may subsequently program or otherwise configure CPU 705 to implement the methods of the present disclosure. Examples of operations performed by CPU 705 may include fetch, decode, execute, and writeback.

[0113] The CPU 705 may be part of a circuit, such as an integrated circuit. One or more other components of the system 701 may be included in the circuit. In some cases, the circuit is an application specific integrated circuit (ASIC).

[0114] The storage unit 715 is configured to store files such as drivers, libraries, and saved programs. The storage unit 715 may also store user data, such as user preferences and user programs. The computer system 701 may in some cases include one or more additional data storage units external to the computer system 701, such as a data storage unit located on a remote server that communicates with the computer system 701 through an intranet or the Internet.

[0115] Computer system 701 may communicate with one or more remote computer systems through network 730. For example, computer system 701 may communicate with a user's remote computer system (e.g., a cloud server). Examples of remote computer systems include a personal computer (e.g., a desktop PC), a portable personal computer (e.g., a laptop or tablet PC), a smartphone (e.g., an Apple iPhone®, an Android®-enabled device, etc.), or a personal digital assistant. A user may access computer system 701 via network 730.

[0116] Software and Algorithms: As discussed above, in some cases, the disclosed system may further comprise software for (i) providing an electron source directed toward the sample area, (ii) receiving an electron dose waveform at a deflector disposed between the electron source and the sample area, the electron dose waveform modulating an intensity of the electron source directed toward the sample area according to the electron dose waveform, and (iii) outputting an electronic or electron-induced signal related to at least a portion of the modulated intensity. In some cases, the electronic signal comprises a signal propagated through the sample area. In some cases, the processor may comprise software for implementing one or more steps of the sequence generation algorithm 140, such as one or more of components 304, 306, 308, 310, 312, 314, 316, and 318. In some cases, the processor may comprise software for control of other system functions and / or other data acquisition, storage, processing, analysis, or display functions as well.

[0117] In some cases, the methods described herein may be implemented using machine (e.g., computer processor) executable code stored on an electronic storage location of a computer system such as that illustrated in FIG. 7 (e.g., in memory 710 or electronic storage unit 715 of computer system 701, etc.). The machine executable or machine readable code may be provided in the form of software. During use, the code may be executed by the processor 705. In some cases, the code may be read from the storage unit 715 and stored on the memory 710 for rapid access by the processor 705. In some situations, the electronic storage unit 715 may be omitted and the machine executable instructions are stored on the memory 710.

[0118] In some cases, the code can be pre-compiled and configured for use with a machine having a processor adapted to execute the code. In some cases, the code may be compiled during run-time. The code can be provided in a programming language that can be selected to allow the code to be executed in a pre-compiled or as-compiled manner.

[0119] Aspects of the methods and systems provided herein, such as computer system 701, can be embodied in programming. Various aspects of the technology can be considered as a "product" or "article of manufacture" typically in the form of machine (or processor) executable code and / or associated data carried on or embodied in some type of machine-readable medium. The machine executable code can be stored on an electronic storage unit, such as in memory (e.g., read-only memory, random access memory, flash memory) or on a hard disk. A "storage" type medium can include any or all of the tangible memory of a computer system, computer processor, or equivalent, or its associated modules, such as various semiconductor memory devices, tape drives, disk drives, optical drives, and the like, that can provide non-transitory storage at any time for software programming. All or a portion of the software may be communicated from time to time over the Internet or various other telecommunications networks. Such communication may, for example, enable loading of the software from one computer or processor to another, for example, from a management server or host computer to a computer platform of an application server. Thus, 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 the like, may also be considered software-bearing media. As used herein, unless limited to non-transitory tangible "storage" media, terms such as computer or machine "readable medium" refer to any medium that participates in providing instructions to a processor for execution.

[0120] Thus, a readable medium such as a computer executable code may take many forms, including, but not limited to, a tangible storage medium, a carrier wave medium, or a physical transmission medium. Non-volatile storage media include, for example, optical or magnetic disks, such as any of the storage devices in any computer or equivalent that may be used to implement a database. Volatile storage media include dynamic memory, such as the main memory of such a computer platform. Tangible transmission media include copper wire and optical fibers, including coaxial cables, i.e., the wires that comprise a bus in a computer system. Carrier wave transmission media may take the form of electric or electromagnetic signals, or acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer readable media thus include, for example, floppy disks, flexible disks, hard disks, magnetic tape, any other magnetic media, CD-ROMs, DVDs or DVD-ROMs, any other optical media, punch cards paper tape, any other physical storage media with patterns of holes, RAM, ROM, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cartridges, carrier waves that transport data or instructions, cables or links that transport such carrier waves, or any other medium from which a computer may read programming code and / or data. Many of these forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.

[0121] The computer system 701 may include or be in communication with an electronic display 735 that includes a user interface (UI) 740 to provide an interface for a user to, for example, enter instructions, upload data to a computer database, download data from a computer database, etc. Examples of a UI include, but are not limited to, a graphical user interface (GUI) and a web-based user interface.

[0122] In some cases, the methods and systems of the present disclosure may be implemented through the use of one or more algorithms, e.g., algorithms comprising instructions for obtaining and / or processing diffraction pattern data, image data, and the like. The algorithms may comprise sequence generation algorithm 140, e.g., algorithms including one or more of components 304, 306, 308, 310, 312, 314, 316, and 318. The algorithms may be implemented using software, responsive to execution by central processing unit 705.

[0123] Working Example The following examples are given for the purpose of illustrating various embodiments of the present invention, and are not meant to limit the present invention in any manner. The examples, together with the methods described herein, represent currently preferred embodiments, are exemplary, and are not intended as limitations on the scope of the present invention. Modifications therein and other uses encompassed within the spirit of the present invention as defined by the scope of the claims will occur to those skilled in the art.

[0124] FIG. 5 shows examples of high-resolution TEM images taken with various dose decays using electron dose waveforms modulated by a deflector. The first dose waveform (500) has a pulse width of 5 microseconds and a period (defined as the time between the rising edges of adjacent pulses) of 10 microseconds. The average illumination rate (510) is 50%. The second dose waveform (520) is always on and has an average illumination rate of 100%. The TEM image taken at a dose rate of 50% (530) does not show any significant distortion or blurring compared to the image at a dose rate of 100% (540). However, the average number of detected electrons per pixel in image 530 is half as large as in image 520. The images were taken at an accelerating voltage of 200 kV using a sample of gold nanoparticles on a carbon grid. The dose decays described elsewhere herein comprise dose rate values ​​expressed as 100%-percentages.

[0125] FIG. 6 shows a schematic diagram of an electron microscopy experiment using an electron dose waveform modulated by a deflector. The schematic shows pulsed illumination that varies over time as the experiment progresses to accommodate a detector that can handle low electron dose rates. During phase A, the dose waveform (600) is at 100% intensity and the detector (620) is disabled. A high electron dose initiates the focus process on the sample. During phase B, the dose waveform (600) transitions to a pulsed mode with an average intensity (610) of 25%. The reduced intensity during phase B is consistent with the optimal operating range of the detector. The detector is enabled during phase B, and the detector records the response of the sample to the high electron dose applied during phase A. The dose decay can be continuously varied over time, allowing for continuously variable or intermittent pulse modulation.

[0126] Tables 1 and 2 show exemplary use modes for a deflector configured to modulate an electron dose waveform as described herein. For example, the deflector may be used as a high-speed electron beam blanker for various imaging modalities. For example, the deflector may be used to attenuate the electron beam and / or to perform experiments with some control over the shape of the electron beam. These potential uses should not be considered limiting. In some cases, various products may be shipped with capabilities for one or both of the exemplary modes shown in Tables 1 and 2.

[0127] Table 1 below shows exemplary values ​​for maximum pulse duration, transition time, minimum pulse width, and number of blanking signal inputs at various accelerating voltages. One exemplary implementation of the electron dose waveform modulation described herein is a high-speed beam blanking system for providing accurate electron microscopy images, for example, in transmission or reflection modalities. [Table 1]

[0128] Table 2 below shows exemplary maximum pulse repetition frequency, minimum repetition frequency, and duration for various electron dose modulation types. An exemplary implementation of the electron dose waveform modulation described herein is a fast attenuation and / or beam shaping application for electron microscopy imaging, for example, in transmission or reflection modalities. The table also shows potential applications for each dose modulation type. For example, Type A may be more useful for TEM imaging, and Type B may be more useful for TEM and / or STEM and / or pump probe imaging. These potential applications should not be considered limiting. For example, Type B may be more useful for TEM imaging, and Type A may be more useful for TEM and / or STEM and / or pump probe imaging. In some cases, various products may be shipped with capabilities for one or both of Type A and Type B. [Table 2]

[0129] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the present invention. It is understood that the various alternatives to the embodiments of the present invention described herein may be employed in any combination in practicing the present invention. It is intended that the following claims define the scope of the present invention, and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. It is a device, An electron source directed toward the sample area, A detector configured to receive an electronic signal or an electronically induced signal, A deflector positioned between the electron source and the sample area, wherein the deflector is configured to modulate the intensity of the electron beam from the electron source directed toward the sample area according to an electron dose waveform having a continuously variable time profile. A device equipped with the following features.

2. The device according to claim 1, wherein the continuous variable time profile comprises a selectable irregular pulse width, a selectable irregular repetition rate, or both.

3. The device according to claim 1, wherein the electron dose waveform is an arbitrary waveform.

4. The device according to claim 1, wherein the electron dose waveform comprises a series of intermediate points, and the electron dose waveform is interpolated from the series of intermediate points.

5. The device according to claim 3, wherein the electron dose waveform comprises a series of intermediate points, and the series of intermediate points can be selected one by one to construct the arbitrary waveform, or the series of intermediate points can be selected as a set.

6. The device according to claim 3, wherein the arbitrary waveform has a time resolution of less than 10 nanoseconds.

7. The device according to claim 3, wherein the arbitrary waveform is indicated by the user.

8. The device according to claim 1, wherein the electron dose waveform modulates the average intensity of the electron source directed toward the sample area.

9. The device according to claim 8, wherein the average intensity is substantially modulated without altering other image conditions.

10. The device according to claim 8, further comprising a physical or virtual knob for adjusting the average intensity.

11. The device according to claim 8, wherein the average intensity is controllable independently of the drive voltage of the electron source.

12. The device according to claim 1, wherein the electron dose waveform comprises a periodic waveform, a pump pulse and a probe pulse, or a square wave.

13. The device according to claim 1, wherein the electron dose waveform is aperiodic.

14. The device according to claim 1, wherein the transition time between high voltage and low voltage is less than approximately 50 nanoseconds, defined as the sum of ringing time and slope time.

15. The device according to claim 1, wherein the transition time between high voltage and low voltage is less than about 10 nanoseconds, defined as the slope time of the transition voltage from about 10% to about 90%.

16. The device is A pattern generator configured to generate an electrical signal representing the electron 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 to the deflector, The device according to claim 1, further comprising:

17. The device further comprises one or more computer processors, The one or more computer processors mentioned above are Receiving the indication of the electron dose waveform, To deliver the indication to the pattern generator The device according to claim 16, which is programmed to perform the following actions individually or as a set.

18. The device according to claim 17, wherein the one or more computer processors are programmed individually or collectively to adjust the shape of the electron dose waveform according to one or more parameters.

19. The one or more of the above parameters are, Information regarding one or more of the following: the properties of the image from the detector, the properties of the deflector, the properties of the driver electronic equipment, the properties of the detector, and the indication of the electron dose waveform, Indication of a minimum, maximum, or fixed value relating to the pulse width or pulse repetition rate of the electron dose waveform, Timing constraints of the deflector, the driver electronic device, or the pattern generator, A timescale of a sample or a timescale of a process within the sample, wherein the timescale is the duration associated with deformation, movement, heat accumulation, net charge change, or structural change of the sample, Time-dependent voltage bias or temperature, The dose rate of the aforementioned detector and Indication of data signal quality from collected measurements or real-time measurements and Indication of the effect of the intensity of the electron dose waveform on a sample from collected measurements or real-time measurements and The device according to claim 18, comprising one or more elements selected from the group consisting of the following.

20. The device according to claim 18, wherein the one or more computer processors are programmed individually or collectively to adjust the acquisition time of the detector, the location of one or more subparts of the detector, the arrival time of a stimulus to the sample area, or the timing of the electron dose waveform in response to a change in the electro-optical conditions of the device.

Images