Data processing device, transmission electron microscope device, and program

Abstract

To provide a technique that, when measuring the magnetic structure in a sample using a transmission electron microscope, enables at least one of shortening a data processing time and improving the measurement accuracy of the fine magnetic structure of the sample.SOLUTION: A data processing device 20 processes detection data of electrons transmitted through a sample 1 by irradiating the sample 1 with a convergent electron beam. The detection data includes detection intensities indicating the total amount of electrons transmitted through each detection region located on opposite sides of the central axis of the convergent electron beam. The data processing device 20 includes a difference acquisition unit 21 and a data measurement unit 22. The difference acquisition unit 21 calculates the difference between the detection intensities of the detection regions on the opposite sides. The data measurement unit 22 measures magnetization information data indicating magnetization information inside the sample 1 on the basis of the difference.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for irradiating a sample with a convergent electron beam and measuring magnetization information inside the sample based on detection data of electrons that have transmitted through the sample. [Background technology]

[0002] Conventionally, electron holographic tomography of three-dimensional magnetization structures and three-dimensional Lorentz microscopy (Lorentz TEM) (e.g., Patent Document 1 below) are microscopic techniques for non-invasively visualizing magnetic structures and behaviors in materials. These techniques play an important role in fields such as materials science and condensed matter physics. From an application perspective, these techniques also play an important role in the design and optimization of magnetic materials, such as the development of magnetic memory devices, magnetic data storage, and magnetic sensors.

[0003] Electron holography and Lorentz microscopy (Lorentz TEM) are methods for investigating the magnetic field distribution within a magnetic sample based on the deflection of an electron beam due to the Lorentz force when it passes through the sample. Electron holographic tomography requires days to weeks to evaluate the three-dimensional magnetic structure of a sample due to the cumbersome data recording process. Compared to electron holography, Lorentz microscopy allows for the simultaneous tracking of the dynamic behavior of the magnetic structure within the sample under external fields (such as temperature and magnetic field) without damaging the sample. Applications of Lorentz microscopy are particularly important for understanding magnetic structures in materials science, physics, and spintronics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-233076 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Lorentz microscopy tomography can only provide qualitative information about the magnetic field distribution within a material, and data processing is time-consuming, in part because complementary techniques, such as analytical tools that utilize the transport-of-intensity equation, are required to derive semi-quantitative information about the vector field.

[0006] Furthermore, when observing three-dimensional magnetization structures using Lorentz microscope tomography, the range of sample tilt angles is limited to ±50 degrees, which leads to a "nicked-out problem" that may impair the spatial resolution or accuracy of the three-dimensional field distribution within the material.

[0007] Therefore, an object of the present invention is to provide a technology that enables at least one of shortening data processing time and improving measurement accuracy of the fine three-dimensional magnetization structure of a sample when measuring the three-dimensional magnetization structure within the sample using a transmission electron microscope. [Means for solving the problem]

[0008] In order to achieve the above object, a data processing device according to one aspect of the present invention is a data processing device that processes detection data of electrons that have passed through a sample by irradiating the sample with a convergent electron beam, the data processing device comprising: the detection data includes, for each of detection regions located on opposite sides of the central axis of the convergent electron beam, a detection intensity indicating a total amount of electrons transmitted to the detection region; a difference acquisition unit that calculates a difference between the detection intensities of the detection regions opposite to each other; and a data measurement unit that measures magnetization information data indicating magnetization information inside the sample based on the difference.

[0009] A transmission electron microscope apparatus according to one aspect of the present invention comprises: the data processing device described above; an electron beam irradiation device that irradiates the sample with the convergent electron beam; a control device that controls scanning of a scanning region on the sample with the convergent electron beam; and a detection device that detects electrons that have passed through the sample as a result of the irradiation and measures the detection data.

[0010] A program according to one aspect of the present invention is a program for processing detection data of electrons transmitted through a sample by irradiating the sample with a convergent electron beam, the program comprising: the detection data includes, for each of detection regions located on opposite sides of the central axis of the convergent electron beam, a detection intensity indicating a total amount of electrons transmitted to the detection region; A process of calculating a difference between the detection intensities of the detection regions opposite to each other; and measuring magnetization information data indicating magnetization information inside the sample based on the difference. [Effects of the Invention]

[0011] According to the present invention, when measuring the three-dimensional magnetization structure in a sample using a transmission electron microscope, it is possible to at least either shorten the data processing time or improve the measurement accuracy of the fine magnetization structure of the sample. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a schematic configuration of a transmission electron microscope apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a view taken along the line II-II in FIG. 1, showing a plurality of detection regions in a detector. [Figure 3] 1 is a block diagram showing a configuration of a data processing device according to an embodiment of the present invention; [Figure 4] FIG. 1 is an explanatory diagram of a magnetic field within a sample and deflection of an electron beam. [Figure 5A] An example of differential phase contrast (DPC) data is shown. [Figure 5B] An example of integrated phase contrast (iDPC) data is shown. [Figures 6A-6D] 1 shows image data actually obtained by a transmission electron microscope apparatus according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings. In addition, common parts in the drawings are given the same reference numerals, and duplicated explanations will be omitted.

[0014] (Configuration of transmission electron microscope equipment) FIG. 1 shows a schematic configuration of a transmission electron microscope apparatus 10 according to an embodiment of the present invention. The transmission electron microscope apparatus 10 according to this embodiment is an apparatus for irradiating a sample 1, which is an object to be measured, with an electron beam, obtaining detection data of the electrons that have transmitted through the sample 1, and acquiring magnetization information within the sample 1 based on the detection data. More specifically, the transmission electron microscope apparatus 10 irradiates each scanning position within a predetermined scanning region on the sample 1 with an electron beam (hereinafter simply referred to as a convergent electron beam) that converges on the sample 1 (e.g., the surface 1a of the sample 1), and detects the electrons that have transmitted through the sample 1 in each of detection regions D1 to D4, which will be described later, to measure the detection data. Furthermore, the transmission electron microscope apparatus 10 measures magnetization information data that represents magnetization information within the sample 1 based on this detection data.

[0015] The transmission electron microscope apparatus 10 includes an electron beam irradiation device 11 , a control device 12 , a detection device 13 , and a data processing device 20 .

[0016] The electron beam irradiation device 11 irradiates a convergent electron beam onto the sample 1. The electron beam irradiation device 11 includes, for example, an electron source 11a that generates an electron beam and a lens group 11b that converges the electron beam from the electron source 11a at a position (e.g., the surface 1a) of the sample 1. The electron source 11a may be an electron gun. The lens group 11b includes, for example, a focusing lens 11b1 as an electron lens and an objective lens 11b2.

[0017] In the following, the x direction, y direction, and z direction refer to the directions indicated by x, y, and z in FIGS. 1 and 2, respectively. Furthermore, in the following, the xyz coordinate system refers to a coordinate system fixed to a stationary system (for example, a detector 13a described below), and the directions of its x, y, and z axes are the x direction, y direction, and z direction, respectively. The x direction and y direction are directions perpendicular to the central axis C of the convergent electron beam incident on the sample 1 and intersect each other (for example, perpendicular), and the z direction is a direction parallel to the central axis C. Furthermore, in the xyz coordinate system, a position represented by the x coordinate and the y coordinate may be represented by (x, y), and a position represented by the x coordinate, the y coordinate, and the z coordinate may be represented by (x, y, z).

[0018] The control device 12 controls the scanning of a two-dimensional scanning region on the sample 1 with a convergent electron beam. The scanning region is a region along a plane perpendicular to the z direction. In this embodiment, the control device 12 controls the driving device 14 to move the sample 1 in the x and y directions so that the scanning region on the sample 1 is scanned with the convergent electron beam. The driving device 14 is configured to move the sample 1 in each of the x and y directions while holding the sample 1. Through the above control, the convergent electron beam is irradiated onto each scanning position (x, y) within the scanning region on the sample 1.

[0019] In addition to controlling the driving device 14, the control device 12 may also control each part of the transmission electron microscope apparatus 10. For example, the control device 12 may control the start and end of electron beam generation by the electron source 11a by controlling the voltage applied to the electron source 11a. Furthermore, the control device 12 may control the detection time of the intensity detection unit 13b of the detection device 13, as will be described later.

[0020] The detection device 13 detects electrons transmitted through the sample 1 as a result of irradiating the sample 1 with a convergent electron beam, and measures detection data indicating the detection results. The detection device 13 has a detector 13a and an intensity detection unit 13b.

[0021] 2 is a view taken along the arrows II-II in FIG. 1. The detector 13a has first to fourth detection regions D1 to D4 arranged on the back surface 1b side of the sample 1. The first and third detection regions D1, D3 are located on opposite sides of each other in the x direction with respect to the central axis C. The second and third detection regions D2, D4 are located on opposite sides of each other in the y direction with respect to the central axis C. The detector 13a may be a segmented detector 13a in which the multiple detection regions D1 to D4 are separated from each other. The transmission electron microscope apparatus 10 may be set so that the center of the detector 13a is located on the central axis C of the convergent electron beam.

[0022] The multiple detection areas D1 to D4 may be areas included in the same plane. Furthermore, each pair of detection areas D1, D3 and D2, D4 on opposite sides of the central axis C may be symmetrical with respect to the central axis C. In the example of FIG. 2, the multiple detection areas D1 to D4 are sectors of the same size and shape. In this case, the centers of the sectors are located on the central axis C.

[0023] The intensity detection unit 13b detects, for each of the detection regions D1, D2, D3, and D4, an intensity indicating the total amount of transmitted electrons (electrons that have transmitted through the sample 1) that are incident on the detection region. In this embodiment, for each scanning position (x, y) within the scanning region on the sample 1, the intensity detection unit 13b detects the intensity of electrons detected in each of the detection regions D1, D2, D3, and D4 as a result of irradiating the scanning position with a convergent electron beam.

[0024] Such detection may be controlled by the control device 12. For example, the control device 12 may perform the following control for each scanning position (x, y): For each scanning position (x, y), the control device 12 moves the sample 1 in the x direction or y direction via the driving device 14 so that the focused electron beam is irradiated onto the scanning position, supplies power to the electron source 11a to irradiate the focused electron beam onto the scanning position, and causes the intensity detection unit 13b to detect the intensities of electrons detected in each of the detection regions D1, D2, D3, and D4 over a certain detection time.

[0025] The electron intensity in each detection region D1 to D4 is detected while scanning each scanning position (x, y) within the scanning region of the sample 1 with a convergent electron beam. That is, the intensity of transmitted electrons incident on each detection region D1 to D4 is detected by the incidence of the convergent electron beam on the scanning position (x, y). Hereinafter, the electron intensity detected in each detection region D1, D2, D3, D4 as a result of irradiating each scanning position with the convergent electron beam is also simply referred to as the detected intensity.

[0026] The intensity detector 13b measures the above-mentioned detection data and outputs the detection data to the data processor 20. This detection data is data that correlates each scanning position (x, y) with the detection intensity in each detection region D1, D2, D3, and D4. Such detection data will be simply referred to as detection data below.

[0027] (Configuration of data processing device) 3 is a block diagram showing the configuration of the data processing device 20. The data processing device 20 includes a difference acquisition unit 21, a data measurement unit 22, and a reconstruction unit .

[0028] <Difference acquisition section and data measurement section> The difference acquiring unit 21 calculates the difference between the detection intensities of the detection regions on the opposite sides based on the detection data. In this embodiment, the difference acquiring unit 21 calculates the difference ΔI between the detection intensities of the first and third detection regions D1 and D3 for each scanning position (x, y) (i.e., for the irradiation of the convergent electron beam at each scanning position) as an x-direction difference I x Further, the difference acquiring unit 21 calculates the difference ΔI between the detection intensities in the second and fourth detection areas D2 and D4 for each scanning position (x, y) based on the detection data as the y-direction difference I y That is, when the detection intensities in the detection areas D1 to D4 are I1 to I4, respectively, I x = I1 - I3, and I y =I2-I4. In the following, I for each scanning position (x, y) x and I y I x (x,y) and I yIt may be written as (x,y).

[0029] The data measurement unit 22 measures magnetization information data indicating magnetization information inside the sample 1 based on the difference obtained by the difference acquisition unit 21. In this embodiment, for each scanning position (x, y), the data measurement unit 22 measures magnetization information data F(x, y) indicating magnetization at the position (x, y) in the sample 1 based on the difference corresponding to the scanning position (x, y). Note that F(x, y) may be, for example, magnetic flux density B(x, y) or vector potential A(x, y) of a magnetic field.

[0030] More specifically, the data measurement unit 22 measures the x-direction difference I obtained by the difference acquisition unit 21 for each scanning position (x, y). x The y-direction component of the magnetization information data F(x, y) is calculated based on the y The x-direction component of the magnetization information data F(x, y) is calculated based on the above equation.

[0031] The electron beam undergoes a phase shift due to the influence of the magnetic field of the sample 1 when passing through the sample 1. The phase shift amount φ at the position (x, y) is OUT (x, y) is expressed by the following equation (1).

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[0032] Generally, it is said that the phase shift of an electron beam due to a magnetic field is two or more orders of magnitude larger than the phase shift of an electron beam due to an electric field. Therefore, in this embodiment, the first term relating to V(x, y, z) on the right side of equation (1) is expressed as A zWe use the approximation that the first term in V(x,y,z) does not exist, assuming that it is sufficiently smaller than the second term in (x,y,z).

[0033] φ in the x direction OUT Function φ as (x,y) OUT,x The Fourier transform of (x,y) is Δφ x and φ in the y direction OUT Function φ as (x,y) OUT,y (x,y) to Δφ y In this case, the x-direction difference I obtained by the difference acquisition unit 21 is x and the y-direction difference I y are expressed by the following equations (2) and (3), respectively.

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[0034] Furthermore, when an electron beam with wavelength λ passes through sample 1, which is a magnetic material (e.g., a ferromagnetic material) and has a thickness t, the electron beam is deflected by the magnetic field generated by sample 1. As a result, the center of the range of incidence of the electron beam on detector 13a is shifted from its position on central axis C. For example, as shown in FIG. 4, if magnetic flux density B pointing in the y direction is present at position (x, y) in sample 1 where the convergent electron beam passes, the electron beam passing through sample 1 is subjected to a Lorentz force in the x direction due to magnetic flux density B, causing the center of the range of incidence of the electron beam on detector 13a to be shifted in the x direction (negative x direction) from its position on central axis C. The angle θ at which the electron beam is deflected in this way is expressed by the following equation (4):

[0035]

number

[0036] For example, the angle (deflection angle) at which electrons are deflected in the x direction by passing through the sample 1 at position (x, y) in the xz plane is the y-direction component B of the magnetic flux density B(x, y) at position (x, y) in the sample 1. y is proportional to the thickness t of the sample 1 in the (x, y) and z directions. In this regard, this deflection angle is the x-direction difference I x It can be said that it is also proportional to (x, y).

[0037] So, B y The known z-direction dimension of the area where (x, y) exists (area of ​​sample 1) is set to t0, and the x-direction difference I x B for (x,y) y The ratio of (x, y)t0 is calculated in advance. For example, in the region where the sample 1 is placed, the y-direction component of the magnetic flux density B yThe z-direction dimension of the region corresponds to the thickness of the sample 1 and is assumed to be a known value t0. Using the transmission electron microscope device 10, an electron beam is incident on the region, and the difference acquisition unit 21 calculates I as described above. x (x,y) is calculated. Then, x B for (x,y) y The ratio of (x, y)t0 is calculated. The ratio calculated in this manner may be stored in advance in the data measurement unit 22. The data measurement unit 22 may also store in advance the thickness t in the z direction of the sample 1 to be measured.

[0038] Then, the measurement of the sample 1 to be measured may be performed. That is, using the transmission electron microscope device 10, an electron beam is incident on the sample 1 in the above-mentioned region, and the difference acquisition unit 21 acquires the I x Next, the data measurement unit 22 calculates the I x Based on (x, y), the stored ratio, the z-direction dimension t0 of the region, and the z-direction thickness t of the sample 1, the y-direction component B of the magnetic flux density in the sample 1 is calculated. y (x,y) or B y (x,y)t is calculated. Here, B y To find (x,y), use B y (x,y) can be assumed to be uniform in the z direction. B y When (x, y)t is to be calculated, the thickness t of the sample 1 does not need to be used.

[0039] y direction difference I y Similarly, for (x, y), B y The known z-direction dimension of the area where (x, y) exists (area of ​​sample 1) is set to t0, and the y-direction difference I y B for (x,y) x The ratio of (x, y)t0 is calculated in advance. Then, when measuring the sample 1 to be measured, the data measurement unit 22 calculates the ratio of I calculated by the difference acquisition unit 21. y Based on (x, y), the stored ratio, the z-direction dimension t0 of the region, and the z-direction thickness t of the sample 1, the x-direction component B of the magnetic flux density in the sample 1 is calculated. x (x,y) or Bx (x,y)t is calculated. Here, B x To find (x, y), use B x (x,y) can be assumed to be uniform in the z direction. B x When (x, y)t is to be calculated, the thickness t of the sample 1 does not need to be used.

[0040] The conditions for determining the ratio are the same as those for measuring the sample 1. The conditions include the intensity of the electrons generated by the electron source 11a.

[0041] <Reconstruction part> The reconstruction unit 23 reconstructs three-dimensional magnetization information data F(x,y,z) at each three-dimensional position (x,y,z) in the sample 1 based on the above-mentioned two-dimensional magnetization information data F(x,y) obtained for each of the multiple angles of incidence of the convergent electron beam, as follows. Here, the two-dimensional magnetization information data F(x,y) may be, for example, magnetic flux density B(x,y) or vector potential A(x,y) multiplied by the z-direction thickness t of the sample 1. Note that A(x,y) is calculated from the magnetic flux density B(x,y) by the data measurement unit 22, assuming that no electrostatic potential V(x,y,z) exists in the sample 1. Also, the magnetic flux density B(x,y) is calculated by multiplying the x-direction component B(x,y) calculated by the data measurement unit 22 as described above. x (x,y) and y-direction component B y It may consist of (x,y).

[0042] To obtain three-dimensional magnetization information data F(x, y, z), the transmission electron microscope apparatus 10 changes the incident angle of the convergent electron beam and measures the above-mentioned detection data each time the angle is changed. To this end, the drive device 14 is controlled by the control device 12 to tilt the sample 1 with respect to the xy plane. This makes it possible to change the incident angle (hereinafter simply referred to as the incident angle) of the convergent electron beam with respect to the sample 1 (e.g., the surface 1a of the sample 1). For example, the drive device 14 is controlled by the control device 12 to tilt the sample 1 around an axis passing through the sample 1 and parallel to the x-axis.

[0043] The control device 12 changes the angle of incidence to multiple angles via the drive device 14. The control device 12 also controls the detection device 13 (intensity detection unit 13b) as described above so that detection data corresponding to each angle of incidence can be obtained. That is, the control device 12 sets the angle of incidence to one value, controls the electron beam irradiation device 11 (electron source 11a and drive device 14) to irradiate each scanning position (x, y) within the scanning area with a convergent electron beam under this condition, and controls the detection device 13 (intensity detection unit 13b) to measure detection data that correlates each scanning position (x, y) with the detection intensity at each detection area D1, D2, D3, and D4. Next, the control device 12 sets the angle of incidence to another value and performs similar control to cause the detection device 13 to measure detection data. The control device 12 repeats this control process to cause the detection device 13 to measure detection data for each of the multiple angles of incidence.

[0044] The data processing device 20 measures the magnetization information data F(x, y) as described above based on the detection data measured by the detection device 13 for each incident angle. That is, for each incident angle, the data processing device 20 measures the magnetization information data F(x, y) corresponding to that incident angle based on the detection data corresponding to that incident angle. The magnetization information data F(x, y) is two-dimensional data when a convergent electron beam passes through the sample 1 at a position (x, y) on the sample 1. That is, the magnetization information data F(x, y) is two-dimensional data having values ​​(for example, the above-mentioned x component and y component) at each position coordinate (x, y).

[0045] The reconstruction unit 23 reconstructs three-dimensional magnetization information data F(x, y, z) relating to the magnetization at each three-dimensional position (x, y, z) in the sample 1 based on the two-dimensional magnetization information data (x, y) corresponding to each incident angle. At this time, the reconstruction unit 23 may store in advance the coordinate range in which the sample 1 exists (such as the z-direction thickness of the sample 1 or the scanning range), and may reconstruct the three-dimensional magnetization information data F(x, y, z) based on this coordinate range as well. This reconstruction may be performed by, for example, simultaneous iterative reconstruction (SIRT) method, filtered back projection (FBP) method, iterative image reconstruction (IR) method, or the like.

[0046] For example, the reconstruction unit 23 performs reconstruction processing assuming that the x-direction component of the two-dimensional magnetization information data F(x, y) is obtained by integrating the magnetization information value (for example, the x-direction component of the magnetic flux density) at each z-coordinate (unit area) in the sample 1 for the position (x, y) over the z-direction range of the sample 1. In this case, for example, the x-coordinate is expressed as x i A plane parallel to the yz plane (x=x i ) for the magnetization information data F(x i , y) is extracted from a large number of magnetization information data F(x, y) corresponding to a large number of incident angles. i , y) based on the above one plane (x=x i ) on each coordinate (x i , y, z) i ,y,z) is reconstructed. This reconstruction is called x i This is repeated by changing the value of . As a result, the reconstruction unit 23 reconstructs the magnetization information value of the three-dimensional magnetization information data F(x, y, z) related to the magnetization at each three-dimensional position (x, y, z) in the sample 1. In this way, the reconstruction unit 23 reconstructs the x-direction component (e.g., magnetic flux density) of the magnetization information data F(x, y, z) at each three-dimensional position (x, y, z).

[0047] Similarly, the reconstruction unit 23 reconstructs the y-direction component (magnetization information value) of three-dimensional magnetization information data F(x, y, z) relating to the magnetization at each three-dimensional position (x, y, z) in the sample 1.

[0048] The data processing device 20 stores the measured data in a predetermined storage device and outputs the data. The output destination of the data may be, for example, a display device 31 as shown in Fig. 3. In this case, the display device 31 may display the data as follows.

[0049] As described above, the display device 31 displays, as a three-dimensional image, the magnetic flux density B(x, y, z) or the vector potential A(x, y, z), which is the three-dimensional F(x, y, z) measured by the reconstruction unit 23. In this case, the display device 31 may display the xyz coordinate space three-dimensionally, and may also display, with arrows, vectors representing B(x, y, z) or A(x, y, z) at each position (x, y, z) in the xyz coordinate space.

[0050] (Integrated phase contrast) In this embodiment, the scalar potential (phase) of the electromagnetic field is the scalar potential of the magnetic field (magnetic flux density B) in the sample 1, and I in the following equation (5) is iDPC The integrated data is used, such as in integrated differential-phase contrast (iDPC), which utilizes the

[0051]

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[0052] In Figure 5A, the horizontal axis indicates the point (x, y) on the sample 1 where the focused electron beam is incident, and the vertical axis indicates the detected electron intensity as a relative value in arbitrary units (au). Figure 5A shows the case of a microscopy method that can extract internal magnetization information of the sample 1 by measuring the differential phase contrast, which is also called phase microscopy. In FIG. 5B, the horizontal axis indicates the point (x, y) on the sample 1 where the convergent electron beam is incident, and the vertical axis indicates the intensity of the integrated iDPC signal in a relative value in an arbitrary unit (au). That is, the vertical axis of FIG. 5B indicates I iDPC 5B shows the value of . The technique used in the embodiment of the present invention is a third technique for detecting magnetization information of the sample 1 using an electron beam, which is different from electron holography and Lorentz microscopy. The DPC data shown in FIG. 5A has a relatively large amount of noise, whereas the iDPC data shown in FIG. 5B has an improved signal-to-noise ratio.

[0053] The data processing device 20 calculates I represented by the above-mentioned equation (5) based on the magnetic flux density B(x, y, z) as the three-dimensional magnetization information data F(x, y, z) obtained as described above. iDPC For example, the iDPC data calculation unit 24 may include an iDPC data calculation unit 24 that measures the y-direction component B of the magnetic flux density B(x, y, z). y (x,y,z) and x-direction component B x By multiplying the data obtained by substituting (x, y, z) into each term on the right side of equation (5) (i.e., the data on the right side of equation (5)) by a predetermined constant, I iDPC The display device 31 may measure a vector I in the xyz coordinate space. iDPC An arrow representing

[0054] (Effects of the embodiment) According to the above-described embodiment, the sample 1 is irradiated with a convergent electron beam, and the electrons transmitted through the sample 1 are detected in the detection regions (for example, D1, D3 and D2, D4) on the opposite sides of the sample 1, and the intensity indicating the total amount of transmitted electrons is detected. The difference ΔI between these detected intensities is calculated by the difference acquisition unit 21, and based on the difference ΔI, the iDPC data (for example, I in the above formula (5)) is calculated as described above. iDPCThe value of ) can be obtained. As mentioned above, the signal-to-noise ratio of this iDPC data is improved. Therefore, it is possible to measure highly accurate magnetization information data. This makes it possible to obtain high-resolution images (e.g., three-dimensional images) that visualize the magnetization structure (electron spin structure) within the sample 1.

[0055] When a convergent electron beam is irradiated onto each scanning position (x, y) within a scanning region on the sample 1, the difference acquisition unit 21 calculates the above-mentioned difference ΔI for each scanning position (x, y), and the data measurement unit 22 measures the magnetization information data F(x, y) indicating the magnetization at the position (x, y) on the sample 1 based on the difference ΔI. In this way, F(x, y) used to obtain three-dimensional magnetization information inside the sample 1 can be obtained in a short time based on the difference ΔI. Therefore, the three-dimensional magnetization information data F(x, y, z) can be obtained by reconstruction processing with short data processing time.

[0056] The difference acquisition unit 21 calculates the difference ΔI between the detection intensities in the first and third detection areas D1 and D3 for each scanning position (x, y) as the x-direction difference I x The difference ΔI between the detection intensities in the second and fourth detection areas D2 and D4 is calculated as the y-direction difference I y In addition, the data measurement unit 22 calculates the x-direction difference I x The y-direction component of the magnetization information data F(x, y) is calculated based on the y The x-direction component of the magnetization information data is calculated based on the above equation, whereby the magnetization information data F(x, y) can be calculated as a vector.

[0057] Such magnetization information data F(x,y) may be, for example, magnetic flux density B(x,y) or vector potential A(x,y). Alternatively, the magnetization information data F(x,y) may be obtained by multiplying B(x,y) or A(x,y) by the thickness t of the sample 1 in the z direction.

[0058] The data measurement unit 22 measures two-dimensional magnetization information data F(x, y) relating to two-dimensional scanning positions (x, y) within the scanning region for each incident angle of the convergent electron beam on the sample 1. Furthermore, the reconstruction unit 23 reconstructs three-dimensional magnetization information data F(x, y, z) relating to the magnetization at each three-dimensional position (x, y, z) within the sample 1 based on the two-dimensional magnetization information data F(x, y) for each incident angle. This allows the magnetization information data F(x, y, z) and I to be reconstructed as a three-dimensional image that visualizes the magnetization structure (electron spin structure) within the sample 1. iDPC can be obtained with high accuracy in a short time.

[0059] (program) The data processing device 20 according to the above-described embodiment can be realized by a computer, a program, and a storage medium. In this case, the program causes the computer to execute the above-described processes of the data processing device 20 (e.g., the difference acquisition unit 21, the data measurement unit 22, the reconstruction unit 23, and the iDPC data calculation unit 24). In this case, the storage medium may be a computer-readable medium (e.g., a storage medium such as a computer hard disk or memory, or a CD-ROM) that non-temporarily stores the program. The computer reads and executes the program stored in the storage medium to realize each mechanism of the above-described data processing device 20 (e.g., the difference acquisition unit 21, the data measurement unit 22, the reconstruction unit 23, and the iDPC data calculation unit 24).

[0060] (Example) Using the above-described transmission electron microscope 10, information on the x and y components of the vector field inside the sample 1 was obtained while tilting the sample 1 about two orthogonal axes relative to the electron beam incident on the sample 1. Furthermore, based on the assumption that ∇·B=0 (where B is a vector, and this equation is expressed as ∂Bx / ∂x+∂By / ∂y+∂Bz / ∂z=0) holds (the leakage magnetic field of the entire system is zero), it is possible to calculate the z component of the vector field. The results are shown in Figures 6A to 6D.

[0061] Fig. 6A shows the calculation results for the triangular lattice structure of the skyrmion string. That is, Fig. 6A shows the three-dimensional magnetization information B(x, y, z) measured by the reconstruction unit 23 as described above.

[0062] Figures 6B and 6C show the distribution of the vector field on the top surface (Figure 6B) and at the center (Figure 6C) of the skyrmion string in Figure 6A. In Figures 6B and 6C, the horizontal direction is the x-direction, and the vertical direction is the y-direction. In Figures 6B and 6C, we can see that the magnetic field rotates in-plane, as indicated by the numerous black arrows added to Figure 6B.

[0063] Figure 6D shows the distribution of the longitudinal vector field of the skyrmion string of Figure 6A. In Figure 6D, each upward arrow indicates an upward magnetic field, and each downward arrow indicates a downward magnetic field.

[0064] Based on the magnetization information shown in FIGS. 6A to 6D, it is possible to extract magnetic field information about the skyrmion string and verify its structure.

[0065] The present invention is not limited to the above-described embodiment, and various modifications may be made within the scope of the technical concept of the present invention. For example, the data processing device 20 according to the embodiment of the present invention may not have all of the above-described features, or may have only some of the above-described features. [Explanation of symbols]

[0066] 1. Sample 1a surface 1b back side 10 Transmission electron microscope equipment 11 Electron beam irradiation device 11a Electron source 11b Lens Group 11b1 focusing lens 11b2 Objective lens 12 Control device 13 Detection equipment 13a Detector 13b Intensity detection unit 14 Drive unit 20 Data processing device 21 Difference acquisition part 22 Data measurement section 23 Reconstruction part 24 iDPC Data Calculation Department 31 Display device C center axis D1~D4 detection area

Claims

1. A data processing device that processes detection data of electrons transmitted through a sample by irradiating the sample with a convergent electron beam, the detection data includes, for each of detection regions located on opposite sides of the central axis of the convergent electron beam, a detection intensity indicating a total amount of electrons transmitted to the detection region; a difference acquisition unit that calculates a difference between the detection intensities of the detection regions opposite to each other; a data measurement unit that measures magnetization information data indicating magnetization information inside the sample based on the difference, Data processing device.

2. Two coordinate axes that intersect with each other when viewed from the direction of the central axis of the convergent electron beam are defined as an x-axis and a y-axis, a coordinate in the x-direction parallel to the x-axis is defined as x, and a coordinate in the y-direction parallel to the y-axis is defined as y, When a convergent electron beam is irradiated onto each scanning position (x, y) within a scanning region on the sample, the difference acquisition unit calculates, for each scanning position (x, y), a difference between the detection intensities of the detection regions opposite to each other based on the detection data obtained by irradiating the scanning position (x, y) with the convergent electron beam; the data measurement unit measures, for each scanning position (x, y), magnetization information data F(x, y) indicating magnetization at the position (x, y) in the sample based on the difference corresponding to the scanning position (x, y); 2. The data processing device according to claim 1.

3. the detection regions include first and third detection regions opposite each other in the x direction and second and fourth detection regions opposite each other in the y direction; the magnetization information data F(x, y) is vector data representing magnetization information at a position (x, y) in the sample, The difference acquisition unit calculates the difference ΔI between the detection intensities in the first and third detection regions for each scanning position (x, y) as an x-direction difference I ｘ and the difference ΔI between the detection intensities in the second and fourth detection regions is calculated as the y-direction difference I ｙ and The data measurement unit calculates the x-direction difference I ｘ The y-direction component of the magnetization information data F(x, y) is calculated based on the ｙ The x-direction component of the magnetization information data F(x, y) is calculated based on the 3. The data processing device according to claim 2.

4. the data measurement unit measures the two-dimensional magnetization information data F(x, y) related to the two-dimensional scanning position (x, y) within the scanning region for each incident angle of the convergent electron beam on the sample; the data processing device has a reconstruction unit that reconstructs three-dimensional magnetization information data F(x, y, z) related to magnetization at each three-dimensional position (x, y, z) in the sample based on the two-dimensional magnetization information data F(x, y) for each incident angle.

3. The data processing device according to claim 2.

5. 5. The data processing device according to claim 4, wherein the three-dimensional magnetization information data F(x, y, z) is a magnetic flux density or a vector potential of a magnetic field.

6. The three-dimensional magnetization information data F(x, y, z) is a magnetic flux density B(x, y, z), The integral data I is expressed by the following formula: ｉＤＰＣ An iDPC data calculation unit that calculates [Equation 5] Here, u ｘ is a unit vector in the x direction, and u ｙ is a unit vector in the y direction, e is the known charge of the electron, and h is Planck's constant.

5. The data processing device according to claim 4.

7. A data processing device according to any one of claims 1 to 6; an electron beam irradiation device that irradiates the sample with the convergent electron beam; a control device that controls scanning of a scanning region on the sample with the convergent electron beam; a detection device that detects electrons that have passed through the sample as a result of the irradiation and measures the detection data. Transmission electron microscope equipment.

8. A program for processing detection data of electrons transmitted through a sample by irradiating the sample with a convergent electron beam, the detection data includes, for each of detection regions located on opposite sides of the central axis of the convergent electron beam, a detection intensity indicating a total amount of electrons transmitted to the detection region; A process of calculating a difference between the detection intensities of the detection regions opposite to each other; and measuring magnetization information data indicating magnetization information inside the sample based on the difference. program.

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