Method of operating a charged particle microscope system including a beam deflector and related system

Abstract

To provide a method for operating a charged particle microscope (CPM).SOLUTION: In one example, the method includes adjusting one or more optical elements such that a deflector plane of the beam deflector is conjugate to the diffraction plane, and recording the diffracted beam pattern at the diffraction plane. The method includes directing a charged particle beam to a sample, transitioning a beam blanker between a blanked state and an unblanked state, and recording a beam pattern with a detector. The beam pattern includes one or more beam pattern features that are substantially stationary in the detector plane when the beam blanker transitions between the unblanked state and the blanked state. The CPM system includes a charged particle source, a beam deflector at a deflector plane, and a detector, configured such that the charged particle beam exhibits a beam crossover at the deflector plane and the deflector plane is imaged onto the detector.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates generally to methods of operating a charged particle microscope including a beam deflector, and more particularly to methods of configuring a transmission electron microscope for use with a beam deflector in electron diffraction experiments. [Background technology]

[0002] Charged particle microscopy, specifically in the form of electron microscopy, is a well-known and increasingly important technique for imaging microscopic objects. The basic type of electron microscope is implemented in various instrumental types, such as transmission electron microscopes (TEM), scanning electron microscopes (SEM), and scanning transmission electron microscopes (STEM), as well as various subtypes.

[0003] In an SEM, irradiation of a sample by a scanning electron beam causes the sample to emit "auxiliary" radiation in the form of, for example, secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible, and / or ultraviolet photons). One or more components of this emitted radiation are then detected and used to build up an image.

[0004] As an alternative to using electrons as the illuminating beam, charged particle microscopy can also be performed using other species of charged particles. In this regard, the phrase "charged particles" can be understood to encompass, for example, electrons, positive ions (e.g., gallium (Ga) ions or helium (He) ions), negative ions, protons, and positrons. In addition to imaging and performing (local) surface modifications (e.g., milling, etching, deposition, etc.), charged particle microscopes can also have other functionalities, such as performing spectroscopy, examining diffractograms, etc.

[0005] In all cases, a charged particle microscope (CPM) will generally comprise at least a radiation source (eg, an electron source or ion gun), a beam guidance system, a sample holder, and a detector.

[0006] Detectors can take many different forms depending on the radiation being detected. Examples include photodiodes, CMOS detectors, CCD detectors, photovoltaic cells, X-ray detectors (such as silicon drift detectors and silicon lithium (Si(Li)) detectors), etc. In general, a CPM may include several different types of detectors, and the choice of detector may be guided by different circumstances. In general, it is desirable for the detector to exhibit a dynamic range wide enough to represent a wide range of incident charged particle signal magnitudes.

[0007] Although the present disclosure relates generally to the specific context of charged particle microscopy, and more particularly to transmission electron microscopy, such description is not intended to be limiting, and it is within the scope of the present disclosure that the apparatus and methods disclosed herein may be applied in any suitable context. Summary of the Invention

[0008] Disclosed herein is a method for operating a charged particle microscope (CPM) system that includes a beam deflector and associated systems.

[0009] In a representative example, a method of operating a CPM system includes adjusting one or more optical elements of the CPM system so that a deflector plane in which a beam deflector is positioned is conjugate with a diffraction plane in which a charged particle beam directed at a sample produces a diffraction beam pattern, and the method additionally includes recording the diffraction beam pattern with a detector positioned at the diffraction plane.

[0010] In another exemplary embodiment, a method of operating a CPM system includes directing a charged particle beam toward a sample, the sample adjusting the charged particle beam to create a beam pattern downstream of the sample. The method additionally includes transitioning a beam blanker of the CPM system between an unblanked state and a blanked state. The beam blanker is positioned at a deflector plane. When the beam blanker is in the unblanked state, the charged particle beam reaches the sample. When the beam blanker is in the blanked state, the charged particle beam is directed away from the sample. The method additionally includes recording the beam pattern using a detector positioned at a detector plane conjugate to the deflector plane. The beam pattern includes one or more beam pattern features focused in the detector plane. The one or more beam pattern features are substantially stationary in the detector plane when the beam blanker transitions between the unblanked state and the blanked state.

[0011] In another representative example, a CPM system includes a charged particle source, a first optical assembly positioned downstream from the charged particle source, and a beam deflector positioned at a deflector plane downstream from the first optical assembly. The charged particle source is configured to emit a charged particle beam along an optical axis toward a sample. The beam deflector is configured to selectively redirect the charged particle beam away from the sample. The CPM system additionally includes a second optical assembly positioned downstream from the deflector plane and a detector positioned at a detector plane downstream from the second optical assembly. The CPM system is configured such that the charged particle beam exhibits a beam crossover at the deflector plane and such that the deflector plane is imaged onto the detector.

[0012] The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic, illustrative diagram of a charged particle microscope (CPM) system in accordance with an example. [Figure 2] 1 is a schematic diagram of a charged particle beam path through a CPM system according to an example. [Figure 3A] 1 is a schematic diagram of the paths of a charged particle beam and a partially deflected beam through a CPM system in an initial configuration, according to an example. [Figure 3B] 1 is a schematic diagram of a path of a charged particle beam and a partially deflected beam through a CPM system in an intermediate configuration, according to an example. [Figure 3C] 1 is a schematic diagram of a path of a charged particle beam and a partially deflected beam through a CPM system in a conjugate blanking configuration, according to an example. [Figure 4] 1 is an illustrative diagram of streaks formed by an electron beam traversing a detector, according to an example. [Figure 5A] FIG. 1 is an illustrative diagram of a diffraction pattern recorded with a CPM system in an initial configuration, according to an example. [Figure 5B] FIG. 5B is an illustration of the diffraction pattern of FIG. 5A recorded after bringing the CPM system into a conjugate blanking configuration. [Figure 6A] FIG. 10 is an illustrative diagram of a diffraction pattern recorded with a CPM system in an initial configuration, according to another example. [Figure 6B] FIG. 6B is an illustration of the diffraction pattern of FIG. 6A recorded after bringing the CPM system into a conjugate blanking configuration. [Figure 7] 1 is a flowchart illustrating a method of operating a CPM system, according to an example. [Figure 8] 10 is a flowchart illustrating a method of operating a CPM system, according to another example. [Figure 9] 1 is a schematic diagram of a computing system that may be used to implement one or more methods of the present disclosure, according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present disclosure is generally directed to methods of configuring and / or operating a CPM system, such as a TEM, in a manner that reduces and / or eliminates undesired changes in diffraction patterns when beam deflectors are operated to blank or unblanket a charged particle beam. As described in more detail below, such beam deflectors may operate by selectively directing the charged particle beam to block blanking structures, such as apertures, before reaching a sample.

[0015] CPM systems may employ beam deflectors for any of a variety of purposes. As one example, a beam deflector can selectively redirect a charged particle beam away from a sample to shield a sensitive sample from the charged particle beam when the CPM system is not actively imaging the sample. As another example, switching such a beam deflector between blanked and unblanked states can enable the charged particle beam to be delivered to the sample in pulses of controlled duration. For example, when using a sufficiently fast beam deflector, it is possible to generate charged particle beam pulses on microsecond, nanosecond, or even sub-nanosecond time scales. Recording signals (e.g., in the form of diffraction patterns) created by charged particle pulses traversing a sample can be used in damage mitigation studies and / or time-resolved studies of sample behavior in a pump-probe setup.

[0016] Beam deflectors can generally be characterized by the transition time for transitioning between a fully blanked state and a fully unblanked state. In many instances, blanking or unblanking of a charged particle beam can cause the diffracted charged particle beam to move within the diffraction plane where the diffraction pattern is recorded, thus causing visible streaking of the diffraction pattern during such periods. In applications where the pulse length of the charged particle beam is short relative to the characteristic transition time of the beam deflector, such streaking can become increasingly noticeable in the exposure that captures the recorded diffraction pattern, thus limiting the precision with which the intended diffraction pattern can be recorded.

[0017] Accordingly, the present disclosure is directed to methods for configuring a CPM system so that the features of the diffraction pattern are at least substantially stationary in the diffraction plane in which the diffraction pattern is recorded. As described in more detail below, this can be achieved by positioning a beam deflector in a plane that is conjugate to the diffraction plane. Examples of how such a configuration can be achieved are provided below.

[0018] Exemplary System Figure 1 shows an example of a CPM system 100 that can be used in practicing embodiments of the methods disclosed herein. In particular, Figure 1 illustrates a CPM system in the form of a transmission electron microscope (TEM).

[0019] 1, the CPM system 100 includes a vacuum enclosure 102 and an electron source 104 (e.g., a Schottky emitter) positioned within the vacuum enclosure 102. The electron source 104 generates an electron beam 106 that traverses an illuminator 110, which directs and / or focuses the electron beam 106 onto a portion of a sample 140. The illuminator 110 has an optical axis 108 and may include any of a variety of electrostatic / magnetic lenses, a deflector 112, a corrector (e.g., an astigmatism corrector), etc. The illuminator 110 may also include and / or be a condenser system.

[0020] In the example of FIG. 1 , the sample 140 is held on a sample holder 114. As illustrated herein, a portion of the sample holder 114 extends into the housing 102 and is attached to a cradle 116 that can be positioned / moved with multiple degrees of freedom by a positioning device (stage) A. For example, the cradle 116 may be displaceable in the X, Y, and Z directions shown in FIG. 1 and / or rotated about a longitudinal axis parallel to the X direction. Such movement may allow different portions of the sample 140 to be illuminated / imaged / inspected by the electron beam 106 moving along the optical axis 108. Such movement may additionally or alternatively allow selected portions of the sample 140 to be machined, for example, by a focused ion beam (not shown). Additionally or alternatively, in some examples, the electron beam 106 may be scanned relative to the sample 140 using one or more deflectors 112.

[0021] The (focused) electron beam 106 traveling along the optical axis 108 may interact with the sample 140 in such a way as to cause various types of "stimulating" radiation to be emitted from the sample 140, including (for example) secondary electrons, backscattered electrons, X-rays, and optical radiation (cathodoluminescence). One or more of these radiation types may be detected using a sensor 122, which may be, for example, a combined scintillator / photomultiplier tube or an EDX (Energy-Dispersive X-Ray Spectroscopy) module. In one such example, an image may be constructed using essentially the same principles as in an SEM. Additionally or alternatively, electrons that traverse (pass through) the sample 140, emerge (emit) from the sample 140, and continue propagating along the optical axis 108 (substantially, but generally with some deflection / scattering) may be studied. This transmitted electron flux enters an imaging system (eg, a compound objective / projection lens) 124, which may include a variety of electrostatic / magnetic lenses, deflectors, correctors (such as astigmatism correctors), and the like.

[0022] In normal (non-scanning) TEM mode, this imaging system 124 may focus the transmitted electron beam onto a phosphor screen 126, which may be retracted / extended (schematically indicated by arrow 126') relative to the optical axis 108 if desired. An image (e.g., a diffractogram) of at least a portion of the sample 140 is formed on the screen 126 by the imaging system 124, and this image may be viewed through a viewing port 128 located in a suitable portion of a wall of the housing 102. The retraction mechanism for the screen 126 may, for example, be mechanical and / or electrical in nature.

[0023] 1, CPM system 100 may include a TEM camera 130. At the location of TEM camera 130, the electron beam may form a still image (or diffractogram), which may be processed by controller 150 and displayed on a display device, such as a flat panel display. When not needed, TEM camera 130 may be retracted / extended relative to optical axis 108 (as indicated generally by arrow 130').

[0024] Additionally or alternatively, as shown in FIG. 1 , the CPM system 100 may include a STEM detector 132. The output from the STEM detector 132 may be recorded as a function of the scanning position (X, Y) of the electron beam 106 on the sample 140, constructing an image that is a “map” of the output from the STEM detector 132 as a function of (X, Y). In existing tools, the STEM detector 132 may include a single pixel having, for example, a 20 mm diameter, as opposed to the matrix of pixels typically present in the TEM camera 130. Again, when not needed, the STEM detector 132 may be retracted / extended relative to the optical axis 108 (as shown schematically by arrow 232′).

[0025] Additionally or alternatively, as shown in FIG. 1, CPM system 100 may include spectroscopic device 134, which may include and / or be an EELS module, for example.

[0026] It should be noted that the order / location of items 130, 132, and 134 is not strict and many possible variations are possible. For example, spectroscopic device 134 could also be integrated with imaging system 124.

[0027] A controller / computer processor 150 is connected to the various components illustrated via control lines (bus) 152. This controller 150 may provide various functions, such as synchronizing operations, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not shown in FIG. 1 ). The controller 150 may be located at least partially inside or outside the enclosure 102, as desired, and may be of unitary or composite construction. Those skilled in the art will appreciate that the interior of the enclosure 102 need not be maintained at a strict vacuum. For example, in so-called "environmental (S)TEMs," a background atmosphere of a given gas is intentionally introduced / maintained within the enclosure 102. Those skilled in the art will also appreciate that in practice it may be advantageous to confine the volume of the housing 102 so that, if possible, the housing extends essentially minimally away from the axis 108, and the employed electron beam passes through the small diameter tube, but expands to accommodate structures such as the source 104, sample holder 114, screen 126, camera 130, detector 132, spectrometer 134, etc.

[0028] In some examples, the illuminator 110 may include beam-shaping elements, such as lenses and / or aperture plates / diaphragms, to appropriately shape (focus) the beam 106 into a relatively narrow "pencil" of charged particles so that only a relatively small area (footprint) of the sample 140 is irradiated at any given time. Relative motion between the sample 140 and the footprint of the beam 106 to move the footprint onto a different area of ​​the sample can be generated in any of a variety of ways, such as by moving the sample 140 relative to the beam 106 using the positioning device 118 and / or by deflecting the beam 106 relative to the sample 140 using the deflector 112, by moving the source 104 and / or the beam-shaping elements described above to displace the beam 106 relative to the sample 140.

[0029] In some examples, the TEM camera 130 may be used to capture a diffractogram (diffraction pattern) at each such selected position of the electron beam 106 relative to the sample 140. Specifically, the controller 150 (or another processor device) may be programmed and / or configured to obtain a set of ptychographic measurements by recording the output of (for example) the TEM camera 130 for each of a series of different positions of the beam 106 on the sample 140 (achieved, for example, by sending an appropriate series of set points to the positioning device 118, the deflector 112, etc.). Additionally or alternatively, the controller 150 may be programmed and / or configured to process the recorded outputs of the camera 130 and use them as input for implementing a mathematical reconstruction algorithm. Additionally or alternatively, the controller 150 may be programmed and / or configured to display the results of the reconstruction algorithm, for example, in the form of an image on a display device (not shown).

[0030] Conjugate Blanking Configuration 2 illustrates an embodiment of an electron beam 202 traversing elements of a TEM 200 configured in accordance with the present disclosure. The TEM 200 may be described as representing an example of the CPM system 100 of FIG. 1 and may share any components, attributes, etc. with the CPM system 100 of FIG.

[0031] While this disclosure generally relates to examples in which the CPM system under consideration is a TEM (e.g., TEM 200) and the charged particle beam is an electron beam (e.g., electron beam 202), this is not required in all examples. For example, it is within the scope of this disclosure that the methods and concepts disclosed herein may be applicable to any suitable CPM system and / or other optical systems, such as STEM, SEM, and / or optical microscope systems.

[0032] 2, the TEM 200 includes a source module 210 having an electron source 212, such as a field emission gun, that emits an electron beam 202 along an optical axis 204 toward a sample plane 252 where the sample is positioned. The electron beam 202 is focused by a gun lens 214 so that the electron beam 202 exhibits a beam crossover at a crossover plane 206. The source module 210 may additionally or alternatively be referred to as a source optical assembly 210.

[0033] The source module 210 additionally includes a source module aperture 218 configured to block a portion of the electron beam 202 for any of a variety of purposes. For example, in some examples, the source module 210 may include a monochromator (not shown in FIG. 2 ) that disperses the electron beam 202 to varying degrees based on electron energy, and the source module aperture may be configured to block all but a portion of the electron beam 202 that corresponds to a desired energy range. Additionally or alternatively, the source module aperture 218 may include and / or operate in conjunction with a beam deflector 216, as described in more detail below.

[0034] TEM 200 additionally includes a condenser module 230 downstream of source module 210 that shapes and / or otherwise configures electron beam 202 before reaching specimen plane 252. Condenser module 230 includes a first condenser lens 232, a second condenser lens 234, a third condenser lens 238, and a fourth condenser lens 242, as well as a first condenser aperture 236 and a second condenser aperture 240. Condenser module 230 may additionally or alternatively be referred to as a condenser optical assembly 230.

[0035] The first condenser lens 232, the second condenser lens 234, the third condenser lens 238, and / or the fourth condenser lens 242 can be used in conjunction with the first condenser aperture 236 and / or the second condenser aperture 240 to control various characteristics of the electron beam 202 directed at the sample, such as the diameter, collimation, and / or energy flux of the electron beam 202. For example, the relative strengths of the first condenser lens 232 and the second condenser lens 234 can determine the diameter and / or beam flux of the electron beam 202 in the plane of the first condenser aperture 236. The second condenser lens 234 and the third condenser lens 238 can be adjusted together to change the diameter and / or collimation of the electron beam 202 in the sample plane 252. The fourth condenser lens 242 can be used to change the magnification of the condenser module 230. The second condenser aperture 240 can be used to limit the illumination area at the sample plane 252.

[0036] TEM 200 further includes an objective module 250 downstream of condenser module 230. As shown in FIG. 2 , objective module 250 includes a first objective lens 254 positioned upstream of sample plane 252, a second objective lens 256 positioned downstream of sample plane 252, and an intermediate lens 258 positioned downstream of second objective lens 256. Objective module 250 may additionally or alternatively be referred to as an objective optical assembly 250.

[0037] A first objective lens 254 collimates the electron beam 202, while a second objective lens 256 focuses the electron beam 202 to a back focal plane 260. The objective module 250 also includes an objective aperture 262 positioned at the back focal plane 260. An intermediate lens 258 images the back focal plane 260 onto a diffraction plane 270 where a diffraction pattern 272 formed by the electron beam 202 can be recorded.

[0038] TEM 200 additionally includes a detector 280 positioned at a detector plane 282 for recording the diffraction pattern. In the example of FIG. 2, detector plane 282 is coplanar with diffraction plane 270.

[0039] As shown in FIG. 2 , when electron beam 202 encounters a sample at sample plane 252, the electron beam is modified by the sample, resulting in a conditioned electron beam 202′ downstream of sample plane 252. In particular, conditioned electron beam 202′ can include a portion of electron beam 202 that is modified through interaction with the sample, such as through a scattering interaction, such that conditioned electron beam 202′ contains information about the structure of the sample. Conditioned electron beam 202′ can also include a portion of electron beam 202 that passes through the sample substantially unchanged. In FIG. 2 , portions of electron beam 202 and / or conditioned electron beam 202′ that are modified through interaction with the sample are illustrated with dashed lines, while portions of electron beam 202 and / or conditioned electron beam 202′ that are not affected by the sample are shown with solid lines.

[0040] At any plane downstream of specimen plane 252, conditioned electron beam 202′ may be described as having a conditioned beam pattern. For example, in the example of FIG. 2, the rays of conditioned electron beam 202′ are focused at diffraction plane 270 such that the conditioned beam pattern at diffraction plane 270 includes and / or is diffraction pattern 272, which in the example of FIG. 2 may take the form of spaced beam spots. At other planes, the conditioned beam pattern may exhibit other shapes and / or forms, such as a ring, a disk, etc. In this manner, the conditioned beam pattern may be described as representing a cross-section of conditioned electron beam 202′ at the plane of interest.

[0041] In this disclosure, the term "diffraction plane" is intended to refer to a plane at which a portion of electron beam 202 passing through the sample is focused by one or more optical elements downstream of sample plane 252. Generally, TEM 200 may include multiple such planes that are conjugate to one another. With reference to FIG. 2 , for example, diffraction plane 270 is positioned downstream of back focal plane 260, but electron beam 202 and conditioned electron beam 202′ are also focused within back focal plane 260. Thus, back focal plane 260 can also be described as representing another diffraction plane of TEM 200. Generally, positioning detector 280 at any such diffraction plane can be used to record the diffraction pattern generated by the sample. However, in practice, it may be beneficial to position detector 280 at a diffraction plane (such as diffraction plane 270) where the diffraction pattern is magnified relative to that in back focal plane 260.

[0042] As introduced above, the TEM 200 includes a beam deflector 216 that can be used to selectively redirect the electron beam 202 away from the sample. As shown in Figure 2, the beam deflector 216 is positioned in a deflector plane 208 that is positioned within the source module 210. However, this is not required, and it is within the scope of the present disclosure that the deflector plane 208 may be located at a different location, such as a location away from (e.g., downstream of) the source module 210, and that the deflector plane 208 need not be the same as or adjacent to the crossover plane 206.

[0043] In some examples, the beam deflector 216 may be used to direct the electron beam 202 away from the sample until an image (e.g., a diffraction pattern) is recorded to protect the sample from damage by the electron beam 202. In this manner, the beam deflector 216 may be considered to represent a shutter mechanism that may be used to define, at least in part, the exposure time that the electron beam 202 is directed at the sample.

[0044] Additionally or alternatively, the beam deflector 216 may be configured to direct the electron beam 202 toward the sample in the form of short pulses, such that the sample is excited by the electron beam 202 for precisely controlled time intervals. In this manner, the beam deflector 216 may enable time-resolved analysis of the sample, in which the duration of the electron beam pulse can be varied to study the effects of varying the degree of sample excitation. As a more specific example, the TEM 200 may be used to perform pump-probe microscopy studies, which utilize linear optical imaging techniques for sample characterization and analysis. Additionally or alternatively, the beam deflector 216 may allow a user to vary the balance between time resolution (generally corresponding to shorter beam pulses) and signal intensity (generally corresponding to longer beam pulses).

[0045] 2, the beam deflector 216 may generally be configured to redirect the electron beam 202 to provide a deflected beam 203 downstream of the beam deflector 216, which may then be blocked by a blanking structure. In the example of FIG. 2, the blanking structure is a source module aperture 218. However, this is not necessary in all examples, and it is within the scope of the present disclosure that the beam deflector 216 may selectively direct the deflected beam 203 to any other suitable structure, such as a first condenser aperture 236 or a second condenser aperture 240.

[0046] The beam deflector 216 can assume any of a variety of forms. For example, the beam deflector 216 may include an electrostatic beam deflector in which a voltage is selectively applied to opposing electrodes to selectively redirect the electron beam 202 into the blanking structure, and / or may be an electrostatic beam deflector. As a more specific example, the electrostatic beam deflector may include rod-shaped electrodes positioned on either side of the optical axis 204, one of which is maintained at ground potential and the other of which is selectively placed at a deflection potential. When a substantial potential difference is introduced between the electrodes, the resulting electric field can redirect the trajectory of the electron beam 202 towards and / or into the blanking structure.

[0047] Additionally or alternatively, the beam deflector 216 may include and / or be a magnetic beam deflector in which a magnetic field is selectively generated (e.g., via an electric current) to deflect the electron beam 202.

[0048] Electrostatic beam deflectors can enable faster switching between blanked and unblanked states than magnetic beam deflectors. This can be particularly beneficial in the context of time-resolved studies with exposure periods on the order of nanoseconds. For example, in the case of magnetic beam deflectors, beam deflection can be achieved by generating a transverse magnetic field using a magnetic material. However, the slow settling time of magnetic domains in magnetic materials can limit the speed at which a magnetic beam deflector can transition between blanked and unblanked states. In addition, such magnetic materials can be susceptible to magnetic hysteresis effects, which introduce a residual magnetic field that is variable with each blanking-unblanking cycle. In contrast, electrostatic beam deflectors can be operated between blanked and unblanked states faster than magnetic beam deflectors and are less susceptible to magnetic hysteresis effects.

[0049] The beam deflector 216 may be incorporated into the TEM 200 in any suitable manner. For example, one or more components of the beam deflector 216 may be coupled to and / or supported by structures found in conventional TEM systems, such as a variable aperture mechanism. In other examples, the TEM 200 may include specialized structures for maintaining the beam deflector 216 in the proper position relative to the optical axis 204.

[0050] In this disclosure, two or more planes within and / or associated with a CPM system (such as TEM 200) may be described as being conjugate to one another when each point in one such plane is imaged onto a corresponding point in another such plane. For example, with reference to Figure 2, deflector plane 208, back focal plane 260, and diffraction plane 270 may all be described as being conjugate to one another.

[0051] As described in more detail below, configuring the TEM 200 so that the deflector plane 208 is conjugate to the diffraction plane 270 and / or the detector plane 282 can benefit the performance of the beam deflector 216. In particular, in such a configuration, the beam deflector 216 can induce a tilt of the electron beam 202 at a pivot plane that is conjugate to the detector plane 282. Thus, in such a configuration, the stationary point at which the electron beam 202 is deflected by the beam deflector 216 appears stationary at the detector plane 282, and the beam deflector 216 transitions between blanked and unblanked states. In this disclosure, such a configuration may generally be referred to as a conjugate blanking configuration.

[0052] 3A-3C are schematic diagrams of ray paths of an electron beam 302 traversing a TEM 300, which may share any suitable components, attributes, etc., with the TEM 200 of FIG. 2 and / or the CPM system 100 of FIG. 1. As described in more detail below, FIGS. 3A-3C illustrate one example of a sequence of operations that can bring the TEM 300 to a conjugate blanking configuration in accordance with the present disclosure. As described in more detail below, FIG. 3A may be described as representing an initial configuration of the TEM 300, FIG. 3B may be described as representing an intermediate configuration of the TEM 300, and FIG. 3C may be described as representing a conjugate blanking configuration of the TEM 300. However, it should be understood that the configurations illustrated in FIGS. 3A-3C represent non-exclusive examples of sequences of operations in accordance with the present disclosure. For example, as discussed in more detail below, another sequence of operations in accordance with the present disclosure can begin from an initial configuration other than that illustrated by FIG. 3A.

[0053] 3A-3C, the TEM 300 includes an electron source 310 that emits an electron beam 302 along an optical axis 301, a first optical element 312 (e.g., a lens), and a beam deflector 314 positioned at a deflector plane 332 downstream of the first optical element 312. The TEM 300 additionally includes a second optical element 316 (e.g., a lens) downstream of the deflector plane 332 and a third optical element 318 (e.g., a lens) downstream of the second optical element 316. The electron beam 302 is incident on a sample positioned at a sample plane 338, and a detector 322 positioned at a detector plane 324 records a modified beam pattern (e.g., a diffraction pattern) formed by the electron beam 302 downstream of the sample plane 338. A fourth optical element 320 (eg, a lens) is positioned between the sample plane 338 and the detector plane 324 to, for example, focus the electron beam 302 to form a diffraction pattern at a diffraction plane 340 .

[0054] For simplicity, Figures 3A-3C illustrate the trajectory of the electron beam 302 as shaped and / or guided by the optical elements of the TEM 300 without showing diffraction effects that may be introduced when a sample is positioned at the sample plane 338. However, it should be understood that the features and characteristics described herein with reference to Figures 3A-3C may also relate to instances in which the electron beam 302 is diffracted by a sample positioned at the sample plane 338. Accordingly, the descriptions of methods and / or procedures presented with reference to Figures 3A-3C may relate to instances in which a sample is positioned at the sample plane 338, as well as instances in which the sample is removed from the sample plane 338.

[0055] Similarly, the diffraction plane 340 corresponds to the plane in which the electron beam 302 forms a diffraction pattern when diffracted by the sample, although this plane may also be referred to as the diffraction plane 340 in instances in which the electron beam 302 is not diffracted by the sample. For example, as discussed in more detail below, the diffraction plane 340 may refer to the plane where a diffracted or non-diffracted electron beam exhibits a beam crossover and / or where a diffracted or non-diffracted electron beam is focused. In other words, the diffraction plane 340 refers to the plane in which a diffraction pattern is or will be formed when the electron beam 302 is diffracted by a sample, regardless of whether a sample is present. Thus, references to the diffraction plane 340 herein are not intended to imply that the corresponding electron beam is diffracted by a sample upstream of the diffraction plane 340.

[0056] First optical element 312, second optical element 316, third optical element 318, and / or fourth optical element 320 may each include and / or be any suitable optical element, such as the optical elements described above with reference to Figures 1 and 2. For example, first optical element 312 may represent, include, and / or be one or more lenses of a source module, such as gun lens 214 of Figure 2.

[0057] Additionally or alternatively, the second optical element 316 may represent, include, and / or be one or more lenses of a condenser module, such as the first condenser lens 232, the second condenser lens 234, the third condenser lens 238, and / or the fourth condenser lens 242 of FIG. 2.

[0058] Additionally or alternatively, third optical element 318 and fourth optical element 320 may each represent, include, and / or be one or more lenses of an objective module, such as first objective lens 254, second objective lens 256, and / or intermediate lens 258 of FIG. 2. As a more specific example, third optical element 318 may include and / or be an objective lens element, such as first objective lens 254 of FIG. 2, while fourth optical element 320 may include and / or be another objective lens element, such as second objective lens 256 of FIG. 2. In some examples, diffraction plane 340 may be a back focal plane associated with fourth optical element 320 or a plane conjugate to such a back focal plane.

[0059] 3A-3C additionally illustrate with dashed lines the ray paths of partially deflected beam 304, which represent a portion of electron beam 302 that has been partially redirected away from optical axis 301 and / or sample by beam deflector 314. Notably, a beam that is fully deflected by beam deflector 314 in a blanked state (e.g., deflected beam 203 in FIG. 2) does not reach sample plane 338 or diffraction plane 340; however, beam deflector 314 cannot instantaneously produce such a fully deflected beam. Instead, when beam deflector 314 transitions toward the blanked state, beam deflector 314 produces a continuous series of partially deflected beams that reach sample plane 338 and / or diffraction plane 340 along trajectories similar to those shown by dashed lines in FIGS. 3A-3C.

[0060] Any of the partially deflected beams 304 in FIGS. 3A-3C may be understood to represent any such beam trajectory associated with an intermediate state of the beam deflector 314 defined between an unblanked state and a fully blanked state. As used herein, the intermediate states of the beam deflector 314 may additionally or alternatively be referred to as a partially blanked state and / or a partially deflected state. In this manner, the beam deflector 314 may be described as transitioning between multiple (e.g., consecutive) intermediate and / or partially deflected states as the beam deflector 314 transitions between the unblanked and fully blanked states. Generally, each partially blanked state may generate a corresponding trajectory of the electron beam 304 downstream of the beam deflector 314 and / or a corresponding beam pattern at the detector plane 324. The electron beam 302 shown in solid lines in FIGS. 3A-3C may also be referred to as an unblanked electron beam 302 and / or an undeflected electron beam 302.

[0061] Thus, when used herein to characterize the state and / or configuration of the electron beam 302 and / or beam deflector 314, terms such as "partially deflected" and / or "partially blanked" do not necessarily refer to the state and / or configuration that the elements of the TEM 300 are intentionally brought to and / or maintained in. Rather, such terms may generally be understood to refer to any of a variety of intermediate states and / or configurations that are only temporarily recognized during operational use of the TEM, but that may still be illustrative in describing the operation of the beam deflector 314 between the blanked and unblanked states.

[0062] FIG. 3A illustrates a configuration of a TEM 300 in which operating the beam deflector 314 can cause a lateral movement of the electron beam 302 at the diffraction plane 340. FIG. 3A may be described, for example, as representing an example of an initial configuration of the TEM 300, before bringing the TEM into a conjugate blanking configuration. In particular, in the example of FIG. 3A, the diffraction plane 340 is coplanar with the detector plane 324 so that the diffraction pattern formed by the electron beam 302 is focused onto the detector 322. However, as can be seen by comparing the trajectories of the undeflected electron beam 302 and the partially deflected beam 304 at the detector plane 324, operating the beam deflector 314 between blanked and unblanked states moves the focused spot of the electron beam within the detector plane 324. As a result, when the beam deflector 314 transitions from an unblanked state to a blanked state, visible streaks may appear in the diffraction pattern recorded by the detector 322 before the electron beam 302 is completely blanked.

[0063] 4 illustrates one example of a streak 410 that may be formed in a diffraction plane (e.g., diffraction plane 340) and / or recorded by a detector (e.g., detector 322) when a beam deflector (e.g., beam deflector 314) transitions from an unblanked state to a fully blanked state. In particular, FIG. 4 illustrates an unblanked beam spot 402 and a partially blanked beam spot 404 connected by a streak 410 having a streak length 412. The unblanked beam spot 402 and the partially blanked beam spot 404 may be described as corresponding to the spots formed by the undeflected electron beam 302 and the partially deflected beam 304 of FIG. 3A, respectively, as recorded by detector 322. The streak 410 connecting the unblanked beam spot 402 and the partially blanked beam spot 404 can be described as representing the path traced by the focused electron beam at the detector plane as the beam deflector transitions towards a fully blanked state.

[0064] 4 illustrates one example of streaks that may be associated with a focused beam spot in a diffraction pattern, it should be understood that such description applies equally to features of the diffraction pattern and / or of focused and / or unfocused electron beams, such as rings, disks, etc. In such cases, streaking may additionally or alternatively manifest as blurring and / or elongation of such features.

[0065] As discussed above, the presence of such streaks 410 in the recorded diffraction pattern may be particularly undesirable in applications such as nanosecond-scale time-resolved pump-probe studies, where the time interval required to transition the beam deflector between an unblanked and fully blanked state is a significant fraction of the total exposure time. In contrast, the conjugate blanking configuration of the TEM described herein can result in a diffracted beam spot that is substantially stationary in the detector plane as the beam deflector transitions between an unblanked and fully blanked state. As a result, the form and / or details of the diffraction pattern can remain substantially unmodified accordingly by the process of blanking or unblanking the electron beam.

[0066] As used herein, when used to describe and / or characterize a beam spot or pattern in a given plane (e.g., in a diffraction plane and / or a detector plane), the term “substantially stationary” can refer to a beam spot or pattern that remains fixed in position relative to the plane and / or a beam spot or pattern that moves only slightly relative to the plane. For example, a beam spot or pattern may be described as “substantially stationary” during a process in which the orientation and / or shape of the beam spot or pattern shifts, e.g., via a change in size and / or rotational orientation of points remaining within the beam spot or pattern. Additionally or alternatively, a beam spot or pattern may be described as “substantially stationary” during a process in which the center point (e.g., center of gravity) of the beam spot or pattern shifts by a percentage of the maximum linear dimension of the beam spot or pattern that is less than 50% of the maximum linear dimension, less than 40% of the maximum linear dimension, less than 30% of the maximum linear dimension, less than 20% of the maximum linear dimension, and / or less than 10% of the maximum linear dimension.

[0067] 3A , the lateral offset of the focused spots of the undeflected electron beam 302 and the partially deflected beam 304 can be explained as being due to the axial separation of the deflector plane 332 from the crossover plane 330 at which the electron beam 302 is focused (e.g., by the first optical element 312). The crossover plane 330 can be explained as representing the first crossover plane 330, where the undeflected electron beam 302 and the partially deflected beam 304 are additionally focused to a crossover point at the second crossover plane 334.

[0068] In this disclosure, the term "crossover plane" may refer to any plane where the various rays characterizing a given beam (e.g., electron beam 304) are focused to a point and thus "cross over" one another. Thus, with reference to FIG. 3A, diffraction plane 340 may also be described as third crossover plane 340. It is within the scope of this disclosure that a given beam (e.g., electron beam) need not be focused exactly to a point at the crossover plane, and that the crossover plane may additionally or alternatively refer to a plane where the beam diameter reaches a non-zero minimum (e.g., due to optical aberrations).

[0069] In the example of Figure 3A, the third crossover plane 340 is coplanar with the detector plane 324. Thus, Figure 3A may be described as showing one example of an initial configuration in which the electron beam 302 is focused onto the detector 322. However, this is not required in all examples. It is additionally within the scope of this disclosure that the TEM 300 can be brought to the conjugate blanking configuration of Figure 3C from an initial configuration other than that shown in Figure 3A, such as an initial configuration in which the third crossover plane 340 is positioned upstream of the detector plane 324 or downstream of the detector plane 324.

[0070] 3A-3C can also be described with reference to a series of planes that are conjugate to deflector plane 332. For example, as shown in FIG. 3A, the illustrated configuration shows first conjugate deflector plane 336 and second conjugate deflector plane 342, each of which is conjugate to deflector plane 332.

[0071] Figure 3C illustrates the TEM 300 in a conjugate blanking configuration, while Figure 3B illustrates intermediate configurations of the TEM 300 that may be reached during one example of a method for bringing the TEM 300 into the conjugate blanking configuration of Figure 3C. In particular, relative to the configuration of Figure 3A, Figure 3B illustrates a configuration in which the fourth optical element 320 has been adjusted to move the second conjugate deflector plane 342 into axial alignment with the detector plane 324. For example, the fourth optical element 320 may include and / or be an objective lens element (e.g., the second objective lens 256 of Figure 2), and transitioning the TEM 300 from the configuration of Figure 3A to the configuration of Figure 3B may correspond to adjusting the objective lens element to shorten its focal length.

[0072] 3B , moving the second conjugate deflector plane 342 into axial alignment with the detector plane 324 can have the effect of shifting the diffraction plane 340 away from the detector plane 324, for example, to an axial position upstream of the detector plane 324. Thus, in this example, bringing the TEM 300 to the intermediate configuration of FIG. 3B can be described as having the effect of moving the focal plane of the electron beam 302 away from the detector plane 324, thereby defocusing the electron beam 302 at the detector plane 324. However, this is not necessary in all examples, and it is within the scope of this disclosure that bringing the TEM 300 to the intermediate configuration can include moving the diffraction plane 340 closer to the detector plane 324.

[0073] As used herein, when used to describe and / or characterize two or more entities (e.g., components, points, planes, etc.), the term "axial alignment" refers to a configuration in which the entities are located at a common axial location (e.g., relative to and / or along the optical axis 301).

[0074] 3B , an intermediate configuration of the TEM 300 corresponds to a configuration in which the undeflected electron beam 302 and the partially deflected beam 304 form overlapping spots at the detector plane 324. In this configuration, the detector plane 324 is conjugate to the deflector plane 332. Because the detector plane 324 is axially spaced from the diffraction plane 340, the spots corresponding to the undeflected electron beam 302 and the partially deflected beam 304 can be described as being unfocused spots. Because the spots corresponding to the undeflected electron beam 302 and the partially deflected beam 304 overlap at the detector plane 324, the location of the beam spots can remain substantially stationary when the beam deflector 314 transitions between an unblanked state and a fully blanked state.

[0075] Transitioning the TEM 300 from the intermediate configuration of Figure 3B to the conjugate blanking configuration of Figure 3C may correspond to focusing the undeflected electron beam 302 and the partially deflected beam 304 at the detector plane 324 while maintaining these focused spots in an overlapping configuration. In particular, transitioning the TEM 300 to the configuration of Figure 3C may be performed by adjusting the first optical element 312 to axially align the first crossover plane 330 with the deflector plane 332. As a more specific example, the first optical element 312 may include and / or be the gun lens 214 of Figure 2, and transitioning the TEM 300 to the configuration of Figure 3C may be performed by increasing the focal length of the first optical element 312. In such an example, the TEM 300 may be constrained to be used with such a gun lens setting during subsequent sample analysis, since the gun lens setting (e.g., excitation and / or focal length) at least partially determines the axial position of the first crossover plane 330. However, it should be understood that various other aspects of the electron beam 302 can be adjusted while the TEM 300 remains in the conjugate blanking configuration. For example, when the TEM 300 is in the conjugate blanking configuration, the width of the electron beam at the sample plane 338 may be adjusted to, for example, change the illuminated area of ​​the sample at the sample plane 338. Such adjustments may be made via adjustments of optical elements downstream of the deflector plane 332 and upstream of the sample plane 338, such as the second optical element 316 and / or the third optical element 318. As another example, when the TEM 300 is in a conjugate blanking configuration, the magnification of the diffraction pattern formed by the electron beam 302 at the detector plane 324 can be adjusted, for example, via adjustment of an optical element downstream of the sample plane 338 (e.g., the fourth optical element 320).

[0076] 3C , the deflector plane 332 is conjugate with each of the diffraction plane 340 and the detector plane 324, as well as with the second crossover plane 334. As a result, as the beam deflector 314 transitions from an unblanked state toward a fully blanked state, the electron beam 302 remains focused at one or more locations (e.g., a diffraction pattern) that remain substantially stationary at the detector plane 324. Once the beam deflector 314 reaches the fully blanked state, the electron beam 302 no longer reaches the detector plane 324, and the diffraction pattern substantially fades and / or disappears without exhibiting blurring and / or streaking.

[0077] 3A-3C illustrate a sequence of operations by which a TEM 300 is brought to a conjugate blanking configuration (FIG. 3C) from an initial state (FIG. 3A) in which the electron beam 302 is focused at the detector plane 324. In another example, a similar sequence of operations can be used to bring the TEM 300 to the conjugate blanking configuration of FIG. 3C when the electron beam 302 is not initially focused at the detector plane 324.

[0078] For example, the electron beam 302 may initially be underfocused such that the third crossover plane 340 is initially positioned downstream of the detector plane 324. In one such example, transitioning the TEM 300 to the conjugate blanking configuration may include first transitioning the TEM 300 to the intermediate configuration of FIG. 3B by axially aligning the second conjugate deflector plane 342 with the detector plane 324. Similar to the examples of FIGS. 3A and 3B, this may be achieved by shortening the focal length of the fourth optical element 320 and moving the second conjugate deflector plane 342 in an upstream direction. In some examples, this may have the effect of moving the third crossover plane 340 upstream past the axial position of the detector plane 324 such that the electron beam 302 continuously increases and decreases its focus at the detector plane 324 as the TEM 300 transitions to the intermediate configuration.

[0079] As another example, the electron beam 302 may initially be overfocused such that the third crossover plane 340 is initially positioned upstream of the detector plane 324. In one such example, transitioning the TEM 300 to the conjugate blanking configuration may again involve first transitioning the TEM 300 to the intermediate configuration of FIG. 3B by axially aligning the second conjugate deflector plane 342 with the detector plane 324. In this example, this may be achieved by increasing the focal length of the fourth optical element 320 and moving the second conjugate deflector plane 342 downstream.

[0080] However, the configuration in which the electron beam 302 is initially overfocused may correspond to a configuration in which the second conjugate deflector plane 342 is initially positioned upstream or downstream of the detector plane 324. Thus, axially aligning the second conjugate deflector plane 342 with the detector plane 324 can have the result of increasing and / or decreasing the degree of focusing of the electron beam 302 at the detector plane 324 while the TEM 300 transitions to the intermediate configuration.

[0081] Generally, when the TEM 300 is initially in a configuration in which the electron beam 302 is not focused at the detector plane 324, it may be unknown whether the electron beam 302 will be underfocused or overfocused relative to the detector plane 324. Therefore, it may be unknown whether the second conjugate deflector plane 342 will need to be moved upstream or downstream to axially align the second conjugate deflector plane 342 with the detector plane 324.

[0082] Thus, transitioning the TEM 300 from any initial configuration to an intermediate configuration may involve iteratively shifting the second conjugate deflector plane 342 in an upstream or downstream direction and measuring the effects of such shifts. For example, since the intermediate configuration corresponds to a configuration in which the undeflected electron beam 302 and the partially deflected beam 304 overlap at the detector plane 324, the intermediate configuration may be reached by iteratively shortening and / or minimizing the streak length between the undeflected electron beam 302 and the partially deflected beam 304 during operation of the beam deflector 314.

[0083] 3A-3C show a sequence of operations in which the TEM 300 is brought into a conjugate blanking configuration by first axially aligning the second conjugate deflector plane 342 with the detector plane 324, and then axially aligning the first crossover plane 330 with the deflector plane 332. Performing such adjustments in this order can ensure that the detector plane 324 remains conjugate with the deflector plane 332 while the electron beam 302 is focused onto the detector plane 324 using the first optical assembly 312.

[0084] However, this order is not required in all examples. For example, the TEM 300 can also be brought to a conjugate blanking configuration by iteratively adjusting an upstream optical element (e.g., the first optical element 312) positioned upstream of the deflector plane 332 to a selected setting, using a downstream optical element (e.g., the fourth optical element 320) positioned downstream of the deflector plane 332 to focus the electron beam 302 onto the detector plane 324, and measuring the streak length between the undeflected electron beam 302 and the partially deflected beam 304. In some examples, bringing the upstream optical element to a selected setting can include adjusting the focal length of the upstream optical element to adjust the defocus of the electron beam 302 at the deflector plane 324. Thus, repeating these steps with different selected settings (e.g., focal lengths) of the upstream optical element allows comparison between the streak lengths corresponding to such settings. The difference (e.g., sign and magnitude) between successively measured streak lengths may then be used to iteratively select subsequent settings of the upstream optics until the measured streak length is minimized with the electron beam 302 focused at the detector plane 324, at which point the TEM 300 may be understood to be in a conjugate blanking configuration. Such an iterative process may be performed manually and / or at least partially automatically.

[0085] Figures 5A and 5B represent example diffraction patterns of a gold sample recorded before (Figure 5A) and after (Figure 5B) bringing the TEM into the conjugate blanking configuration. That is, Figure 5A can be described as representing an example of a diffraction pattern 500 recorded at the diffraction plane 502 with a TEM in an initial configuration similar to that of Figure 3A, while Figure 5B can be described as representing an example of a corresponding diffraction pattern 500' recorded with the same TEM in the conjugate blanking configuration shown in Figure 3C.

[0086] In each of Figures 5A and 5B, a diffraction pattern is recorded using a detector (e.g., detector 322) during an exposure that is terminated by transitioning a beam deflector (e.g., beam deflector 314) to a fully blanked state. As shown in Figures 5A and 5B, diffraction pattern 500 obtained using a TEM without a conjugate blanking configuration exhibits significantly blurred and less well-resolved features than the corresponding diffraction pattern 500' obtained using a TEM with a conjugate blanking configuration. In particular, comparing Figures 5A and 5B, it can be seen that diffraction pattern 500 exhibits blurring along blur direction 504, thus making it more difficult to accurately measure the radius of each feature in diffraction pattern 500 than in the example of diffraction pattern 500'.

[0087] Figures 6A and 6B show additional examples of diffraction patterns of single-crystal gallium nitride recorded before (Figure 6A) and after (Figure 6B) bringing the TEM into the conjugate blanking configuration. That is, Figure 6A can be described as representing an example of a diffraction pattern 600 recorded at the diffraction plane 602 using a TEM in an initial configuration similar to that of Figure 3A, while Figure 6B can be described as representing an example of a corresponding diffraction pattern 600' recorded using the same TEM in the conjugate blanking configuration shown in Figure 3C. Figures 5A and 5B illustrate an example of a diffraction pattern including a series of diffraction rings, while Figures 6A and 6B illustrate an example of a diffraction pattern including spaced and localized diffraction spots.

[0088] In each of Figures 6A and 6B, a diffraction pattern is recorded using a detector (e.g., detector 314) during an exposure that is terminated by transitioning a beam deflector (e.g., beam deflector 322) to a fully blanked state. As shown in Figures 6A and 6B, diffraction pattern 600 obtained using a TEM without a conjugate blanking configuration exhibits significantly blurred and less well-resolved features than the corresponding diffraction pattern 600' obtained using a TEM with a conjugate blanking configuration. In particular, comparing Figures 6A and 6B, it can be seen that diffraction pattern 600 exhibits blurring along blur direction 604, thus making the position of each feature in diffraction pattern 600 more difficult to accurately measure than in the example of diffraction pattern 600'.

[0089] Exemplary Methods 7 is a flowchart illustrating an example method 700 of operating a CPM system, the CPM system including a beam deflector positioned at a deflector plane and configured to direct a charged particle beam toward a sample to generate a diffraction beam pattern at a diffraction plane. Method 700 may be implemented with any suitable CPM system. For example, the CPM system may include and / or be the CPM system 100 of FIG. 1, the TEM 200 of FIG. 2, and / or the TEM 300 of FIGS. 3A-3C, and / or any suitable portion thereof. The CPM system may additionally or alternatively include any suitable features and / or characteristics not specifically described herein.

[0090] Any of the system components discussed and / or described herein with reference to method 700 may be understood to represent and / or refer to similarly named components of CPM system 100, TEM 200, and / or TEM 300, and / or their functional equivalents. For example, the beam deflector described herein with reference to method 700 may represent deflector 112 of FIG. 1, beam deflector 216 of FIG. 2, and / or beam deflector 314 of FIG. 3A-3C. As such, method 700 may be understood in the context of the above description of CPM system 100, TEM 200, and / or TEM 300, and vice versa. However, this is not required, and it is additionally within the scope of this disclosure that method 700 may be practiced with any suitable components.

[0091] 7, method 700 includes adjusting one or more optical elements of a CPM system so that a deflector plane is conjugate with a diffraction plane, at 710. Method 700 additionally includes recording the diffracted beam pattern with a detector positioned at the diffraction plane, at 730.

[0092] As described herein, adjusting the optical element at 710 can include adjusting the position (e.g., axial position) of the diffraction plane to axially align the diffraction plane with the detector at 712. For example, the CPM system can include a first optical assembly positioned upstream of the deflector plane and a second optical assembly positioned downstream of the deflector plane, and adjusting the position of the diffraction plane at 712 can include adjusting one or more optical elements of the second optical assembly at 714. In particular, adjusting the position of the diffraction plane at 712 can include adjusting the optical elements of the second optical assembly to shift the position of the diffraction plane axially (e.g., along the optical axis 301 of FIGS. 3A-3C ). With reference to the TEM 200 of FIG. 2 , for example, the first optical assembly can include one or more components of the source module 210 upstream of the beam deflector 216, and / or the second optical assembly can include one or more components of the condenser module 230 and / or the objective module 250. Thus, as a more specific example, adjusting the optical elements of the second optical assembly at 714 may include adjusting the second objective lens 256 and / or the intermediate lens 258 to shift the axial location of the diffraction plane, as discussed above.

[0093] 3A-3C , the first optical assembly may include and / or be the first optical element 312, and the second optical assembly may include and / or be any of the second optical element 316, the third optical element 318, and / or the fourth optical element 320. Thus, as a more specific example, adjusting the optical elements of the second optical assembly at 714 may include adjusting the fourth optical element 320 to shift the axial location of the diffraction plane, as discussed above.

[0094] As discussed above, a diffraction plane may refer to a plane in which a diffraction pattern is formed when a charged particle beam passes through a sample, and this plane may still be referred to as a diffraction plane even when no sample and / or diffraction pattern is present.

[0095] 7, adjusting the optical elements of the second optical assembly at 714 can include adjusting a focal length of the elements of the second optical assembly at 716. For example, the second optical assembly can include an objective lens, such as second objective lens 256 and / or intermediate lens 258 of FIG. 2, and adjusting the position of the diffraction plane at 712 can include adjusting the focal length of the objective lens to axially align the diffraction plane with the detector.

[0096] 7, adjusting the optical elements at 710 can additionally include adjusting one or more optical elements of a first optical assembly to axially align a crossover plane of the charged particle beam with the detector at 720. In particular, in some examples, adjusting the optical elements of the first optical assembly at 720 can include adjusting a focal length associated with the first optical assembly at 722, as shown in FIG.

[0097] As a more specific example, with reference to TEM 200 of Figure 2, adjusting the optical elements of the first optical assembly at 720 can include adjusting gun lens 214, for example, to change the focal length of gun lens 214. Additionally or alternatively, and with reference to CPM system 300 of Figures 3A-3C, adjusting the optical elements of the first optical assembly at 720 can include adjusting first optical element 312, for example, by adjusting its focal length.

[0098] In some examples, the focal length of the first optical assembly adjusted during the adjustment at 722 may be referred to as the first focal length, and the focal length of the second optical assembly adjusted during the adjustment at 716 may be referred to as the second focal length.

[0099] Adjusting the first focal length at 722 and / or adjusting the second focal length at 716 may each be performed in any suitable manner. For example, the optical elements adjusted during adjusting the optical elements of the first optical assembly at 720 and / or adjusting the optical elements of the second optical assembly at 714 may include and / or be electro-optic lens elements, and adjusting the focal length at 716 and / or adjusting the focal length at 722 may include adjusting an excitation voltage applied to such lens elements. In some examples, this may be performed at least in part using a controller, such as controller 150 of FIG. 1 .

[0100] Adjusting the optical elements of the first optical assembly at 720 and / or adjusting the first focal length at 722 can include adjusting a crossover plane of the charged particle beam (e.g., first crossover plane 330 of FIGS. 3A-3C ) to be axially aligned with a deflector plane. Additionally or alternatively, adjusting the optical elements of the second optical assembly at 714 and / or adjusting the second focal length at 716 can include adjusting a conjugate deflector plane (e.g., second conjugate deflector plane 342 of FIGS. 3A-3C ) to be axially aligned with a detector plane, as described herein.

[0101] In some examples, adjusting the optical elements of the first optical assembly at 720 is performed subsequent to adjusting the optical elements of the second optical assembly at 714. In some such examples, adjusting the optical elements of the second optical assembly at 714 is performed when the CPM system is in an initial configuration in which the charged particle beam is focused at the detector plane. In such examples, adjusting the optical elements of the second optical assembly at 714 may include adjusting the charged particle beam so that it is unfocused (and / or gradually unfocused) at the detector. However, this is not required in all examples. For example, it is within the scope of the present disclosure that adjusting the optical elements of the second optical assembly at 714 may be performed when the CPM system is in an initial configuration in which the charged particle beam is underfocused or overfocused relative to the detector plane.

[0102] Generally, as discussed above, it may be initially unknown whether the charged particle beam will be underfocused or overfocused in the initial configuration of the CPM system. Accordingly, adjusting the optical elements of the second optical assembly at 714 may include iteratively adjusting the optical elements, measuring the effect of each adjustment, and making subsequent adjustments based on the measured effect.

[0103] For example, in any given configuration of the second optical assembly, method 700 may include operating a beam deflector between an unblanked state and a blanked state (e.g., a partially blanked state or a fully blanked state) and recording an initial streak length formed by the charged particle beam at the detector plane when the beam deflector is operated between the unblanked state and the blanked state. Recording the streak length may be performed in any suitable manner, such as described herein with reference to FIG.

[0104] Adjusting the optical elements of the second optical assembly at 714 may then include adjusting the focal length of the second optical assembly in a first direction, for example, to move a conjugate deflector plane in an upstream direction, and recording an updated streak length as the beam deflector is operated between the unblanked and blanked states. If the updated streak length is less than the initial streak length, adjusting the optical elements of the second optical assembly at 714 may be performed to move the conjugate deflector plane further in the first direction and measure a new, updated streak length. If the updated streak length is greater than the initial streak length, adjusting the optical elements of the second optical assembly at 714 may be performed to move the conjugate deflector plane in a second direction opposite the first direction and measure a new, updated streak length. Such operations may be performed iteratively until the measured streak length is minimized, which may indicate that the conjugate deflector plane is axially aligned with the detector plane.

[0105] In a configuration in which the conjugate deflector plane is axially aligned with the detector plane, the charged particle beam can form a defocused beam pattern at the deflector plane. The method 700 can then include performing 720 adjusting the optical elements of the first optical assembly in a manner such that the beam pattern regains and / or increases focus at the detector.

[0106] The beam pattern at the detector can refer to any suitable form and / or pattern of the charged particle beam at the detector plane, regardless of whether the charged particle beam is modified by the sample at the sample plane. For example, the beam pattern at the detector may include a modified beam pattern and / or may be a modulated beam pattern, which may refer to any suitable portion and / or feature of the charged particle beam downstream of the sample that is deflected (e.g., diffracted) and / or otherwise altered through interaction with the sample, such as modified electron beam 202′ in FIG. 2. Additionally or alternatively, the beam pattern at the detector may include and / or be any suitable portion and / or feature of the charged particle beam that is substantially unmodified by interaction with the sample.

[0107] In the present disclosure, the degree of focus and / or its characteristics of a beam pattern in a given plane may be characterized by a characteristic (e.g., maximum) diameter of the beam pattern in the given plane. In particular, the degree of focus may be described as increasing and / or improving when such characteristic diameter decreases.

[0108] Recording the diffraction beam pattern in 730 may be performed in any suitable manner. For example, the diffraction beam pattern recorded by the detector may include and / or be any suitable pattern, such as a diffraction pattern (e.g., a diffractogram) including diffraction spots, rings, disks, etc. The detector may include and / or be any suitable detector, such as TEM camera 130 of FIG. 1 , detector 280 of FIG. 2 , and / or detector 322 of FIGS. 3A-3C . Recording the diffraction beam pattern in 730 may be performed with the sample positioned at a sample plane such that the sample modulates the charged particle beam to generate the diffraction beam pattern. However, as discussed above, other aspects of method 700 may be performed when the sample is positioned at the sample plane or when the sample has been removed from the sample plane.

[0109] 8 is a flowchart illustrating an additional example of a method 800 for operating a CPM system according to the present disclosure. Method 800 may be implemented in conjunction with any suitable CPM system. For example, the CPM system may include and / or be CPM system 100 of FIG. 1, TEM 200 of FIG. 2, and / or TEM 300 of FIGS. 3A-3C, and / or any suitable portions thereof. The CPM system may additionally or alternatively include any suitable features and / or characteristics not specifically described herein.

[0110] Any of the system components discussed and / or described herein with reference to method 800 may be understood to represent and / or refer to similarly named components of CPM system 100, TEM 200, and / or TEM 300, and / or their functional equivalents. For example, the beam deflector described herein with reference to method 800 may represent deflector 112 of FIG. 1, beam deflector 216 of FIG. 2, and / or beam deflector 314 of FIG. 3A-3C. As such, method 800 may be understood in the context of the above description of CPM system 100, TEM 200, and / or TEM 300, and vice versa. However, this is not required, and it is additionally within the scope of this disclosure that method 800 may be practiced with any suitable components.

[0111] Additionally, any of the methods disclosed herein with reference to Figure 8 may also be described as including and / or representing any of the method steps disclosed herein with reference to Figure 7, and vice versa. For example, method 700 and method 800 may include steps that are performed in a substantially similar manner and / or that produce a similar effect.

[0112] As shown in FIG. 8 , method 800 includes directing 810 a charged particle beam toward a sample, which adjusts the charged particle beam to create a beam pattern downstream of the sample. Method 800 additionally includes transitioning a beam blanker of a CPM system between an unblanked state and a blanked state at 840 and recording the beam pattern with a detector at 850. When the beam blanker is in the unblanked state, the charged particle beam can reach the sample and create a beam pattern downstream of the sample. When the beam blanker is in the blanked state, the beam blanker directs the charged particle beam away from the sample, for example, in a manner as discussed above with reference to FIG. 2 .

[0113] A beam blanker may also be referred to as a beam deflector. Examples of beam blankers that may be used with method 800 include deflector 112 of Figure 1, beam deflector 216 of Figure 2, and / or beam deflector 314 of Figures 3A-3C. During recording of the beam pattern at least at 850, the beam blanker is positioned at a deflector plane and a detector is positioned at a detector plane that is conjugate to the deflector plane.

[0114] During recording of the beam pattern at least at 850, the beam pattern may include one or more beam pattern features that are focused in the detector plane. Such beam pattern features may include and / or may be spots, rings, disks, etc. Referring to FIG. 2, for example, the beam pattern features may include and / or may be diffraction pattern 272 formed by electron beam 202 and conditioned electron beam 202′ at detector plane 282.

[0115] Method 800 may be implemented such that beam pattern features are substantially stationary in the detector plane as the beam blanker transitions between the unblanked and blanked states. Thus, as discussed above, transitioning the beam blanker between the unblanked and blanked states may allow the beam pattern to impinge on the detector without resulting in the streaking discussed above in the context of FIG. 4 and / or the blurring of features shown in FIG. 5A . As discussed above, this may be particularly beneficial in instances where the beam blanker is used to perform ultrafast time-resolved studies of a sample, e.g., by exposing the sample to an electron beam for a duration on the order of nanoseconds. As a more specific example, method 800 may be implemented using an electrostatic beam blanker and / or such that transitioning the beam blanker in 840 is performed for a period of less than 10 nanoseconds (ns).

[0116] 8, the method 800 may include, at 820, configuring the CPM system in a conjugate blanking configuration, which may result in the beam pattern features remaining substantially stationary, as discussed above. When the CPM system is in the conjugate blanking configuration, the deflector plane is conjugate with the detector plane, and the crossover of the charged particle beam (e.g., its focal plane) is positioned at the deflector plane (e.g., axially aligned with the deflector plane).

[0117] In some examples, configuring the CPM system at 820 may be performed at least in part subsequent to directing the charged particle beam toward the sample at 810. In some such examples, configuring the CPM system at 820 may include observing, measuring, and / or recording a portion of the charged particle beam at a deflector plane that is modified (e.g., diffracted) by the sample. Additionally or alternatively, configuring the CPM system at 820 may be performed at least in part prior to directing the charged particle beam toward the sample at 810. In some such examples, configuring the CPM system at 820 may include observing, measuring, and / or recording a portion of the charged particle beam at a deflector plane that is not modified by and / or that did not interact with the sample. As a more specific example, configuring the CPM system at 820 may be performed with the sample removed from the beam path of the charged particle beam.

[0118] Configuring the CPM system at 820 may be implemented in any of a variety of manners. For example, as shown in FIG. 8 , configuring the CPM system at 820 may include bringing the CPM system to an intermediate configuration at 822, where the detector plane is conjugate to the deflector plane. Configuring the CPM system at 820 may additionally include bringing the CPM system to a conjugate blanking configuration at 832, following bringing the CPM system to the intermediate configuration at 822. With reference to FIGS. 3A-3C , FIG. 3B may be described as illustrating an example of an intermediate configuration, while FIG. 3C may be described as illustrating an example of a conjugate blanking configuration.

[0119] 8, bringing the CPM system to the intermediate configuration at 822 includes shifting a conjugate deflector plane (e.g., second conjugate deflector plane 342 in FIGS. 3A-3C ) into axial alignment with the detector plane at 824. In some examples, bringing the CPM system to the intermediate configuration at 822 and / or shifting the conjugate deflector plane at 824 may include adjusting the focal length of one or more optical elements downstream of the deflector plane, for example, in any suitable manner as discussed above.

[0120] Bringing the CPM system to the intermediate configuration in 822 can be performed in any suitable manner to ensure that the detector plane is conjugate with the deflector plane. For example, as discussed above in the context of FIG. 3B , the intermediate configuration may represent a configuration in which the beam spot (e.g., the beam spot of the non-diffracting charged particle beam and / or the beam spot of the diffracting beam pattern feature) at the detector plane is unfocused but substantially stationary when the beam blanker transitions between an unblanked state and a blanked state. Thus, bringing the CPM system to the intermediate configuration in 822 may include the CPM system defocusing the beam spot (or adjusting the focus of the beam spot) during operation of the beam blanker until the CPM system reaches a configuration in which the beam spot is substantially stationary.

[0121] 8 , bringing the CPM system to the intermediate configuration at 822 may include adjusting a beam blanker between an unblanked state and a blanked state at 828 to move a test beam pattern feature at the detector plane. For example, adjusting the beam blanker at 828 may include changing a deflection of the charged particle beam caused by the beam blanker, e.g., by changing and / or adjusting a voltage applied to the electrostatic beam blanker. The test beam pattern feature may include and / or be any suitable feature (e.g., spot, ring, disk, etc.) and / or combination of features of a beam spot and / or pattern.

[0122] Adjusting the beam blanker in 828 may be performed repeatedly (e.g., periodically) and may include adjusting the beam blanker to reach an unblanked state and / or a (fully) blanked state. Additionally or alternatively, adjusting the beam blanker in 828 may be performed such that the beam blanker transitions between multiple states between (but not including) the unblanked state and / or the fully blanked state.

[0123] Bringing the CPM system to the intermediate configuration at 822 may also include adjusting one or more optical elements downstream of the deflector plane at 830 and fixing the test beam pattern feature in a substantially stationary position within the deflector plane while adjusting the beam blanker at 828.

[0124] Adjusting the beam blanker at 828 and adjusting the optical element at 830 may be performed at least partially sequentially and / or at least partially simultaneously. For example, bringing the CPM system to the intermediate configuration at 822 may include adjusting the beam blanker between an unblanked state and a blanked state and determining the extent to which a test beam pattern feature shifts at a detector plane during such adjustment (e.g., by observing the test beam pattern feature with a detector). The extent of such shifting may be qualitatively and / or quantitatively characterized, for example, via manual observation and / or measurement of a streak length associated with the streak (e.g., streak length 412 in FIG. 4 ). Bringing the CPM system to the intermediate configuration at 822 may then include incrementally adjusting one or more optical elements to axially shift a conjugate deflector plane (e.g., second conjugate deflector plane 342 in FIGS. 3A-3C ) and repeating adjusting the beam blanker at 828 to determine whether the CPM system has reached the intermediate configuration. In particular, the CPM system may be understood to be in an intermediate configuration when the test beam pattern feature is observed to be substantially stationary in the detector plane while adjusting the beam blanker at 828.

[0125] With the CPM system in the intermediate configuration, bringing the CPM system to the conjugate blanking configuration at 832 may include focusing the beam pattern at 834 to the detector plane, such as in the manner described above with reference to FIG. 3C . For example, focusing the beam pattern at 834 may include adjusting one or more optical elements upstream of the deflector plane at 836 to bring the crossover plane of the charged particle beam to the detector plane. As a more specific example, adjusting the optical element at 836 may include adjusting the focal length of a source module optical element, such as a gun lens, such that the diffraction plane of the charged particle beam is axially aligned with the detector plane. Such a configuration may be achieved, for example, when the focal length of the gun lens is such that the focal plane of the charged particle beam (e.g., first crossover plane 330 in FIGS. 3A-3C ) is axially aligned with the deflector plane. Since the detector plane is conjugate to the deflector plane in the intermediate configuration, creating a beam crossover at the deflector plane results in a corresponding crossover being formed at the detector plane, which in turn can correspond to the diffraction plane of the charged particle beam downstream of the specimen, so that in the conjugate blanking configuration the diffraction pattern is focused at the detector plane.

[0126] Any aspects of method 700 and / or method 800 may be performed at least partially automatically, e.g., via a controller of the CPM system (e.g., controller 150 of FIG. 1 ). For example, such a controller may be programmed and / or configured to receive an image and / or corresponding signal from a detector and determine, for example, whether the detector plane is conjugate with a deflector plane and / or axially aligned with a crossover plane as described herein. Additionally or alternatively, the controller may be programmed and / or configured to control one or more optical elements of the CPM system, for example, to vary the focal length of one or more electro-optic lenses and / or to selectively deflect the charged particle beam using a beam deflector. Additionally or alternatively, the controller may be programmed and / or configured to perform various method steps that are iteratively repeated to achieve a desired configuration, such as adjusting a beam blanker at 828 and / or adjusting an optical element at 830.

[0127] 9 and the following discussion are intended to provide a brief, general description of an exemplary computing environment in which the disclosed techniques may be implemented. In particular, some or all portions of this computing environment may be used in conjunction with the methods and apparatus described above, for example, to configure a CPM system in a conjugate blanking configuration, focus a charged particle beam onto a sample, record a diffraction pattern, and / or perform any portion of the methods disclosed above.

[0128] Although not required, the disclosed technology will be described in the general context of computer-executable instructions, such as program modules, being executed by a personal computer (PC). Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Moreover, the disclosed technology may be implemented using other computer system configurations, including handheld devices, tablets, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, etc. The disclosed technology may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. In some cases, such processing is provided in a CPM. The disclosed system may be responsible for controlling image acquisition and providing a user interface, as well as acting as an image processor.

[0129] 9, an exemplary system for implementing the disclosed technology includes a general-purpose computing device in the form of an exemplary conventional PC 900 including one or more processing units 902, a system memory 904, and a system bus 906 that couples various system components including the system memory 904 to the one or more processing units 902. The system bus 906 can be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The exemplary system memory 904 includes read-only memory (ROM) 908 and random-access memory (RAM) 910. A basic input / output system (BIOS) 912, containing the basic routines that help to transfer information between elements within the PC 900, is stored in ROM 908.

[0130] The exemplary PC 900 further includes one or more storage devices 930, such as a hard disk drive for reading from and writing to a hard disk, a magnetic disk drive for reading from and writing to a removable magnetic disk, and an optical disk drive for reading from and writing to a removable optical disk (such as a CD-ROM or other optical media). Such storage devices may be connected to the system bus 906 by a hard disk drive interface, a magnetic disk drive interface, and an optical drive interface, respectively. The drives and associated computer-readable media provide non-volatile storage of computer-readable instructions, data structures, program modules, and other data for the PC 900. Other types of computer-readable media capable of storing data accessible by a PC, such as magnetic cassettes, flash memory cards, solid-state drives, digital video disks, CDs, DVDs, RAM, ROM, etc., may also be used in the exemplary operating environment.

[0131] A number of program modules may be stored on storage device 930, including an operating system, multiple operating systems, virtual operating systems, one or more application programs, other program modules, and program data. In some examples, one or more aspects of the methods disclosed herein may be programmed, implemented, encoded, trained, and / or possibly transferred to a program module via machine learning, neural networks, artificial intelligence, etc.

[0132] The exemplary PC 900 may include various devices configured for a user interface. For example, a user may input commands and information into the PC 900 through one or more input devices 940, such as a keyboard and a pointing device such as a mouse. For example, a user may input commands to initiate image acquisition and / or to initiate one or more methods disclosed herein. Other input devices may include a digital camera, microphone, joystick, gamepad, buttons, dials, satellite receiver, scanner, etc. In some examples, several such input devices may be combined into a single user interface device, such as may be commonly used in conjunction with CPM systems. These and other input devices are often connected to one or more processing units 902 through a serial port interface coupled to the system bus 906, but may also be connected by other interfaces, such as a parallel port, game port, Universal Serial Bus (USB), or wired or wireless network connection. A monitor 946 or other type of display device may also be connected to the system bus 906 via an interface, such as a video adapter, to display one or more images of the sample or specimen, for example, before, after, and / or during performance of one or more of the methods disclosed herein. The monitor 946 may also be used to select sections for processing, such as correlation, feature identification, and preview area selection or other image selection, or particular image registration and alignment procedures. Other peripheral output devices, such as speakers and a printer (not shown), may be included.

[0133] The PC 900 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 960. In some embodiments, one or more network or communication connections 950 are included. The remote computer 960 may be another PC, a server, a router, a network PC, a peer device, or other common network node, and typically includes many or all of the elements described above in connection with the PC 900, although only the memory storage device 862 is illustrated in FIG. 9 . The personal computer 900 and / or the remote computer 960 may be connected to local area networks (LANs) and wide area networks (WANs). Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and the Internet.

[0134] 12, memory 990 (or portions of this or other memory) can store processor-executable instructions for controlling beam focus, controlling beam deflectors, pattern recognition and analysis (e.g., to detect and / or characterize the movement of beam features at a detector plane), etc. For example, such processor-executable instructions, when executed by a processor system, can cause PC 900 and / or another component (e.g., any suitable component of CPM system 100 of FIG. 1, TEM 200 of FIG. 2, and / or TEM 300 of FIGS. 3A-3C) to perform any of the methods disclosed herein. In some examples, the processor-executable instructions can generate a display image (e.g., of a recorded diffraction pattern) showing the processing of a preview image and / or the acquisition of additional images.

[0135] General Considerations As used in this application and the claims, the singular forms "a," "an," and "the" include the plural forms unless the content clearly dictates otherwise. Additionally, the term "includes" means "having, comprising." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0136] Unless otherwise specified, as used herein, the term "substantially" refers to the recited value and / or characteristic, as well as any value and / or characteristic that is at least 75% of the recited value and / or characteristic. Equivalently, the term "substantially" refers to the recited value and / or characteristic, as well as any value and / or characteristic that differs from the recited value and / or characteristic by no more than 25%. For example, "substantially equal" refers to amounts that are exactly equal and amounts that differ from each other by no more than 25%.

[0137] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with one another. The disclosed systems, methods, and devices are not limited to any specific aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require that any one or more specific advantages be present or problems be solved. While any theory of operation is provided for ease of explanation, the disclosed systems, methods, and devices are not limited to such theory of operation.

[0138] Although some operations of the disclosed methods are described in a particular sequential order for convenient presentation, it should be understood that the format of the specification encompasses reordering unless a specific ordering is required by specific language set forth below. For example, operations described in sequence may in some cases be reordered or performed simultaneously. Moreover, for the sake of simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and apparatuses can be used in conjunction with other systems, methods, and apparatuses. Additionally, the specification may use terms such as "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of actual operations that take place. The actual operations corresponding to these terms will vary depending on the particular implementation and are readily discernible by those skilled in the art.

[0139] In some instances, values, procedures, etc. may be characterized by qualifying terms such as "lowest," "best," "minimum," "extreme," etc. It is to be understood that such descriptions are intended to indicate that choices can be made from among many functional alternatives used, and that such choices are not necessarily better, lesser, or otherwise preferred relative to other choices.

[0140] The innovation may be described in the general context of computer-executable instructions, such as instructions included in a program module, being executed on a target real or virtual processor in a computing system. Generally, program modules or components include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or divided among program modules as desired in various instances. Computer-executable instructions for program modules may be executed in a local computing system or in a distributed computing system. Generally, a computing system or computing device can be local or distributed and can include any combination of dedicated and / or general-purpose hardware and software that implements the functionality described herein; examples of computing systems or computing devices include personal computers, handheld devices, tablets, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, virtual machines, containerized applications, Kubernetes clusters, etc.

[0141] In various examples described herein, a module (e.g., a component or engine) can be "programmed" / "coded" to perform particular operations or provide particular functionality, indicating that computer-executable instructions for the module can be executed to perform such operations, cause such operations to be performed, or otherwise provide such functionality. Functionality described in terms of a software component, module, or engine can be performed as a separate software unit (e.g., a program, function, class method), but need not be implemented as a separate unit. That is, functionality can be incorporated into a larger or more general program, such as one or more lines of code within the larger or more general program.

[0142] The described algorithms may be embodied as software or firmware instructions executed by, for example, a digital computer. For example, any of the disclosed methods may be implemented by one or more computers or other computing hardware that are part of a microscopy tool. The computer may be a computer system including one or more processors (processing elements) and tangible, non-transitory computer-readable media (e.g., one or more optical media disks, volatile memory elements (such as DRAM or SRAM), or non-volatile memory or storage elements (such as hard drives, NVRAM, and solid-state drives (e.g., flash drives)). The one or more processors may execute computer-executable instructions stored on one or more of the tangible, non-transitory computer-readable media, thereby implementing any of the disclosed techniques. For example, software for implementing any of the disclosed embodiments may be stored on one or more volatile, non-transitory computer-readable media as computer-executable instructions that, when executed by one or more processors, cause the one or more processors to implement any of the disclosed techniques or a subset of the techniques.

[0143] Although the principles of the disclosed technology have been described and illustrated with reference to illustrated examples, it will be recognized that the illustrated examples may be modified in arrangement and detail without departing from such principles. For example, elements of an example implemented in software may be implemented in hardware, and vice versa. Also, techniques from any example may be combined with techniques described in any one or more of the other examples. It will be understood that procedures and functions as described with reference to the illustrated examples may be implemented in a single hardware or software module, or may be provided as separate modules. The particular configuration above is provided for convenient illustration, and other configurations may be used.

[0144] Additional Examples of the Disclosed Technology In view of the above-described implementations of the disclosed subject matter, the present application discloses the following additional embodiments: It should be noted that one feature of a single embodiment, or a combination of two or more features of that embodiment, optionally in combination with one or more features of one or more additional embodiments, is also a further embodiment that falls within the disclosure of the present application.

[0145] Example 1. A method of operating a charged particle microscope (CPM) system having a beam deflector positioned at a deflector plane, the CPM system configured to direct a charged particle beam at a sample to generate a diffraction beam pattern at a diffraction plane, the method including adjusting one or more optical elements of the CPM system so that the deflector plane is conjugate with the diffraction plane, and recording the diffraction beam pattern using a detector positioned at the diffraction plane.

[0146] Example 2. The method of example 1, wherein adjusting the one or more optical elements includes adjusting the position of the diffraction plane to axially align the diffraction plane with the detector.

[0147] Example 3. The method of example 2, wherein the CPM system comprises a first optical assembly positioned upstream of the deflector plane and a second optical assembly positioned downstream of the deflector plane, and adjusting the position of the diffraction plane comprises adjusting one or more optical elements of the second optical assembly.

[0148] Example 4. The method of example 3, wherein the method further includes adjusting one or more optical elements of the first optical assembly to axially align a crossover plane of the charged particle beam with the detector.

[0149] Example 5. The method of example 3 or 4, wherein adjusting one or more optical elements of the first optical assembly is performed subsequent to adjusting one or more optical elements of the second optical assembly.

[0150] Example 6. The method of any one of Examples 3-5, wherein adjusting one or more optical elements of the first optical assembly is performed before adjusting one or more optical elements of the second optical assembly.

[0151] Example 7. The method of any one of Examples 3-6, wherein the CPM system is configured to generate an adjusted beam pattern at the detector, and adjusting one or more optical elements of the second optical assembly includes adjusting the adjusted beam pattern so that it becomes increasingly unfocused at the detector.

[0152] Example 8. The method of any one of Examples 3-7, wherein adjusting one or more optical elements of the first optical assembly includes adjusting a first focal length associated with the first optical assembly.

[0153] Example 9. The method of example 8, wherein adjusting one or more optical elements of the second optical assembly includes adjusting a second focal length associated with the second optical assembly.

[0154] Example 10. The method of any one of Examples 7-9, wherein one or both of adjusting the first focal length and adjusting the second focal length comprises adjusting an excitation voltage applied to the electro-optic lens.

[0155] Example 11. The method of any one of Examples 3-10, wherein the CPM system comprises a source optical assembly configured to accelerate the charged particle beam toward the sample, and the first optical assembly comprises at least a portion of the source optical assembly.

[0156] Example 12. The method of any one of Examples 3-11, wherein the second optical assembly comprises at least a portion of a condenser optical assembly of a CPM system.

[0157] Example 13. The method of any one of Examples 3-12, wherein the second optical assembly comprises at least a portion of an objective optical assembly.

[0158] Example 14. The method of any one of Examples 3-13, wherein adjusting one or more optical elements of the second optical assembly includes adjusting one or more optical elements positioned downstream of the sample.

[0159] Example 15. The method of any one of Examples 3-14, wherein the second optical assembly comprises one or more objective lens elements.

[0160] Example 16. The method of any one of Examples 3-15, wherein adjusting the position of the diffraction plane comprises axially shifting the position of the diffraction plane.

[0161] Example 17. The method of any one of Examples 1-16, wherein the diffraction beam pattern comprises a diffractogram.

[0162] Example 18. The method of any one of Examples 1-17, further comprising directing the charged particle beam at the sample in the form of beam pulses of variable beam pulse duration, and operating a beam deflector to vary the beam pulse duration to perform a time-resolved diffraction study of the sample.

[0163] Example 19. The method of any one of Examples 1-18, wherein the CPM system is configured such that the charged particle beam is at least substantially undeflected by the beam deflector when the beam deflector is in an unblanked state, the beam deflector is configured to selectively deflect the charged particle beam away from the sample when the beam deflector is in a fully blanked state, and the beam deflector is configured to direct the charged particle beam along a trajectory that results in a partially blanked beam pattern in the diffraction plane when the beam deflector is in one of a plurality of partially blanked states defined between the unblanked state and the fully blanked state, and the method includes operating the CPM system such that the partially blanked beam pattern is substantially stationary in the deflector plane when the beam deflector transitions from the unblanked state to the fully blanked state.

[0164] Example 20. The method of any one of Examples 1 to 19, wherein adjusting one or more optical elements of the CPM system is performed at least in part while the sample is positioned in the beam path of the charged particle beam.

[0165] Example 21. The method of any one of Examples 1 to 20, wherein adjusting one or more optical elements of the CPM system is performed at least in part while the sample is removed from the beam path of the charged particle beam.

[0166] Example 22. A method of operating a charged particle microscope (CPM) system, the method comprising: directing a charged particle beam toward a sample, the sample adjusting the charged particle beam to create a beam pattern downstream of the sample; transitioning a beam blanker of the CPM system positioned at a deflector plane between an unblanked state in which the charged particle beam reaches the sample and a blanked state in which the charged particle beam is directed away from the sample; and recording the beam pattern using a detector positioned at a detector plane conjugate to the deflector plane, wherein the beam pattern comprises one or more beam pattern features that are focused in the detector plane, and the one or more beam pattern features are substantially stationary in the detector plane as the beam blanker transitions between the unblanked state and the blanked state.

[0167] Example 23. The method of example 22, wherein the beam blanker comprises an electrostatic beam blanker.

[0168] Example 24. The method of example 22 or 23, wherein transitioning the beam blanker between the unblanked state and the blanked state is performed over a period of time that is less than 10 nanoseconds (ns).

[0169] Example 25. The method of any one of Examples 22 to 24, further comprising configuring the CPM system in a conjugate blanking configuration in which the deflector plane is conjugate to the detector plane and the crossover of the charged particle beam is positioned at the deflector plane, and configuring the CPM system comprises bringing the CPM system to an intermediate configuration in which the detector plane is conjugate to the deflector plane, and following bringing the CPM system to the intermediate configuration, bringing the CPM system to the conjugate blanking configuration.

[0170] Example 26. The method of Example 25, wherein configuring the CPM system in the conjugate blanking configuration is performed at least in part before directing the charged particle beam at the sample.

[0171] Example 27. The method of example 25 or 26, wherein configuring the CPM system in the conjugate blanking configuration is performed at least in part subsequent to directing the charged particle beam at the sample.

[0172] Example 28. The method of any one of Examples 25-27, wherein bringing the CPM system to the intermediate configuration includes shifting a conjugate deflector plane into axial alignment with a detector plane.

[0173] Example 29. The method of any one of Examples 25-28, wherein bringing the CPM system to the intermediate configuration includes adjusting the focal length of one or more optical elements downstream of the deflector plane.

[0174] Example 30. A method according to any one of Examples 25 to 29, wherein bringing the CPM system to the intermediate configuration includes adjusting a beam blanker between an unblanked state and a blanked state to move a test beam pattern feature of the one or more beam pattern features within the detector plane, and adjusting one or more optical elements downstream of the deflector plane to fix the test beam pattern feature in a substantially stationary position within the deflector plane while adjusting the beam blanker between the unblanked state and the blanked state.

[0175] Example 31. The method of example 30, wherein adjusting the beam blanker and adjusting one or more optical elements downstream of the deflector plane are performed at least partially simultaneously.

[0176] Example 32. The method of any one of Examples 25 to 31, wherein bringing the CPM system into the conjugate blanking configuration includes focusing the beam pattern at the detector plane while the CPM system is in an intermediate configuration.

[0177] Example 33. The method of Example 32, wherein focusing the beam pattern includes adjusting one or more optical elements upstream of the deflector plane to bring the crossover plane of the charged particle beam to the detector plane.

[0178] Example 34. The method of example 32 or 33, wherein focusing the beam pattern at the detector plane includes adjusting the focal length of one or more optical elements upstream of the deflector plane.

[0179] Example 35. The method of any one of Examples 18-34, further comprising directing the charged particle beam at the sample in the form of beam pulses of variable beam pulse duration, and operating a beam blanker to vary the beam pulse duration to perform a time-resolved diffraction study of the sample.

[0180] Example 36. A charged particle microscope (CPM) system comprising: a charged particle source configured to emit a charged particle beam along an optical axis toward a sample; a first optical assembly positioned downstream of the charged particle source and configured to change the axial position of a focal plane of the charged particle beam upstream of the sample; a beam deflector positioned at a deflector plane downstream of the first optical assembly and configured to selectively redirect the charged particle beam away from the sample; a second optical assembly positioned downstream of the deflector plane; and a detector positioned at a detector plane downstream of the second optical assembly, wherein the CPM system is configured such that the charged particle beam exhibits a beam crossover at the deflector plane and such that the deflector plane is imaged onto the detector.

[0181] Example 37. A CPM system as described in Example 36, wherein the first optical assembly comprises a gun lens configured to adjust the axial position of the beam crossover, and the CPM system is configured such that the gun lens remains at a fixed excitation when the CPM system is in operational use.

[0182] Example 38. A CPM system as described in Example 36 or 37, wherein the second optical assembly comprises one or both of a condenser optical assembly and an objective optical assembly.

[0183] Example 39. The CPM system of any one of Examples 36-38, wherein one or more components of the second optical assembly are positioned downstream of the sample.

[0184] Example 40. A CPM system described in any one of Examples 36 to 39, further comprising a blanking aperture, wherein the beam deflector is configured to selectively direct the charged particle beam so that it is blocked by the blanking aperture.

[0185] Example 41. The CPM system of Example 40, wherein the second optical assembly comprises a blanking aperture.

[0186] Example 42. A CPM system described in any one of Examples 36 to 41, wherein the beam deflector is configured to direct the charged particle beam toward the sample in the form of beam pulses of variable beam pulse duration to perform time-resolved diffraction studies of the sample.

[0187] Features described herein with respect to any embodiment may be combined with other features described in any one or more of the other embodiments, unless stated otherwise. For example, any one or more steps and / or features of one method may be combined with any one or more steps and / or features of another method.

[0188] In view of the many possible ways in which the principles of this disclosure may be applied, it should be recognized that the illustrated configurations depict examples of the disclosed technology and should not be construed as limiting the scope of the disclosure or the claims. Rather, the scope of claimed subject matter is defined by the following claims and their equivalents.

Claims

1. 1. A method of operating a charged particle microscope (CPM) system comprising a beam deflector positioned at a deflector plane, the CPM system configured to direct a charged particle beam at a sample to generate a diffraction beam pattern at a diffraction plane, the method comprising: adjusting one or more optical elements of the CPM system so that the deflector plane is conjugate with the diffraction plane; and recording the diffracted beam pattern with a detector positioned at the diffraction plane.

2. The method of claim 1 , wherein adjusting the one or more optical elements comprises adjusting a position of the diffraction plane to axially align the diffraction plane with the detector.

3. 3. The method of claim 2, wherein the CPM system comprises a first optical assembly positioned upstream of the deflector plane and a second optical assembly positioned downstream of the deflector plane, and wherein adjusting the position of the diffraction plane comprises adjusting one or more optical elements of the second optical assembly, and the method further comprises adjusting one or more optical elements of the first optical assembly to axially align a crossover plane of the charged particle beam with the detector.

4. The method of claim 3 , wherein adjusting the one or more optical elements of the first optical assembly is performed subsequent to adjusting the one or more optical elements of the second optical assembly.

5. 4. The method of claim 3, wherein adjusting the one or more optical elements of the first optical assembly comprises adjusting a first focal length associated with the first optical assembly, and adjusting the one or more optical elements of the second optical assembly comprises adjusting a second focal length associated with the second optical assembly.

6. 4. The method of claim 3, wherein the CPM system comprises a source optical assembly configured to accelerate the charged particle beam toward the specimen, and the first optical assembly comprises at least a portion of the source optical assembly.

7. The method of claim 3 , wherein the second optical assembly comprises at least a portion of a condenser optical assembly of the CPM system.

8. The method of claim 3 , wherein the second optical assembly comprises at least a portion of an objective optical assembly.

9. The method of claim 3 , wherein adjusting the position of the diffraction plane comprises axially shifting the position of the diffraction plane.

10. 2. The method of claim 1, wherein the CPM system is configured such that the charged particle beam is at least substantially undeflected by the beam deflector when the beam deflector is in an unblanked state, the beam deflector is configured to selectively deflect the charged particle beam away from the sample when the beam deflector is in a fully blanked state, and the beam deflector is configured to direct the charged particle beam along a trajectory that results in a partially blanked beam pattern in the diffraction plane when the beam deflector is in one of a plurality of partially blanked states defined between the unblanked state and the fully blanked state, the method comprising operating the CPM system such that the partially blanked beam pattern is substantially stationary in the deflector plane when the beam deflector transitions from the unblanked state to the fully blanked state.

11. 1. A method of operating a charged particle microscope (CPM) system, the method comprising: directing a charged particle beam at a sample, the sample adjusting the charged particle beam to create a beam pattern downstream of the sample; transitioning a beam blanker of the CPM system positioned at a deflector plane between an unblanked state in which the charged particle beam reaches the sample and a blanked state in which the charged particle beam is directed away from the sample; recording the beam pattern using a detector positioned at a detector plane that is conjugate to the deflector plane; The method, wherein the beam pattern includes one or more beam pattern features that are focused in the detector plane, and the one or more beam pattern features are substantially stationary in the detector plane when the beam blanker transitions between the unblanked state and the blanked state.

12. 12. The method of claim 11, wherein transitioning the beam blanker between the unblanked state and the blanked state is performed over a period of time that is less than 10 nanoseconds (ns).

13. further comprising configuring the CPM system in a conjugate blanking configuration, wherein the deflector plane is conjugate to the detector plane and a crossover of the charged particle beam is positioned at the deflector plane, and configuring the CPM system includes: bringing the CPM system to an intermediate configuration in which the detector plane is conjugate with the deflector plane; The method of claim 11 , further comprising: subsequently bringing the CPM system to the intermediate configuration, bringing the CPM system to the conjugate blanking configuration.

14. The method of claim 13 , wherein bringing the CPM system to the intermediate configuration comprises adjusting a focal length of one or more optical elements downstream of the deflector plane.

15. bringing the CPM system to the intermediate configuration; adjusting the beam blanker between the unblanked state and the blanked state to move a test beam pattern feature of the one or more beam pattern features within the detector plane; 14. The method of claim 13, further comprising: adjusting one or more optical elements downstream of the deflector plane to fix the test beam pattern feature in a substantially stationary location in the deflector plane while adjusting the beam blanker between the unblanked state and the blanked state.

16. The method of claim 13 , wherein bringing the CPM system into the conjugate blanking configuration comprises focusing the beam pattern at the detector plane while the CPM system is in the intermediate configuration.

17. The method of claim 16 , wherein focusing the beam pattern at the detector plane comprises adjusting a focal length of one or more optical elements upstream of the deflector plane.

18. 1. A charged particle microscope (CPM) system comprising: a charged particle source configured to emit a charged particle beam along an optical axis toward the sample; a first optical assembly positioned downstream of the charged particle source and configured to vary an axial position of a focal plane of the charged particle beam upstream of the specimen; a beam deflector positioned in a deflector plane downstream of the first optical assembly and configured to selectively redirect the charged particle beam away from the sample; a second optical assembly positioned downstream of the deflector plane and configured to vary an axial position of a focal plane of the charged particle beam downstream of the specimen; a detector positioned at a detector plane downstream of the second optical assembly; The CPM system is configured such that the charged particle beam exhibits a beam crossover at the deflector plane, and such that the deflector plane is imaged onto the detector.

19. 20. The CPM system of claim 18, wherein the first optical assembly comprises a gun lens configured to adjust an axial position of the beam crossover, and the CPM system is configured such that the gun lens remains at a fixed excitation when the CPM system is in operational use.

20. 20. The CPM system of claim 18, wherein the second optical assembly comprises one or both of a condenser optical assembly and an objective optical assembly.

21. 20. The CPM system of claim 18, wherein one or more components of the second optical assembly are positioned downstream of the sample.

22. 20. The CPM system of claim 18, further comprising a blanking aperture, the beam deflector configured to selectively direct the charged particle beam to be blocked by the blanking aperture.

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