Sample preparation and characterization method for angle-rotating crystal interface

Abstract

The invention discloses a sample preparation and characterization method of a rotation angle crystal interface, which is suitable for a sample with dislocation at the interface of two crystals, and comprises the steps of sample preparation and measurement of the relative rotation angle theta of the two crystals. A certain angle is formed between the cutting direction and the interface for sample preparation, a slice is taken out, and the obtained slice has three thin areas including a top material A crystal, a top material A / bottom material B crystal mixing area and a bottom material B crystal; measurement of the rotation angle theta: the electron beam direction is parallel to the rotation axis of the top sample during testing, and the rotation angle theta is directly measured by analyzing crystallographic information of the three thin areas. According to the method, the rotation angle of the top crystal relative to the bottom crystal can be accurately measured through TEM analysis of the three thin regions, and the error-tolerant rate of TEM sample preparation and analysis experiments is improved. In addition, the sample preparation technology can be used for monitoring the change of the physical properties of the sample in mechanics, thermotics, optics, electricity and the like along with the reduction of the size of the sample from the micron level to the nano level.

Description

Technical Field

[0001] The invention relates to the fields of electron microscopy, crystallography and sample preparation, and in particular to a method for preparing and characterizing a sample of a rotation angle crystal interface. Background Art

[0002] The atomic arrangement at the crystal interface determines the physical and chemical properties of the crystal composite material. Using an electron microscope (TEM), the crystallographic information of the crystal material can be directly observed and analyzed, including the arrangement of the bulk atoms, the types of atoms, and the bonding mode of the interface atoms. However, the relative rotation angle at the interface of two layers of crystal materials is often overlooked and lacks careful research. The schematic diagram of the relative rotation angle of the crystal interface is shown in Figure 1 shown.

[0003] Prior art 1: Solution introduction: The material to be tested is XS-TEM material, and the angle θ is measured by indirect measurement. When cutting the sample from the material to be tested, the overall shape of the sample must be perpendicular to the crystal interface during sample preparation and cutting (FIB Cut). Figure 2 As shown in (a), the TEM slice is taken out in a direction perpendicular to the material to be tested. At this time, the TEM slice obtained can retain the top crystal and bottom crystal of several μm size, which is suitable for analyzing bulk materials, such as Figure 2 (b) As shown in the figure. The relationship between the direction of the electron beam (E-beam) and the direction of the TEM slice during TEM testing is shown in the figure Figure 2 As shown in (c), the E-beam direction is perpendicular to the rotation axis of the top sample A. The rotation angle θ is estimated by analyzing the crystallographic information of the top crystal and the bottom crystal.

[0004] Test method: Analyze the crystallographic structural parameters of the top crystal and the bottom crystal respectively through TEM imaging (real space) or TEM electron diffraction (reciprocal space), including crystal form, lattice parameters, crystal orientation and crystal plane. The top crystal and the bottom crystal often have a rotation angle θ, and the above structural analysis needs to be achieved by tilting the TEM sample rod in the experiment. At the appropriate TEM sample rod tilt angle, image the top crystal, interface and bottom crystal at the same time. Estimate the rotation angle θ based on the analyzed crystallographic information. The appropriate TEM sample rod tilt angle is generally when the top crystal or the bottom crystal is in the positive band axis condition. The estimation of the rotation angle θ can be verified by the angle of the TEM sample rod rotation angle.

[0005] Disadvantages: 1. The rotation angle θ is calculated and measured indirectly, which is not accurate enough; 2. To verify θ by recording the tilt angle of the TEM sample rod, the direction and welding position of the FIB Cut sample and the placement of the TEM slice on the sample rod need to be carefully designed. The calibration and accuracy of the TEM goniometer also need to be considered.

[0006] Prior art 2: Solution introduction: The material to be tested is a conventional PVTEM material, and the angle θ is measured by direct measurement. Samples are cut from the material to be tested. When preparing the sample for cutting (FIB Cut), it is necessary to ensure that the overall shape of the sample is parallel to the crystal interface. Figure 3 As shown in (a), the TEM slice is taken out in a direction perpendicular to the material to be tested. At this time, most of the top and bottom crystals of the TEM slice are removed, and the interface is retained in a large area, as shown in Figure 3 (b) As shown in the figure. The relationship between the direction of the electron beam (E-beam) and the direction of the TEM slice during TEM testing is shown in the figure Figure 3 As shown in (c), the E-beam direction is parallel to the rotation axis of the top sample. By analyzing the crystallographic information of the top crystal and the bottom crystal, the rotation angle θ can be directly measured.

[0007] Test plan: 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, such as Figure 3 (c) is shown. The rotation angle θ is calculated by analyzing the electron diffraction pattern or the moiré fringe image. Since the TEM slice needs to be transparent to the electron beam and the thickness is generally tens to hundreds of nm, it is experimentally difficult to locate the interface during FIB Cut and retain the top and bottom crystals at the same time. Selecting a suitable sample area means that the area needs to have both top and bottom crystals.

[0008] Disadvantages: 1. The top and bottom crystals overlap, and it is difficult to analyze electron diffraction or moiré fringes. 2. It is difficult to prepare TEM samples with atomically flat interfaces. The interface position needs to be accurately located before FIB Cut, and the FIB stop space above and below the interface is tens of nanometers, or even several nanometers, which is difficult and has low fault tolerance. 3. When the thickness of the interface layer is greater than tens of nanometers, it is difficult to retain the top and bottom crystals at the same time when the TEM slice thickness is less than 100 nanometers. Summary of the invention

[0009] Based on the above statements, in order to meet the needs of analyzing the atomic structure of the crystal interface and the rotation angle 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 requirements of simple sample preparation and accurate measurement.

[0010] The technical solution of the present invention to solve the above technical problems is as follows: A method for sample preparation and characterization of a rotation angle crystal interface, which is applicable to samples with dislocation at the interface of two crystals, and includes steps of sample preparation and measurement of the relative rotation angle θ of the two crystals; The sample preparation is as follows: the cutting direction is at a certain angle to the interface to prepare the sample, and the thin slice is taken out, and the obtained thin slice has three thin areas: top material A crystal, top material A / bottom material B crystal mixed area, bottom material B crystal; The rotation angle θ is measured as follows: during the test, the direction of the electron beam is parallel to the rotation axis of the top sample, and the rotation angle θ is directly measured by analyzing the crystallographic information of the three thin regions.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, the above-mentioned sample preparation and characterization method of the 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.

[0013] 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.

[0014] 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 are analyzed through the high-resolution TEM image, electron diffraction pattern, and moiré fringe image, and the rotation angle θ is directly calculated.

[0015] Furthermore, in the above-mentioned sample preparation and characterization method of the angled 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.

[0016] 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.

[0017] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface is applicable to samples whose size increases continuously from nanoscale to micrometer scale, and is used to observe changes in the mechanical, thermal, optical, and electrical properties of the samples.

[0018] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-89°.

[0019] Preferably, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-30°.

[0020] Furthermore, in the above-mentioned method for preparing and characterizing samples of a rotation angle crystal interface, the rotation angle θ is 0.1-359.9°.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: The present invention proposes a method for sample preparation and characterization of a rotation angle crystal interface, which can be applied to all types of crystal interfaces, especially heterojunctions such as epitaxial or bonding process samples for accurate measurement of the crystallographic rotation angle. Through plane view (PV) TEM sample preparation, three thin areas of top crystal A, bottom crystal B, and A / B mixture can be obtained on the same TEM slice. Through TEM analysis of the three thin areas, the rotation angle of the top crystal relative to the bottom crystal can be accurately measured, and the error tolerance of TEM sample preparation and analysis experiments can be improved. In addition, by testing the mechanical, thermal, optical and electrical properties of the three thin areas, accurate physical property analysis of the film layer and the interface can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Background technology Prior art 1 is a schematic diagram of the structure of the crystal interface, wherein (a) is a schematic diagram of the cross-section of the crystal interface, and usually the top crystal material A has a rotation angle θ° relative to the bottom crystal material B, and (b) is a schematic diagram of the atomic structure of the interface from a top-down perspective, the left figure is the structure when the top crystal material A is rotated at an angle θ° = 0° relative to the bottom crystal material B (in order to solve the problem that the bottom crystal B is completely blocked and cannot be seen, it has one more row than the top crystal A), and the right figure is the structure when the top crystal material A is rotated counterclockwise at θ° ≠ 0° relative to the bottom crystal material B; Figure 2 1. Schematic diagram of cross-sectional XS-TEM sample preparation, TEM photography and angle analysis. The angle test using this method is an indirect test, and the angle plane is parallel to the direction of the TEM electron beam E-beam; Figure 3 Schematic diagram of conventional planar PVTEM sample preparation, TEM image taking and angle analysis in prior art 2. The angle test using this method is a direct test, and the angle plane is perpendicular to the direction of the TEM electron beam E-beam; Figure 4 A schematic diagram of angle plane PVTEM sample preparation, TEM imaging and angle analysis of a sample preparation and characterization method for an angle crystal interface provided by the present invention. The method is used to directly test the angle, and the angle plane is perpendicular to the direction of the TEM electron beam E-beam. In addition, three thin areas, namely the top crystal, the top and bottom mixed area, and the bottom crystal, can be obtained at the same time, thereby improving the analysis accuracy and fault tolerance of the angle. DETAILED DESCRIPTION

[0023] In order to facilitate understanding of the present application, the present application will be described more comprehensively 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.

[0024] 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 belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0025] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0026] A method for sample preparation and characterization of a rotation angle crystal interface, which is applicable to samples with dislocation at the interface of two crystals, and includes steps of sample preparation and measurement of the relative rotation angle θ of the two crystals; The sample preparation is as follows: the cutting direction is at a certain angle to the interface to prepare the sample, and the thin slice is taken out, and the obtained thin slice has three thin areas: top material A crystal, top material A / bottom material B crystal mixed area, bottom material B crystal; The rotation angle θ is measured as follows: during the test, the direction of the electron beam is parallel to the rotation axis of the top sample, and the rotation angle θ is directly measured by analyzing the crystallographic information of the three thin regions.

[0027] Based on the above technical solution, the present invention can also be improved as follows.

[0028] Furthermore, the above-mentioned sample preparation and characterization method of the 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.

[0029] 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.

[0030] 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: performing TEM imaging on the three thin areas respectively, including real space imaging and inverse space imaging, to obtain high-resolution TEM images, electron diffraction pattern images, and Moiré fringe images; analyzing the crystallographic information - lattice structure and crystal orientation through the high-resolution TEM images, electron diffraction patterns, and Moiré fringe images, and directly calculating the rotation angle θ.

[0031] Furthermore, in the above-mentioned sample preparation and characterization method of the angled 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.

[0032] 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.

[0033] Furthermore, the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface is applicable to samples whose size increases continuously from nanoscale to micrometer scale, and is used to observe changes in the mechanical, thermal, optical, and electrical properties of the samples.

[0034] Furthermore, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-89°.

[0035] Preferably, in the above-mentioned method for sample preparation and characterization of a rotation angle crystal interface, the certain angle is 0.1-30°.

[0036] Furthermore, in the above-mentioned method for preparing and characterizing samples of a rotation angle crystal interface, the rotation angle θ is 0.1-359.9°.

[0037] Example 1 The present invention provides a method for preparing and characterizing a sample of a rotation angle crystal interface, which can be used for preparing a rotation angle PVTEM sample and directly measuring the interface rotation angle θ. When preparing the sample, the cutting (FIB Cut) direction is 0.1-30° with 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. At this time, the TEM slice obtained 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 4 (b) As shown in the figure. The relationship between the direction of the electron beam (E-beam) and the direction of the TEM slice during TEM testing is shown in the figure 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 is directly measured. In addition, 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.

[0038] Sample preparation and calculation of rotation angle θ: 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).

[0039] 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.

[0040] 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.

[0041] Specifically, the sample structure prepared includes three thin regions, which include material A, material B and a mixed region of material A and material B.

[0042] 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.

[0043] 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.

[0044] The invention provides a method for sample preparation and characterization of a rotation angle crystal interface, which is applicable to all types of crystal interfaces.

[0045] 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.

[0046] The observation scale of the sample of the present invention increases continuously from the nanometer scale to the micrometer scale, and the physical properties such as mechanics, thermal, optical, and electrical properties change.

[0047] 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 principle of the present invention should be included in the protection scope 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 steps of the relative rotation angle θ of the two crystals; The sample preparation is as follows: the cutting direction is at a certain angle to the interface to prepare the sample, and the thin slice is taken out, and the obtained thin slice has three thin areas: top material A crystal, top material A / bottom material B crystal mixed area, bottom material B crystal; The rotation angle θ is measured as follows: during the test, the direction of the electron beam is parallel to the rotation axis of the top sample, and the rotation angle θ is directly measured by analyzing the crystallographic information of the three thin regions.

2. The method for sample preparation and characterization of a rotation angle crystal interface according to claim 1, characterized in that: The method 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 characteristics 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 areas is: taking TEM images of the three thin areas respectively, including real space imaging and inverse 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 0.1-89°.

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

10. 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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