System and method for generating TEM SADP images with high discrimination power

Abstract

It is an object of the present invention to provide a TEM SADP image generating system and method that adaptively responds to input parameters and has high discrimination power. [Means for solving the problem] The highly discriminating TEM SADP image generation system of the present invention is characterized by including a sample generation unit that generates a sample using at least one of the lattice constant, the relative positions of atoms in a unit lattice, and zone axis parameters, a vector generation unit that generates a reciprocal lattice vector corresponding to the unit lattice, a source generation unit that determines the brightness of the electron beam that will reach atoms in the generated sample, and a diffraction pattern generation unit that generates a virtual diffraction pattern image using the generated reciprocal lattice vector, the positions of atoms in the sample, and the determined brightness of the electron beam.

Description

[Technical Field]

[0001] The present invention relates to a system and method for generating TEM SADP images that adaptively responds to input parameters and has high discrimination power. [Background technology]

[0002] Previous techniques for generating TEM (Transmission Electron Microscope) SADP (Selected Area Diffraction Pattern) images either did not resemble the SADP captured by an actual TEM instrument or were time-consuming. In addition, there were problems with the SADP image generation process, such as ringing effects due to discontinuities in the light source, the inclusion of HOLZ (High Order Laue Zone) in the diffraction pattern, and the generation of diffraction patterns with blurred diffraction points.

[0003] For example, while the generated SADP image should be similar to the actual TEM SADP image shown in FIG. 1, SADP images generated by conventional techniques, such as virtual SADP images generated by the JEMS or Condor programs, contain HOLZ (higher order Laue zone) patterns as shown in FIG. 3, blurred diffraction spots as shown in FIG. 4, or ringing effects as shown in FIG. 5. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide a TEM SADP image generating system and method that adaptively responds to input parameters and has high discrimination power. The present invention also provides a system and method for generating virtual diffraction pattern images that can be used in a TEM. Furthermore, the present invention provides a technique that can prevent the phenomenon of ringing effects, HOLZ (higher order Laue zones), or blurred diffraction points from being included in a diffraction pattern image. Furthermore, the present invention provides a technique that can generate a diffraction pattern image by mathematically interpreting parameters input by a user. The present invention also provides a computing device that can perform high-speed processing by utilizing CPU parallel processing or GPGPU. Additionally, the present invention provides techniques that utilize image processing techniques such as gamma correction. Furthermore, the present invention provides a technique for utilizing SADP images generated adaptively in response to input parameters. An object of the present invention is to provide a technique that can prevent the phenomenon of material being destroyed by a large amount of scanning beam power. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the diffraction pattern image generation system of the present invention is characterized by including: a sample generation unit that generates a sample using at least one of a lattice constant, a relative position of atoms in a unit lattice, and a zone axis parameter; a vector generation unit that generates a reciprocal lattice vector corresponding to the unit lattice; a light source generation unit that calculates the brightness of an electron beam that will reach atoms in the generated sample; and a diffraction pattern generation unit that generates a virtual diffraction pattern image using the generated reciprocal lattice vector, the positions of atoms in the sample, and the calculated brightness of the electron beam.

[0006] The diffraction pattern image generating system of the present invention includes a sample generating unit that generates a slab-type sample using parameters input by a user, and a diffraction pattern generating unit that generates a diffraction pattern image using parameters acquired by analyzing the generated sample, wherein the sample generating unit adaptively determines the number of slab layers according to the lattice constant and zone axis parameters among the input parameters.

[0007] The diffraction pattern image generating system of the present invention includes a sample generating unit that generates a slab-shaped sample using parameters input by a user, a light source generating unit that determines the brightness of an electron beam that will reach atoms in the sample using the input light source shape and light source intensity, and a diffraction pattern generating unit that generates a virtual diffraction pattern image using the positions of atoms in the sample and the determined brightness of the electron beam. The light source shape and light source intensity are adaptively changed according to the input slab size or the size of the diffraction pattern image to prevent ringing effects in the diffraction pattern that may occur due to discontinuities in the light source.

[0008] In accordance with the present invention, there is provided a computer-readable recording medium having program code recorded thereon, the program code being used to perform a method including the steps of: generating a sample using at least one of a lattice constant, a relative position of atoms in a unit lattice, and a zone axis parameter; generating a reciprocal lattice vector that intersects with an Ewald sphere corresponding to the unit lattice; determining a brightness of an electron beam reaching atoms in the sample using an input light source shape and light source intensity; and generating a virtual diffraction pattern image using the generated reciprocal lattice vector, the relative position of atoms in the sample, and the determined brightness of the electron beam, wherein the diffraction pattern image is a TEM SADP image. [Effects of the Invention]

[0009] The TEM SADP image generating system and method according to the present invention adaptively responds to input parameters to prevent phenomena such as the inclusion of a High Order Laue Zone (HOLZ) in the diffraction pattern or the generation of a diffraction pattern with blurred diffraction points, and can prevent ringing effects in the diffraction pattern that can occur due to discontinuities in the light source. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of an actual TEM SADP image. [Figure 2] 1 is a diagram illustrating a virtual SADP image generated by the JEMS program. [Figure 3] 1 is a diagram illustrating an SADP image including a HOLZ (Higher Order Laue Zone) pattern. [Figure 4] 1 is a diagram illustrating an SADP image including a blurred diffraction spot pattern. [Figure 5] 1 is a diagram illustrating an SADP image including a ringing effect. [Figure 6] 1 is a block diagram illustrating a schematic configuration of a TEM SADP image generation system according to the present invention. [Figure 7] 1 is a diagram showing an SADP image in which ringing effects are eliminated, generated using the TEM SADP image generating method of the present invention; [Figure 8] 1 is a diagram illustrating an example of the lattice constant of a material belonging to a cubic system. [Figure 9] 1 is a diagram illustrating an example of the lattice constant of a material belonging to a hexagonal system. [Figure 10] 1 is a diagram illustrating the relationship between an electron beam, an Ewald sphere, a reciprocal lattice, and a diffraction pattern. [Figure 11] 1 is a diagram illustrating the unit cell before and after alignment. [Figure 12] 1 is a diagram illustrating the results of fabricating a slab-shaped sample using a unit cell aligned with the zone axis of the present invention. [Figure 13] 1 is a diagram illustrating an example of a diffraction pattern generated by the TEM SADP image generation system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] As used herein, singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "include" should not be interpreted as including all of the components or steps described in the specification, but should be interpreted as meaning that some components or steps may not be included, or that additional components or steps may be included. Furthermore, terms such as "unit," "module," etc. used in the specification refer to a unit that processes at least one function or operation, and may be implemented in hardware or software, or a combination of hardware and software.

[0012] The present invention relates to a system and method for generating a TEM (Transmission Electron Microscope) SADP (Selected Area Diffraction Pattern) image with high discrimination power by adaptively responding to input parameters. The system and method can generate a high-quality TEM SADP image with high discrimination power, free from the ringing effect of the diffraction pattern, which may occur due to discontinuities in the light source, the phenomenon in which a HOLZ (High Order Laue Zone) is included in the diffraction pattern, and the phenomenon in which a blurred diffraction point is included in the diffraction pattern.

[0013] To understand the characteristics of a material, an SADP image is acquired by scanning an electron beam on the material through a TEM. However, if the number of electron beam outputs is too many, the material may be damaged. Therefore, in order to prevent such damage to the material, the present invention can provide an SADP image by a program without scanning an actual electron beam. Therefore, the SADP image generated in this way can be used in various fields.

[0014] Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 6 is a block diagram illustrating the configuration of a TEM SADP image generating system according to an embodiment of the present invention, and FIG. 7 is a diagram illustrating an SADP image in which ringing effects are eliminated, generated using the TEM SADP image generating method according to the present invention. Referring to FIG. 6, the TEM SADP image generation system of this embodiment adaptively responds to input parameters and can generate SADP images that do not suffer from ringing effects in the diffraction pattern, phenomena in which HOLZ (higher-order Laue zone) is included in the diffraction pattern, and phenomena in which blurred diffraction points are included.

[0015] The TEM SADP image generating system may include a parameter setting unit 600, a sample generating unit 602, an HKL vector generating unit 604, a light source generating unit 606, a diffraction pattern generating unit 608, and a control unit (not shown) that controls the overall operation of these units. Here, the TEM SADP image generating system may be a single device, for example, a server, or may be commonly referred to as a computing device.

[0016] The parameter setting unit 600 can set parameters for generating an SADP image. For example, the parameter setting unit 600 can set parameters in response to a user input. According to one embodiment, the parameter setting unit 600 can set parameters such as a lattice constant, a relative position of atoms in a unit lattice, a zone axis, a wavelength and intensity of an electron beam, a camera distance, a size of a diffraction pattern image, etc. These parameters can be all input by a user, or other parameters can be automatically generated when the user inputs some of them.

[0017] The sample preparation unit 602 may prepare a slab-shaped sample using the relative positions of atoms within a unit cell and zone axis parameters. Here, the slab shape may refer to a thin plate shape. However, the sample to be prepared is not limited to a slab shape.

[0018] The HKL vector generator 604 can generate reciprocal lattice vectors that intersect with a virtual Ewald sphere. Here, the reciprocal lattice can be a parameter that is automatically generated by using a specific program according to the unit lattice set by the parameter setting unit 600.

[0019] The source generator 606 can calculate the relative brightness of the electron beam reaching each atom in the sample.

[0020] The diffraction pattern generator 608 can generate a virtual SADP image by accumulating diffractions generated in the interaction of all atoms and electrons contained in the sample. In this process, set parameters, such as reciprocal lattice vectors and relative brightness of the electron beam reaching the atoms, can be used.

[0021] In summary, the TEM SADP image generation system of this embodiment adaptively generates a virtual SADP image in response to various input parameters, and the SADP image can be free from ringing effects, the phenomenon in which a HOLZ (higher-order Laue zone) pattern is included in the diffraction pattern, and the phenomenon in which blurred diffraction points are included in the diffraction pattern. In addition, the TEM SADP image generation system can generate SADP images at high speed by utilizing parallel processing or GPGPU. That is, the TEM SADP image generation system can generate a large number of virtual SADP images at high speed, and the generated SADP images can be almost identical to the actual SADP images.

[0022] On the other hand, although the parameters input by the user are specifically mentioned, the parameters are not limited as long as the sample is generated using the parameters input by the user. That is, the TEM SADP image generation system includes a sample generation unit that generates a slab-shaped sample using parameters input by a user, a light source generation unit that determines the brightness of the electron beam that reaches atoms in the sample using the input light source shape and light source intensity, and a diffraction pattern generation unit that generates a virtual diffraction pattern image using the positions of atoms in the sample and the determined brightness of the electron beam.

[0023] Meanwhile, the reciprocal lattice vector, the brightness of the electron beam, and the diffraction pattern can be generated by mathematically applying parameters input by a user, which will be described in detail later. In addition, although the user inputs parameters to generate a TEM SADP image, parameters can be extracted from an actual SADP image and a virtual TEM SADP image can be generated using the extracted parameters. That is, the TEM SADP image generation system can generate multiple virtual TEM SADP images based on an actual SADP image. In addition, the number of slab layers, reciprocal lattice vector, and brightness of the electron beam are not fixed but can be adaptively changed according to parameters input by the user or parameters extracted from the actual SADP image, which will be described in detail later.

[0024] Hereinafter, the process of generating a TEM SADP image will be described in detail with reference to the accompanying drawings. Figure 8 is a diagram illustrating an example of the lattice constant of a material belonging to a cubic system. Figure 9 is a diagram illustrating an example of the lattice constant of a material belonging to a hexagonal system. Figure 10 is a diagram illustrating the relationship between an electron beam, an Ewald sphere, a reciprocal lattice, and a diffraction pattern. Figure 11 is a diagram illustrating the state before and after aligning a unit cell. Figure 12 is a diagram illustrating the results of fabricating a slab-shaped sample using a unit cell aligned with the zone axis according to an embodiment of the present invention. Figure 13 is a diagram illustrating an example of a diffraction pattern generated by the TEM SADP image generation system of the present invention.

[0025] The parameter setting unit 600 can set parameters such as the lattice constant, the relative positions of atoms in the unit cell, the zone axis, the wavelength and intensity of the electron beam, the camera distance, the size of the diffraction pattern image, etc. These parameters can be input by a user or extracted from an actual SADP image. In this case, the lattice constants and the relative positions of atoms in the unit lattice can be input in the form of a file such as CIF (Crystallography Information File), FHI-aims, or XYZ.

[0026] The sample generator 602 can generate a slab-shaped sample using the input parameters for the lattice constant, the relative positions of atoms in the unit lattice, and the zone axes. Specifically, the lattice constant can be composed of six variables: the magnitudes of the lattice vectors a, b, and c, and the angles α, β, and γ between the lattice vectors. If a=b=c, α=β=γ=90° as shown in Figure 8, the material belongs to the cubic crystal system, and if a=b≠c, α=β=90°, and γ=120° as shown in Figure 9, the material belongs to the hexagonal crystal system. The relative positions of atoms within a unit cell can be expressed as shown in Table 1 below, when the three-dimensional space within the unit cell is expressed between 0 and 1.

[0027] [Table 1]

[0028] The sample preparation unit 602 may align the unit lattice so that the lattice plane corresponding to the direction of the electron beam and the zone axis is perpendicular to each other, as shown in FIG. 11, to produce a slab-shaped sample as shown in FIG. 12. Here, a slab-shaped sample may refer to a structure in which unit lattices are arranged in a plate-like manner. While a cubic crystalline material is prepared in FIG. 12, a hexagonal crystalline sample may also be prepared in the same manner. In this case, the Rodrigues formula may be used to align the direction of the electron beam, which can be expressed as a three-dimensional vector, with the zone axis.

[0029] According to one embodiment, the number of slab layers is adaptively determined according to the input lattice constant and zone axis parameters, thereby preventing the phenomenon of HOLZ (higher-order Laue zone) being included in the diffraction pattern and the phenomenon of a diffraction pattern with blurred diffraction points being generated. That is, the sample preparation unit 602 can adaptively determine the number of slab layers according to the input lattice constant and zone axis parameters to prevent the phenomenon of HOLZ (higher-order Laue zone) being included in the diffraction pattern or the generation of a diffraction pattern with blurred diffraction points. The unit lattice can be aligned in the slab layers determined in this way. As a result, even for the same material, the number of slab layers can vary depending on the parameters input by the user.

[0030] The HKL vector generator 604 can generate reciprocal lattice vectors that intersect with a virtual Ewald sphere, as shown in Fig. 10. Diffraction can occur at the reciprocal lattice that intersects with the Ewald sphere, and thus the reciprocal lattice at which diffraction occurs can be detected to obtain a diffraction pattern. Here, the reciprocal lattice can be a parameter that is automatically generated by using a specific program or formula according to the unit lattice set by the parameter setting unit 600. Specifically, the HKL vector generator 604 can calculate reciprocal lattice vectors h(x,y), k(x,y), and l(x,y) using the image coordinates (x,y) spaced a predetermined distance (d) from the origin where the electron beam is located and the wavelength (λ) of the electron beam using the following Equations 1 and 2.

[0031]

number

[0032]

number

[0033] As shown in Equation 1, χ can be calculated by knowing the image coordinates (x, y), wavelength (λ), and the distance (d) from the origin where the electron beam is located. Using the calculated χ, the reciprocal lattice vectors [h(x, y), k(x, y), l(x, y)] can be automatically calculated.

[0034] The light source generating unit 606 receives the shape and intensity of the light source as input and calculates the brightness of the electron beam reaching each atom in the sample. In this case, the shape of the light source may be flat or have a 2D Gaussian shape based on a lattice plane perpendicular to the direction of the electron beam.

[0035] The three-dimensional position of an atom in the sample is (x j ,y j ,z j ), assuming a flat light source, the brightness of the electron beam reaching each atom is given by the following equation 3:

[0036]

number

[0037] Assuming a 2D Gaussian source configuration, the brightness of the electron beam reaching each atom is given by Equation 4 below.

[0038]

number

[0039] Assuming a 3D Gaussian light source configuration, the brightness of the electron beam reaching each atom is given by Equation 5 below.

[0040]

number

[0041] The light source generating unit 606 can utilize a 3D Gaussian to create a continuous light source shape. In this case, the 3σ of the Gaussian can be set smaller than the width, length, and height of the sample to prevent discontinuities from occurring at the edge of the sample.

[0042] According to another embodiment, the light source generating unit 606 may simultaneously utilize a two-dimensional Gaussian and an exponential decay function, removing discontinuities that may occur in the horizontal and vertical directions of the sample using the two-dimensional Gaussian, and removing discontinuities that may occur in the height direction of the sample using the exponential decay function.

[0043] Meanwhile, the brightness of the electron beam can be simulated by applying exponential decay to the direction of the electron beam. The light source to which exponential decay is applied can be defined as Equation 6 below.

[0044]

number

[0045] The size and shape of the light source generated by the light source generating unit 606 can be adaptively changed depending on the size of the input slab and the size of the diffraction pattern image, etc., and as a result, it is possible to prevent the ringing effect of the diffraction pattern that may occur due to discontinuities in the light source, as shown in Figure 7. That is, the light source generating unit 606 can adaptively change the size and shape of the light source depending on the size of the input slab and the size of the diffraction pattern image to prevent the ringing effect of the diffraction pattern.

[0046] The diffraction pattern generating unit 608 generates a diffraction pattern based on the reciprocal lattice vectors [h(x, y), k(x, y), l(x, y)] obtained by the HKL vector generating unit 604, the positions of atoms in the sample, and the brightness (I(x j ,y j ,z j )), the accumulated diffraction pattern (F(h,k,l)) can be calculated as shown in Equation 7 below.

[0047]

number

[0048] Then, the diffraction pattern generating unit 608 calculates the maximum value of the accumulated diffraction pattern, and linearly normalizes the accumulated diffraction pattern based on the calculated maximum value to generate a diffraction pattern image. According to another embodiment, the diffraction pattern generator 608 may generate a diffraction pattern image by nonlinearly normalizing the image using an image processing technique such as gamma correction. In this case, the diffraction pattern generator 608 can independently calculate the diffraction generated by the interaction of each atom and electron in the sample, allowing for high-speed calculations using CPU parallel processing or a general-purpose computing on graphics processing unit (GPGPU). The SADP image generated in this manner is shown in FIG. 13. As shown in FIG. 13, the SADP image does not exhibit ringing effects, phenomena in which higher-order Laue zones (HOLZs) are included in the diffraction pattern, or diffraction patterns with blurred diffraction points. Meanwhile, the diffraction pattern generator 608 can apply various functions to the accumulated diffraction values ​​to generate an SADP image. For example, the diffraction pattern generator 608 can apply a linear function to generate a diffraction pattern, and Vo=AVi γ The diffraction pattern can also be generated using a function used in gamma correction, such as:

[0049] In summary, the SADP image generation system of this embodiment can generate an SADP image that prevents the ringing effect, the phenomenon in which HOLZ (higher-order Laue zone) is included in the diffraction pattern, and the phenomenon in which a diffraction pattern with blurred diffraction points is generated, by using the reciprocal lattice vector, the position of atoms in the sample, and the brightness of the electron beam.

[0050] Meanwhile, the components of the above-described embodiments can be easily understood from a process perspective, i.e., each component can be understood as a respective process, and the processes of the above-described embodiments can be easily understood from the perspective of device components.

[0051] Furthermore, the above-described technical content may be embodied in the form of program instructions that can be executed by various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiments, or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program instructions, such as ROMs, RAMs, and flash memories. Examples of program instructions include not only machine language code, such as that produced by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc. A hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, or vice versa.

[0052] The above-described embodiments of the present invention have been disclosed for illustrative purposes, and those skilled in the art having ordinary skill in the art may make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following claims.

Claims

1. a sample preparation unit that prepares a sample using at least one of a lattice constant, a relative position of atoms in a unit lattice, and a zone axis parameter; a vector generation unit that generates a reciprocal lattice vector corresponding to the unit lattice; a light source generating unit for determining the brightness of the generated electron beam that reaches atoms in the sample; a diffraction pattern generator that generates a virtual diffraction pattern image using the generated reciprocal lattice vectors, the positions of atoms in the sample, and the brightness of the electron beam that has been determined; the diffraction pattern generating unit calculates an accumulated diffraction pattern using the generated reciprocal lattice vectors, positions of atoms in the sample, and the determined brightness of the electron beam; calculates a maximum value of the accumulated diffraction pattern; and nonlinearly normalizes the accumulated diffraction pattern using an image processing technique that uses gamma correction based on the calculated maximum value to generate the diffraction pattern image.

2. a parameter setting unit for setting the lattice constant, the relative positions of atoms in the unit lattice, the zone axis parameters, the wavelength of the electron beam, and the size of the diffraction pattern image; The diffraction pattern image generating system of claim 1 , wherein the parameters set by the parameter setting unit are input by a user.

3. 2. The diffraction pattern image generating system of claim 1, wherein the diffraction pattern image is a Transmission Electron Microscope (TEM) Selected Area Diffraction Pattern (SADP) image.

4. 4. The diffraction pattern image generating system of claim 3, wherein the sample generating unit generates a slab-shaped sample by arranging the unit lattices so that the direction of the zone axis and a lattice plane corresponding to the zone axis are perpendicular to each other.

5. the sample preparation unit prepares a sample in a slab form, and determines the number of layers of the slab according to the lattice constant and the zone axis parameter; 5. The diffraction pattern image generating system of claim 4, wherein when the determined number of layers of the slab is used, the generated diffraction pattern image does not include a HOLZ (High Order Laue Zone) or a diffraction pattern with blurred diffraction points is not generated.

6. 6. The diffraction pattern image generating system of claim 5, wherein the number of layers of the slab is determined taking into consideration the amount of calculation that increases in a subsequent diffraction pattern calculation process as the size of the slab increases.

7. 2. The diffraction pattern image generating system of claim 1, wherein the vector generating unit generates a reciprocal lattice vector intersecting with an Ewald sphere using an image coordinate spaced a predetermined distance from an origin where the electron beam is located and a wavelength of the electron beam.

8. 2. The diffraction pattern image generating system of claim 1, wherein the light source generating unit determines the brightness of the electron beam reaching the atoms in the sample using the input light source type and light source intensity.

9. The shape and intensity of the light source are variable depending on the size of the input slab and the size of the diffraction pattern image; 10. The diffraction pattern image generating system of claim 8, wherein when the shape and intensity of the variable light source are used, ringing effects of the diffraction pattern that may occur from discontinuities in the light source do not occur in the diffraction pattern image.

10. The diffraction pattern image generating system described in Claim 3, characterized in that the diffraction pattern generating unit uses gamma correction on the diffraction pattern image to convert low-brightness diffraction points contained in the diffraction pattern image so that they are more visible.

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