An xrd detection method with sample longitudinal depth resolution

Abstract

This invention discloses an XRD detection method and apparatus with longitudinal depth resolution for samples. The method comprises: 1) For a sample to be tested, n X-rays of different energies are sequentially incident on the sample to obtain diffraction spectrum data corresponding to each energy of X-ray; wherein, according to the energy from smallest to largest, the wavelengths of the n different energies of X-rays are sequentially λ1 to λ2. n The penetration thickness of the sample is successively x1 to x n ;2) Obtain crystal structure information of samples at different wavelengths and calculate diffraction spectra;3) Wavelength λ i The corresponding diffraction pattern data minus the penetration thickness x i‑1 The corresponding wavelength λ i The diffraction data below were used to obtain the wavelength λ. i The corresponding X-ray penetration depth x of the sample i The diffraction pattern data at the location is used to calculate the sample depth x. i 4) Based on the obtained crystal structure information of each thickness layer, obtain the structural detection results of the sample with longitudinal depth resolution.

Description

Technical Field

[0001] This invention belongs to the field of X-ray crystal diffraction detection, specifically relating to an X-ray crystal diffraction detection method with longitudinal depth resolution of the sample. Background Technology

[0002] Since the discovery of X-rays in the late 19th century and X-ray crystallography (XRD) in the early 20th century, X-ray diffraction has made tremendous progress in the application of materials characterization. Its research directions cover a wide range of topics, including crystal structure, crystallinity, crystal phase, crystal defects, electron density, and stress distribution, and it has important applications in physics, chemistry, and engineering. XRD is a non-destructive, rapid qualitative and quantitative analysis method based on the property of a material's crystal energy to diffract X-rays. It involves studying diffraction patterns to determine the crystal structure, multi-component mixtures, and even stress distribution of materials.

[0003] Conventional XRD methods utilize crystal powder, which is ground into micron-sized or even smaller particles and flattened to form samples. Alternatively, samples cut directly from bulk materials can be used. When X-rays are incident on the crystal, diffraction beams are generated in directions different from the incident direction. The detector rotates to receive diffraction intensity data and the diffraction angle 2θ, ultimately producing a diffraction pattern that varies with the 2θ angle—the XRD spectrum. Bragg's law, 2dsinθ=nλ, can be used to simply explain crystal diffraction. It assumes that the incident wave undergoes specular reflection from parallel atomic planes within the crystal. When constructive interference occurs from the reflections from these planes, diffraction beams appear. Bragg's law reflects the relationship between the diffraction direction and the crystal structure. XRD methods can provide information such as phase analysis, lattice constant measurement, stress determination, and crystal defect detection, depending on the requirements.

[0004] In general, XRD methods only provide average information about the area of ​​the sample irradiated by the beam (which can be considered a volumetric region with a certain depth if necessary). Even with microbeam scanning technology, it only provides spatial resolution within the 2D scanning area, giving average structural information about the depth to which the incident X-rays can penetrate, but it lacks spatial resolution in the depth direction of the sample. Traditional XRD does not provide a good solution for internal conditions such as the depth of the sample. To study the different surface and depth properties of a sample, such as measuring the distribution of residual stress, methods such as chemical etching are usually used to peel off the surface layer by layer before XRD analysis to obtain structural information about the depth of the sample. Alternatively, high-energy X-ray or neutron diffraction methods can be used to bypass the surface layer of the material and obtain overall structural information about the material.

[0005] Given that conventional X-ray diffraction methods can only measure the sample surface, and peeling off the sample surface would damage the sample and involve complicated procedures, while neutron diffraction usually reflects the overall sample structure distribution, a non-destructive testing method that obtains crystal structure information at different locations on the sample surface and in depth is very valuable. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide an XRD detection method with a certain longitudinal depth resolution for samples. The main idea of ​​this invention is to utilize various X-ray wavelengths of different energies, taking advantage of the different depths into the sample by X-rays of different energies, and employing an analytical algorithm that performs differential iteration of the diffraction spectrum from the surface to the interior of the sample to measure the crystal structure information in the longitudinal direction of the sample.

[0007] This invention proposes a novel technical approach, utilizing the differences in the penetrating power of X-rays of different energies and subsequent data processing algorithms to obtain depth-resolved structural information of materials, thus achieving non-destructive testing of the longitudinal depth crystal structure distribution of samples. Simultaneously, this invention provides a new data processing and calculation method. It uses the lowest-energy X-ray diffraction data to fit the outermost sample structure, which is the initial condition for obtaining depth-resolved structural information. Then, it removes the contribution of the known outermost sample structure from the next lowest-energy X-ray diffraction data to obtain the subsurface structural information. This process is repeated to progressively obtain the structural information along the sample's depth.

[0008] The technical solution of this invention is as follows:

[0009] An XRD detection method with longitudinal depth resolution for samples, comprising the following steps:

[0010] 1) For a sample to be tested, n X-rays of different energies are sequentially incident on the sample to obtain the diffraction spectrum data of the sample corresponding to each energy of X-ray; wherein, according to the energy from smallest to largest, the wavelengths of the n different energies of X-rays are λ1~λ2. n The penetration thickness of the sample (defined as the X-ray intensity attenuation to e at normal incidence). -1 The depths from the material surface (multiples of the distance) are successively x1 to x2. n ;

[0011] 2) Based on the diffraction spectrum data corresponding to wavelength λ1, the crystal structure information of the sample penetration thickness x1 corresponding to wavelength λ1 can be calculated using the Rietveld full-spectrum fitting refinement method. Furthermore, based on the obtained crystal structure information of this thickness, the corresponding wavelength series λ2 to λ1 can be calculated. n Theoretical diffraction spectrum;

[0012] 3) Utilizing wavelength λ iThe corresponding diffraction pattern data minus the penetration thickness x i-1 The corresponding wavelength λ i The wavelength λ can be obtained from the calculated diffraction spectrum data. i The corresponding X-rays can penetrate to a depth x of the sample. i Diffraction pattern data at the location; calculate sample depth x based on diffraction pattern data. i Crystal structure information; i = 2 ~ n;

[0013] 4) Based on the crystal structure information of each thickness layer obtained in steps 2) and 3), the structural detection results of the sample with longitudinal depth resolution are obtained.

[0014] Furthermore, the detector receives the two-dimensional diffraction pattern generated after X-rays are incident on the sample; then, the diffraction spectrum I(2θ) in the range of 2θ is obtained based on the two-dimensional diffraction pattern; where 2θ is the angle between the incident X-ray and the diffracted X-ray.

[0015] Furthermore, the diffraction pattern corresponding to X-rays of wavelength λ incident on the sample. Where I0 is the X-ray beam intensity at wavelength λ, m is the electron mass, e is the electron charge, c is the speed of light, and N... c Let be the number of unit cells per unit volume of the sample, n be the multiplicity factor of the reflective surface of the sample, F(hkl) be the crystal structure factor of the sample, A(μ) be the absorption factor, μ be the absorption coefficient, and e be the absorption coefficient. -2M Here, x is the temperature factor, x is the penetration thickness, and s is the irradiated area.

[0016] An XRD detection device with longitudinal depth resolution for samples, characterized in that it includes:

[0017] X-ray source, used to provide X-rays of various energies;

[0018] A monochromator is used to monochromate the X-rays output from the X-ray source before they are incident on the sample to be tested; wherein, according to the energy from low to high, the wavelengths of the monochromated X-rays are successively λ1 to λ2. n ;

[0019] A slit or pinhole is used to limit the cross-sectional dimensions of the monochromator's output beam;

[0020] The sample adjustment stage is used to place the sample to be tested and to adjust the position and orientation of the sample.

[0021] An X-ray detector is used to receive the diffraction intensity distribution, i.e., the diffraction spectrum, produced after X-rays are incident on a sample.

[0022] The data processing unit is used for iterative analysis of the structural information of the sample's depth. Specifically, it calculates the penetration thickness x1 of the sample by the lowest energy X-ray at wavelength λ1, based on the diffraction spectrum data corresponding to wavelength λ1, and the crystal structure information corresponding to that thickness layer. Then, it uses the crystal structure information to inversely determine the sample at wavelength λ1 with penetration thickness x1. i The diffraction spectrum data is then used; then the wavelength λ is used. i The corresponding diffraction pattern data minus the thickness x i-1 The corresponding wavelength λ i The calculated diffraction spectrum data yields the result reflecting the wavelength λ. i The corresponding X-rays can penetrate to a depth x of the sample. i Material structure information at the location; based on x i The wavelength λ was calculated from the material structure information at that location. i The corresponding X-ray crystal structure information of the sample; i = 2 to n; then, based on the obtained crystal structure information of each thickness layer, the structural detection result of the sample with longitudinal depth resolution is obtained. However, existing measurements mostly use a single X-ray wavelength, and the sample information comes from the absorption thickness at this wavelength.

[0023] Compared with the prior art, the positive effects of the present invention are as follows:

[0024] This invention actively utilizes the ability of synchrotron radiation to select different wavelengths, adjusting the penetration depth according to the sample's absorption properties of X-rays at different energies to obtain material diffraction patterns with varying depths. Then, through iterative processing of the diffraction data, it reveals the crystal structure of the sample from the surface inwards, ultimately achieving a non-destructive, longitudinally depth-resolved XRD crystal structure analysis method. Previous measurements often used a single wavelength, with the absorption thickness at that wavelength determining the sample information. The method of this invention can help broaden longitudinal X-ray diffraction research, providing a testing method for non-destructive analysis of the crystal structure of samples from the surface inwards. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the method of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0027] The method of the present invention is as follows Figure 1 As shown, the device involved includes the following parts:

[0028] (1) X-ray source, which can provide X-rays of various energies;

[0029] (2) Monochromator, which can monochromate the X-ray source and select the monochromatic X-ray suitable for the test sample;

[0030] (3) Slits or pinholes, etc., to limit the cross-sectional dimensions of X-ray beams;

[0031] (4) Sample adjustment stage, used to place the sample to be tested and adjust the sample position and angle;

[0032] (5) X-ray detector, used to measure the distribution of diffraction intensity and angle from the sample (to obtain the diffraction spectrum);

[0033] (6) Iterative data processing algorithm for diffraction spectra of different energies (X-ray wavelengths) can obtain crystal structure information at different depths of the sample after data processing.

[0034] Since the main purpose of this invention is to solve the analysis of crystal structures with depth resolution in samples, general XRD detection methods and detection methods using microbeam scanning will not be discussed here. After an X-ray probe irradiates a sample, a detector can be used to record the overall or partial XRD signal of the sample diffraction—the diffraction spectrum.

[0035] By selecting the lowest energy X-ray from a series of different energies, and processing and fitting the X-ray diffraction data, the structural information of the outermost layer of the sample can be obtained. This is the starting point for obtaining depth-resolved structural information. For different samples and thicknesses, appropriate energies can be selected, and n X-rays of varying energies, from low to high, can be sequentially incident on the sample (e.g., ...). Figure 1 (As shown). Since the samples have different absorption coefficients μ for these X-rays, there is also a corresponding sample penetration thickness x. n By changing the X-ray wavelength (energy) and repeating the above detection, diffraction pattern data corresponding to the X-ray energy and from different sample thicknesses can be obtained. Due to the different X-ray wavelengths, even for the same sample with the same incident angle, the angular distribution of the diffraction pattern will differ. Each X-ray diffraction pattern data can yield structural information of the crystal within the sample corresponding to the incident depth of that X-ray energy. Only the diffraction pattern data of the lowest energy X-ray is a single, shallowest layer of sample crystal structure information. If the structure at the depth of the sample is not uniform, the diffraction pattern data of the next lowest energy X-ray is the sum of the intensities of the shallowest and deeper sample structures (for simplicity, we only assume the same thickness here). Because the crystal structure information of the shallowest sample has been determined by the diffraction data of the previous round of low-energy X-rays, the diffraction pattern of this layer of the sample for the next lowest energy X-rays can be calculated relatively accurately. Then, by removing this contribution from the overall experimental data, the remaining part is the diffraction data from the deeper layers of the sample, thus obtaining the structural information of the sample at that depth. By iteratively applying this method, we can obtain the diffraction patterns I(2θ) from different thickness layers of the sample corresponding to the wavelength.n 2θ is the diffraction angle, which is the angle between the incident X-ray and the diffracted X-ray. This diffraction data is stored in a computer for subsequent data analysis.

[0036] Data Analysis:

[0037] The detection data are analyzed using analytical algorithms. The spectral data obtained from n X-ray diffraction lines are fitted and refined to obtain the crystal structure analysis at different thickness locations. The specific steps are as follows:

[0038] (1) The sample is irradiated with low-energy X-rays of wavelength λ1, which can only penetrate a portion of the sample thickness x1. The two-dimensional diffraction pattern is received by a detector to obtain the diffraction spectrum I(2θ)1 in the 2θ range. The diffraction spectrum I(2θ)1 can reflect the material structure information of the thickness x1. The crystal structure information of the sample surface (i.e., the sample with a thickness of x1) is calculated by performing full-spectrum fitting using the Rietveld refinement method standard procedure (refer to Rietveld, Hugo M. "The Rietveld method." Physica Scripta 89.9 (2014): 098002.).

[0039] (2) Irradiate the sample with X-rays of wavelength λ2 (λ2 < λ1) using the same processing method as in (1) to obtain a diffraction pattern I(2θ)2 that penetrates deeper into the sample thickness x2 range. I(2θ)2 can be considered as the superposition of material diffraction patterns containing layer thickness x1 and layer thickness (x2 - x1). In X-ray diffraction theory, the cumulative intensity of sample diffraction can be expressed as...

[0040]

[0041] Where I0 is the X-ray beam intensity, m is the electron mass, e is the electron charge, c is the speed of light, λ is the X-ray wavelength, and N... c Where is the number of unit cells per unit volume, n is the multiplicity factor of the reflecting surface, F(hkl) is the structure factor of the crystal, A(μ) is the absorption factor, μ is the absorption coefficient, and e -2M denoted as temperature factor, x as penetration thickness, and s as irradiation area.

[0042] Using the full-spectrum fitting method, the X-ray diffraction spectrum of the sample with thickness x1 at wavelength λ2 can be calculated using the crystal structure parameters calculated by the above formula and (1). After removing the λ2 diffraction line fraction calculated based on the first layer material information from I(2θ)2, the diffraction spectrum data of the second layer thickness can be obtained. The crystal structure information of thickness (x2-x1) is calculated again using the Rietveld refinement method.

[0043] (3) Irradiate the sample with X-rays of wavelength λ3 (λ3 < λ2). The X-rays can penetrate to a deeper sample thickness x3. Using the same processing method as in (1), obtain the diffraction pattern I(2θ)3 within the sample thickness x3 range. I(2θ)3 can be considered as the superposition of material diffraction patterns containing layer thicknesses x1, (x2-x1), and (x3-x2). Using the same method as in (2), obtain the structural information of the first and second layers. After removing the contributions of the first and second layers to the overall spectrum from I(2θ)3, the diffraction pattern data of the third layer of the sample can be obtained. The crystal structure information of the third layer of the sample is calculated by the program.

[0044] (4) By following the above steps, diffraction information of arbitrary thickness and sample structure information of arbitrary thickness can be obtained.

[0045] Although specific embodiments of the invention have been disclosed for illustrative purposes to aid in understanding and implementing the invention, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the content disclosed in the preferred embodiments, and the scope of protection claimed by the invention is defined by the claims.

Claims

1. An XRD detection method with longitudinal depth resolution for samples, comprising the following steps: 1) For a sample to be tested, n X-rays of different energies are sequentially incident on the sample to obtain the measured diffraction spectrum data of the X-rays corresponding to each energy; wherein, according to the energy from smallest to largest, the wavelengths of the n different energies of the X-rays are as follows: λ 1~ λ n The penetration thickness of the sample is x1~x n The penetration thickness is the X-ray intensity attenuation at normal incidence. The depth of the material surface is twice the distance; 2) Based on wavelength λ The wavelength was calculated using the Rietveld full-spectrum fitting refinement method based on the measured diffraction spectrum data corresponding to 1. λ 1. The crystal structure information corresponding to the penetration thickness x1 of the sample is obtained, and based on the obtained crystal structure information of the penetration thickness x1, the corresponding wavelength series is calculated. λ 2~ λ n Theoretical diffraction spectrum; 3) Utilizing wavelength λ i The corresponding measured diffraction pattern data minus the penetration thickness x i-1 Corresponding wavelength λ i The theoretical diffraction spectrum data were used to obtain the wavelength. λ i The corresponding X-rays can penetrate to a depth x of the sample. i -x i-1 Actual diffraction pattern data at the location; calculate sample depth x based on actual diffraction pattern data. i -x i-1 Crystal structure information at location; i = 2 ~ n; 4) Based on the crystal structure information of each thickness layer obtained in steps 2) and 3), the structural detection results of the sample with longitudinal depth resolution are obtained.

2. The method according to claim 1, characterized in that, The detector receives the two-dimensional diffraction pattern generated after X-rays are incident on the sample; then, based on the two-dimensional diffraction pattern, the following is obtained: Diffraction patterns within the range ;in The angle between the incident X-ray and the diffracted X-ray.

3. The method according to claim 2, characterized in that, wavelength λ The diffraction pattern corresponding to the X-ray incident on the sample ;in, wavelength λ The X-ray beam intensity, m is the electron mass, e is the electron charge, and c is the speed of light. Let n be the number of unit cells per unit volume of the sample, and n be the multiplicity factor of the reflective surface of the sample. This is the crystal structure factor of the sample. As an absorption factor, The absorption coefficient is... denoted as temperature factor, x as penetration thickness, and s as irradiation area.

4. An XRD detection device with longitudinal depth resolution for samples, characterized in that, include X-ray source, used to provide X-rays of various energies; A monochromator is used to monochromate the X-rays output from the X-ray source before they are incident on the sample to be tested; wherein, according to the energy from low to high, the wavelengths of the monochromated X-rays are as follows: λ 1~ λ n ; A slit or pinhole is used to limit the cross-sectional dimensions of the beam output from the monochromator; The sample adjustment stage is used to place the sample to be tested and to adjust the position and angle of the sample. An X-ray detector is used to receive the diffraction intensity distribution, i.e., the diffraction spectrum, produced after X-rays are incident on a sample. The data processing unit is used to process the diffraction spectrum data based on the method described in claim 1 to obtain the structural detection results of the sample with longitudinal depth resolution.

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