A sample preparation and characterization method for a misfit crystal interface

Abstract

The application discloses a sample preparation and characterization method of a crystal interface with a rotation angle, which is suitable for a sample with dislocation at the interface of two crystals and comprises sample preparation and relative rotation angle θ measurement of the two crystals; the sample preparation is performed in a cutting direction with a certain angle with the interface to prepare the sample, the thin slice is taken out, and three thin areas of the thin slice are obtained, namely, a top material A crystal, a top material A / bottom material B crystal mixed area and a bottom material B crystal; the rotation angle θ measurement is performed by parallelizing the electron beam direction with the top sample rotation axis, and the rotation angle θ is directly measured by analyzing crystallographic information of the three thin areas. The method can accurately measure the rotation angle of the top crystal relative to the bottom crystal by TEM analysis of the three thin areas, and improves the fault tolerance of TEM sample preparation and analysis experiments. In addition, the sample preparation technology can be used for monitoring changes in physical properties of the sample, such as mechanics, heat, optics and electricity, with the size of the sample decreasing from microns to nanometers.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electron microscopy, crystallography and sample preparation, and in particular to a sample preparation and characterization method of a crystal interface with a relative rotation angle. BACKGROUND

[0002] The atomic arrangement of the crystal interface determines the physical and chemical properties of the crystal composite material. Transmission Electron Microscopy (TEM) can be used to directly observe and analyze the crystallographic information of the crystal material, including the arrangement of bulk atoms, the type of atoms and the bonding mode of interface atoms. However, the relative rotation angle at the interface of two-layer crystal materials is often ignored and lacks careful study. A schematic diagram of the relative rotation angle of the crystal interface is shown in Figure 1 .

[0003] Prior art 1:

[0004] Introduction of the scheme: the measured material is an XS-TEM material, and the measurement method of the rotation angle θ is indirect. The sample is cut from the measured material, and the sample preparation cut (FIB Cut) needs to ensure that the overall shape of the sample is perpendicular to the crystal interface as shown in Figure 2 (a), and the TEM lamella is perpendicular to the direction of the measured material. At this time, the TEM lamella can retain a few μm size of the top crystal and the bottom crystal, which is suitable for analyzing the bulk material as shown in Figure 2 (b). The relationship between the electron beam (E-beam) direction and the TEM lamella direction during TEM testing is shown in Figure 2 (c), and the E-beam direction is perpendicular to the rotation axis of the top sample A. By analyzing the crystallographic information of the top crystal and the bottom crystal, the rotation angle θ is calculated.

[0005] Test method: the crystallographic structure parameters of the top crystal and the bottom crystal are analyzed by TEM imaging (real space) or TEM electron diffraction (reciprocal space), including crystal type, lattice parameter, crystal direction and crystal plane. The top crystal and the bottom crystal often have a rotation angle θ, which needs to be realized by tilting the TEM sample rod in the experiment. At a suitable TEM sample rod tilt angle, the top crystal, the interface and the bottom crystal are imaged at the same time. By analyzing the crystallographic information, the rotation angle θ is estimated. The suitable TEM sample rod tilt angle is generally the top crystal or the bottom crystal in the positive zone axis condition. The estimation of the rotation angle θ can be verified by the angle of the TEM sample rod rotation angle.

[0006] Defects: 1, the angle θ is calculated and indirectly measured, the accuracy is insufficient; 2, the angle θ is verified by recording the TEM sample rod tilt angle, which needs to carefully design the FIB Cut sample direction and welding position, the TEM thin section placement position on the sample rod. And the calibration and accuracy of the TEM goniometer need to be considered.

[0007] Prior art 2:

[0008] Scheme introduction: the measured material is a conventional PVTEM material, and the measurement method of the angle θ is direct measurement. The sample is cut from the measured material, and the sample preparation cutting (FIB Cut) needs to ensure that the overall shape of the sample is parallel to the crystal interface, as shown in Figure 3 (a), the TEM thin section is taken along the direction perpendicular to the measured material. At this time, the top and bottom crystals of the TEM thin section are mostly cut off, and the interface is retained in a large area, as shown in Figure 3 (b). The relationship between the electron beam (E-beam) direction and the TEM thin section direction during TEM testing is as shown in Figure 3 (c), the E-beam direction is parallel to the top sample rotation axis. By analyzing the crystallographic information of the top and bottom crystals, the angle θ is directly measured.

[0009] Test scheme: select a suitable sample area for TEM electron diffraction experiment, and obtain the electron diffraction patterns of the top and bottom crystals at the same time, or use high-resolution TEM to obtain Moiré fringe images. The electron diffraction patterns of the top and bottom crystals will be superimposed at this time, as shown in Figure 3 (c). By analyzing the electron diffraction pattern or Moiré fringe image, the rotation angle θ is calculated. Since the TEM thin section needs to be electron beam transparent, the thickness is generally several tens of nanometers to several hundred nanometers, and the positioning of the interface during FIB Cut, and the simultaneous retention of the top and bottom crystals are very difficult in experiments. Selecting a suitable sample area means that the top and bottom crystals exist in this area.

[0010] Defects: 1, the top and bottom crystals are superimposed, and the analysis of electron diffraction or Moiré fringe is difficult. 2, under the condition of atomic-level flat interface, TEM sample preparation is difficult. Before FIB Cut, the interface position needs to be accurately positioned, and the FIB stop space on the interface is tens of nanometers, even several nanometer orders of magnitude, which is difficult and has low fault tolerance. 3, under the condition that the interface layer thickness is greater than several tens of nanometers, it is difficult to simultaneously retain the top and bottom crystals when the TEM thin section thickness is less than 100 nanometers. Summary

[0011] Based on the above statement, in order to meet the needs of analyzing the atomic structure of the crystal interface and the rotation angle analysis of the top crystal relative to the bottom crystal, it is necessary to develop a sample preparation and characterization method for the rotation angle crystal interface, which can meet the characteristics of simple sample preparation and accurate measurement.

[0012] The technical solution of the present invention to solve the above technical problems is as follows:

[0013] A method for sample preparation and characterization of a rotation angle crystal interface, applicable to samples with dislocation at the interface of two crystals, comprising steps of sample preparation and measurement of the relative rotation angle θ of the two crystals;

[0014] The sample preparation is as follows: the cutting direction is at a certain angle to the interface, and the thin slice is taken out. The obtained thin slice has three thin areas: top material A crystals, top material A / bottom material B crystal mixed area, and bottom material B crystals;

[0015] The rotation angle θ is measured by directing the electron beam in parallel with the rotation axis of the top sample during testing, and analyzing the crystallographic information of the three thin regions to directly measure the rotation angle θ.

[0016] On the basis of the above technical solution, the present invention can also be improved as follows.

[0017] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface also includes an analysis step, wherein the analysis step can achieve accurate physical property analysis of the film layer and the interface by testing the mechanical, thermal, optical and electrical properties of the three thin areas.

[0018] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the sample preparation method is FIB, mechanical grinding, pitting, argon ion beam polishing, or a combination of the above methods.

[0019] Furthermore, in the above-mentioned sample preparation and characterization method of the rotation angle crystal interface, the method for analyzing the crystallographic information of the three thin areas is: TEM images are taken on the three thin areas respectively, including real space imaging and reciprocal space imaging, to obtain high-resolution TEM images and electron diffraction pattern images; the crystallographic information - lattice structure and crystal orientation - is analyzed through the high-resolution TEM images, electron diffraction patterns, and moiré fringe images, and the rotation angle θ is directly calculated.

[0020] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the top material A / bottom material B crystal mixing zone includes an interface formed by the two materials and a mixing zone in which the thickness ratio of the two materials is continuously adjustable.

[0021] Furthermore, the above-mentioned sample preparation and characterization method of the angled crystal interface uses TEM (transmission electron microscopy), SEM (scanning electron microscopy), EBSD (electron backscatter diffraction), CBED (convergent beam electron diffraction) or Moire Pattern method when analyzing the crystallographic information of the three thin areas.

[0022] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface is applicable to sample sizes continuously increasing from nanometer scale to micrometer scale, and is used to observe changes in the mechanical, thermal, optical, and electrical properties of the sample.

[0023] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-89°.

[0024] Preferably, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-30°.

[0025] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the rotation angle θ is 0.1-359.9°.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0027] The present invention proposes a method for sample preparation and characterization of rotation-angle crystal interfaces that can be applied to all types of crystal interfaces, especially heterojunctions such as those obtained through epitaxial or bonding processes, to accurately measure the crystallographic rotation angles. Through planar view (PV) TEM sample preparation, three thin regions, a top crystal A, a bottom crystal B, and an A / B mixture, can be obtained on the same TEM slice. TEM analysis of the three thin regions accurately measures the rotation angle of the top crystal relative to the bottom crystal, and improves the error tolerance of TEM sample preparation and analysis experiments. Furthermore, by testing the mechanical, thermal, optical, and electrical properties of the three thin regions, accurate physical property analysis of the film layer and interface can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Background technology Prior art 1 schematic diagram of the structure of a crystal interface, where (a) is a cross-sectional schematic diagram of the crystal interface. Typically, the top crystal material A is rotated at an angle θ° relative to the bottom crystal material B. (b) is a schematic diagram of the atomic structure of the interface from a top-down perspective. The left figure shows the structure when the top crystal material A is rotated at an angle θ° = 0° relative to the bottom crystal material B (to address the problem of the bottom crystal B being completely blocked and therefore invisible, it has one more row than the top crystal A). The right figure shows the structure when the top crystal material A is rotated counterclockwise at θ° ≠ 0° relative to the bottom crystal material B.

[0029] Figure 2 Background technology Existing technology 1 Cross-sectional XS-TEM sample preparation, TEM imaging and angle analysis schematic diagram, the angle test using this method is an indirect test, the angle plane is parallel to the TEM electron beam E-beam direction;

[0030] Figure 3 Schematic diagram of conventional planar PVTEM sample preparation, TEM imaging and angle analysis in prior art 2. This method is used to test the angle directly, with the angle plane perpendicular to the direction of the TEM electron beam E-beam.

[0031] Figure 4 The present invention provides a method for sample preparation and characterization of angled crystal interfaces, which includes PVTEM sample preparation, TEM imaging, and angle analysis. This method uses direct testing of the angle, with the angle plane being perpendicular to the direction of the TEM electron beam E-beam. Furthermore, three thin regions, namely, the top crystal, the top and bottom mixed regions, and the bottom crystal, can be obtained simultaneously, thereby improving the analysis accuracy and fault tolerance of the angle. DETAILED DESCRIPTION

[0032] For ease of understanding of the present application, the present application will be described more fully below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0034] When used herein, the singular forms "a", "an", and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0035] A method for sample preparation and characterization of a rotation angle crystal interface, applicable to samples with dislocation at the interface of two crystals, comprising steps of sample preparation and measurement of the relative rotation angle θ of the two crystals;

[0036] The sample preparation is as follows: the cutting direction is at a certain angle to the interface, and the thin slice is taken out. The obtained thin slice has three thin areas: top material A crystals, top material A / bottom material B crystal mixed area, and bottom material B crystals;

[0037] The rotation angle θ is measured by directly measuring the rotation angle θ by analyzing the crystallographic information of the three thin regions while the electron beam direction is parallel to the rotation axis of the top sample during the test.

[0038] On the basis of the above technical solution, the present invention can also be improved as follows.

[0039] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface also includes an analysis step, wherein the analysis step can achieve accurate physical property analysis of the film layer and the interface by testing the mechanical, thermal, optical and electrical properties of the three thin areas.

[0040] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the sample preparation method is FIB, mechanical grinding, pitting, argon ion beam polishing, or a combination of the above methods.

[0041] Furthermore, in the above-mentioned sample preparation and characterization method of the rotation angle crystal interface, the method for analyzing the crystallographic information of the three thin areas is: TEM images are taken on the three thin areas respectively, including real space imaging and reciprocal space imaging, to obtain high-resolution TEM images, electron diffraction pattern images, and Moiré fringe images; the crystallographic information - lattice structure and crystal orientation - is analyzed through the high-resolution TEM images, electron diffraction patterns, and Moiré fringe images, and the rotation angle θ is directly calculated.

[0042] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the top material A / bottom material B crystal mixing zone includes an interface formed by the two materials and a mixing zone in which the thickness ratio of the two materials is continuously adjustable.

[0043] Furthermore, the above-mentioned sample preparation and characterization method of the angled crystal interface uses TEM (transmission electron microscopy), SEM (scanning electron microscopy), EBSD (electron backscatter diffraction), CBED (convergent beam electron diffraction) or Moire Pattern method when analyzing the crystallographic information of the three thin areas.

[0044] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface is applicable to sample sizes continuously increasing from nanometer scale to micrometer scale, and is used to observe changes in the mechanical, thermal, optical, and electrical properties of the sample.

[0045] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-89°.

[0046] Preferably, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-30°.

[0047] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the rotation angle θ is 0.1-359.9°.

[0048] Example 1

[0049] The present invention provides a method for sample preparation and characterization of a rotation angle crystal interface, which can be used for the preparation of rotation angle PVTEM samples and the direct measurement of the interface rotation angle θ. When preparing the sample, the cutting (FIB Cut) direction is 0.1-30° to the interface for sample preparation, such as Figure 4 As shown in (a), the TEM slice is taken out in a direction perpendicular to the sample to be tested. The TEM slice obtained at this time has three thin areas: the top material A crystal, the top material A / bottom material B crystal mixed area, and the bottom material B crystal, as shown in Figure 2. Figure 4 (b) As shown. The relationship between the direction of the electron beam (E-beam) and the direction of the TEM slice during TEM testing is as follows Figure 4 As shown in (c), the E-beam direction is parallel to the top sample rotation axis. By analyzing the crystallographic information of the three thin regions, the rotation angle θ can be directly measured. Furthermore, by testing the mechanical, thermal, optical, and electrical properties of the three thin regions, accurate physical analysis of the film and interface can be achieved.

[0050] Sample preparation and calculation of rotation angle θ:

[0051] The sample preparation methods include FIB, mechanical grinding, pitting, argon ion beam polishing, or a combination of several of these methods. The angled PVTEM samples were prepared by the above methods, such as Figure 4 As shown in (a~b).

[0052] TEM images were taken of the three thin areas, including real-space imaging and inverse-space imaging, to obtain high-resolution TEM images, electron diffraction pattern images, and moiré fringe images.

[0053] Crystallographic information - lattice structure and crystal orientation - is analyzed through high-resolution TEM images, electron diffraction pattern images, and Moiré fringe images, and the rotation angle θ is directly calculated.

[0054] Specifically, the prepared sample structure includes three thin regions, which include material A, material B, and a mixed region of materials A and B.

[0055] Specifically, the mixing zone of the above-mentioned materials A and B includes the interface between the two and a mixing zone in which the thickness ratio of the two materials is continuously adjustable.

[0056] Specifically, the sample preparation methods include FIB, mechanical grinding, pitting and argon ion beam polishing, including but not limited to the combination of the aforementioned methods.

[0057] The present invention proposes a method for sample preparation and characterization of rotation-angle crystal interfaces, which is applicable to all types of crystal interfaces.

[0058] The direct measurement method of the crystal interface angle of the present invention is not limited to the TEM method, and is also applicable to the measurement of the crystal interface angle by SEM, EBSD, CBED, and Moire Pattern methods.

[0059] The observation scale of the sample of the present invention is continuously increased from nanometer scale to micrometer scale, and the physical properties such as mechanical, thermal, optical, and electrical properties are changed.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for sample preparation and characterization of a rotation angle crystal interface, characterized in that: The method is applicable to samples with dislocation at the interface of two crystals, including sample preparation and measurement of the relative rotation angle θ of the two crystals; The sample preparation method includes cutting the sample at a certain angle to the interface, and then taking out the slice. The obtained slice has three thin areas: top material A crystals, top material A / bottom material B crystal mixed area, and bottom material B crystals. The certain angle is 0.1-89 degrees. The rotation angle θ is measured as follows: during the test, the direction of the electron beam is parallel to the crystallographic rotation axis of the top material A crystal, and the rotation angle θ is directly measured by analyzing the crystallographic information of the three thin areas respectively.

2. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The method further includes an analysis step, wherein the analysis step can achieve accurate physical property analysis of the film layer and the interface by testing the mechanical, thermal, optical and electrical properties of the three thin areas.

3. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The sample preparation method is FIB, mechanical grinding, pitting, argon ion beam polishing, or a combination of the above methods.

4. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The method for analyzing the crystallographic information of the three thin regions is as follows: performing TEM imaging on the three thin regions respectively, including real-space imaging and reciprocal-space imaging, to obtain high-resolution TEM images and electron diffraction pattern images; analyzing the crystallographic information - lattice structure and crystal orientation - through the high-resolution TEM images and electron diffraction patterns, and directly calculating the rotation angle θ.

5. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The top material A / bottom material B crystal mixing zone includes an interface formed by the two materials and a mixing zone in which the thickness ratio of the two materials is continuously adjustable.

6. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: When analyzing the crystallographic information of the three thin areas, TEM, SEM, EBSD, CBED or Moire Pattern method is used.

7. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The sample size applicable to this method increases continuously from nanoscale to micron scale, and is used to observe changes in the mechanical, thermal, optical, and electrical properties of the samples.

8. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The certain angle is 0.1-30°.

9. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The rotation angle θ is in the range of 0.1-359.9°.

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