A PPC film and preparation method for preparing TEM samples by dry method spot transfer

Abstract

The present invention discloses a PPC film and a preparation method for preparing TEM samples by dry method point transfer. By using a special PPC film, the target material is non-destructively transferred to a copper mesh to complete the preparation of the TEM sample, avoiding the problems of random distribution of the target sample, large material damage, and inability to transfer water-prone oxygen samples in wet transfer, thereby achieving efficient and reliable preparation of high-quality TEM samples. By using the physical properties of PPC, with the assistance of a micro-area transfer platform, the target sample can be precisely operated in a micro-area at a fixed point. This new method does not require the use of strong acids and alkalis for corrosion, and the material and carbon film will not be damaged during the transfer process. The process is suitable for different types of materials, including thin film materials, two-dimensional materials, nanowires, etc. The advantages of the present invention are precise point transfer, no water contact, little sample damage, little organic residue, wide application, low cost, high efficiency, and high success rate.

Description

Technical Field

[0001] The invention relates to a method for preparing a TEM sample based on PPC dry transfer, and in particular to a method for preparing a TEM sample quickly, efficiently and without damage. Background Art

[0002] With the development of compound semiconductor technology, various material characterization technologies are becoming more and more perfect, especially the characterization technology represented by transmission electron microscopy is of great significance in the analysis of semiconductor materials. Analyzing the influence of microscopic defects of semiconductor materials on device performance has important guiding significance for optimizing crystal growth process and improving device performance. Transmission electron microscopy (TEM) is a high-resolution electron microscope with atomic-scale resolution. It can characterize the microstructure of materials at the nano and atomic scales, and can provide information on microscopic defects, chemical composition, lattice structure and material quality. It is an important means to link sample structure with performance, and has attracted much attention in the development of optoelectronic functional materials and devices.

[0003] Among them, high-quality sample preparation is a very important part of TEM analysis technology. However, the currently commonly used wet transfer method for preparing samples not only has a very low success rate but is also not suitable for samples that are easily oxidized by water. During the transfer process, the samples are randomly distributed on the copper mesh, making it impossible to achieve accurate transfer. In addition, traditional wet transfer requires hydrofluoric acid corrosion, which seriously affects the quality of the samples.

[0004] In order to solve the above problems, the present invention proposes a novel PPC (polypropylene carbonate) dry transfer method. The PPC film has unique physical properties, a glass temperature of 25-45°C, a melting temperature of 120°C, and is easily soluble in acetone. With the assistance of a micro-area transfer platform, the target material can be micro-operated at a fixed point. The material and the carbon film will not be damaged during the transfer process. While ensuring the quality of the material, it has the characteristics of fast, efficient and simple operation, which greatly shortens the sample preparation cycle. Summary of the invention

[0005] The present invention provides a PPC film and a preparation method for preparing TEM samples by dry method spot transfer. The PPC film has unique physical properties, can transfer the target material to a copper mesh without loss, and realize micro-area spot operation, making the preparation of TEM samples more efficient.

[0006] A PPC film for preparing TEM samples by dry method spot transfer comprises a glass slide 1, a PDMS film 2, a transparent tape 3, a PPC film 4, and a transparent tape 5 with a middle hole. The structure of the PPC film is as follows: the PDMS film 2 is fixed on the glass slide 1 by the transparent tape 3, the transparent tape 5 with a middle hole on which the PPC film 4 is adhered is adhered to the transparent tape 3, and the PPC film 4 is located at the opening position of the transparent tape with a middle hole;

[0007] The glass slide 1 is a medical glass slide;

[0008] The PDMS film 2 has a size of 0.3×0.3 cm and a thickness of 0.3 cm;

[0009] The transparent tape 3 is a single-sided transparent tape;

[0010] The PPC film 4 has a size of 1×1 cm and a thickness of 200 nm;

[0011] The transparent tape 5 with a hole in the middle is a single-sided transparent tape, and the size of the hole is 0.5×0.5 cm.

[0012] A PPC film and preparation method for preparing TEM samples by dry method spot transfer, the preparation steps of the PPC film are as follows:

[0013] Step 1: Prepare PPC solution. Dissolve 4.5g of PPC plastic in 30mL of anisole; place the prepared solution on a magnetic stirrer and stir at 90℃ for 2h; spin coat the prepared solution (500r / min 5s; 1000r / min 60s; 8000r / min 1s) on a SiO2 substrate; dry at 90℃ for 10min to form a PPC film;

[0014] Step 2: Prepare the PPC film. Mix PDMS plastic and 18B glue at a ratio of 15:1; dry in a vacuum oven at 120°C for 1 hour; cut a small piece of the solidified PDMS and place it in the middle of a glass slide; fix the PDMS on the glass slide with transparent tape; use a transparent tape with holes to stick the PPC film from the SiO2 substrate, with the holes of the tape aligned with the center of the PPC film; cover the stuck PPC film on the transparent tape so that the PPC film is lifted up by the raised PDMS film; bake at 120°C for 2 minutes to make the surface of the PPC film flat, and the preparation of the PPC film is completed.

[0015] A PPC film and preparation method for preparing TEM samples by dry method spot transfer, the preparation steps of TEM samples are as follows:

[0016] Step 1: PPC film adheres sample material at a fixed point. Prepare the sample material onto the SiO2 substrate by mechanical stripping; place the substrate with sample material on the base of the transfer platform; find the target sample material under the microscope on the transfer platform; with the help of the transfer platform, gently press the prepared PPC film onto the sample material; heat the base of the sample stage to 45°C to soften the PPC film and tightly adsorb the sample material, then cool it to room temperature; gently lift the glass slide with the robotic arm, and the sample will be adhered to the PPC film; repeat this process until the sample is adhered by the PPC film.

[0017] Step 2: Transfer the sample to the copper mesh. Place the PDMS film on the SiO2 substrate; place the copper mesh in the middle of the PDMS and place it on the base of the transfer platform; under the microscope of the transfer platform, use the robotic arm to gently press the PPC film with the sample material adhered to the carbon film of the copper mesh; heat the base of the transfer platform to 120°C to make the melted PPC film stick tightly to the carbon film; after 5 minutes, slowly lift the glass slide, and the sample material and the melted PPC film will adhere to the copper mesh together; this process can be repeated until the sample material adheres to the copper mesh.

[0018] Step 3: Dissolve the PPC film and complete the TEM sample preparation. Place the copper mesh with the sample material and the substrate in a glass container and soak them in acetone for 10 minutes. The PPC film and PDMS film will be dissolved, while the sample material will adhere to the copper mesh. After gently blowing it dry with an air gun, the TEM sample preparation is completed.

[0019] The advantages of this patent are:

[0020] Different from the traditional wet transfer, the present invention uses a new PPC film-assisted dry method spot transfer technology, which solves the problems of random sample distribution, large damage, and inability to transfer water-prone and oxygen-prone samples in wet transfer. The operation process is simple and safe, which greatly improves the efficiency and success rate of sample preparation. At the same time, the transfer process will not damage the material and copper mesh, and there is little organic residue, which realizes efficient and accurate preparation of TEM samples. The scope of application of this process includes most sample materials including thin film materials, two-dimensional materials, nanowires and water-prone and oxygen-prone materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the PPC membrane structure; Figure 1 Middle: 1 glass slide, 2 PDMS film, 3 transparent tape, 4 PPC film, 5 transparent tape with a hole in the middle.

[0022] Figure 2 This is a flow chart of the PPC drying method for spot transfer preparation of TEM samples.

[0023] Figure 3The following is a schematic diagram of the completed TEM sample structure, where Figure (1) is a cross-sectional view and Figure (2) is a top view. DETAILED DESCRIPTION

[0024] The following is a detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the following implementation. The accompanying drawings use non-precise ratios and simplified forms, and are only used to conveniently and clearly assist in explaining the specific processes and operating procedures of the embodiments of the present invention.

[0025] 1. Please refer to Figure 1 , Figure 1 The figure shows the structure of the PPC membrane. 1 is a glass slide.

[0026] 2 is a PDMS film, 3 is a transparent tape, 4 is a PPC film, and 5 is a transparent tape with a hole in the middle.

[0027] 2. Please refer to Figure 2 , Figure 2 The figure shows the flow chart of preparing TEM samples by PPC dry method spot transfer, including the following processes:

[0028] Step 1: Prepare PPC solution. Dissolve 4.5g of PPC plastic in 30mL of anisole; place the prepared solution on a magnetic stirrer and stir at 90℃ for 2h; spin coat the prepared solution (500r / min 5s; 1000r / min 60s; 8000r / min 1s) on a SiO2 substrate; dry at 90℃ for 10min to form a PPC film;

[0029] Step 2: Prepare PPC film. Mix PDMS plastic and 18B glue in a ratio of 15:1; dry in a vacuum oven at 120℃ for 1h; cut a small piece of solidified PDMS and place it in the middle of a glass slide; fix PDMS on the glass slide with transparent tape; use transparent tape with holes to stick the PPC film from the SiO2 substrate, with the holes of the tape aligned with the center of the PPC film; cover the stuck PPC film on the transparent tape so that the PPC film is lifted up by the raised PDMS film; bake at 120℃ for 2min to make the surface of the PPC film flat, and the preparation of the PPC film is completed.

[0030] Step 3: PPC film adheres sample material at a fixed point. Prepare the sample material onto the SiO2 substrate by mechanical stripping; place the substrate with the sample material on the base of the transfer platform; find the target sample material under the microscope on the transfer platform; with the help of the transfer platform, gently press the prepared PPC film onto the sample material; heat the base of the sample stage to 45°C to soften the PPC film and tightly adsorb the sample material, then cool it to room temperature; gently lift the glass slide with the robotic arm, and the sample will be adhered to the PPC film; repeat this process until the sample is adhered by the PPC film.

[0031] Step 4: Transfer the sample to the copper mesh. Place the PDMS film on the SiO2 substrate; place the copper mesh in the middle of the PDMS and place it on the base of the transfer platform; under the microscope of the transfer platform, use the robotic arm to gently press the PPC film with the sample material adhered to the carbon film of the copper mesh; heat the base of the transfer platform to 120°C to make the melted PPC film stick tightly to the carbon film; after 5 minutes, slowly lift the glass slide, and the sample material and the melted PPC film will adhere to the copper mesh together; this process can be repeated until the sample material adheres to the copper mesh.

[0032] Step 5: Dissolve the PPC film and complete the TEM sample preparation. Place the copper mesh with the sample material and the substrate in a glass container and soak them in acetone for 10 minutes. The PPC film and PDMS film will be dissolved, while the sample material will adhere to the copper mesh. After gently blowing it dry with an air gun, the TEM sample preparation is completed.

[0033] The sample material described in the steps can be a thin film material, a two-dimensional material, or a nanowire. It can be torn off the SiO2 substrate by a mechanical stripping method, or grown on the SiO2 substrate by a growth process. It can be a sample that is easily oxidized by water, and the material thickness can be from nanometers to micrometers.

[0034] The SiO2 substrate described in the step has a size of 1×1 cm;

[0035] The PPC film described in the step, the PPC film glass transition temperature ( T g) between 25 and 45°C, with a melting point of 120°C, and easily soluble in acetone;

[0036] The transparent tape with a hole in the middle as described in the step has a hole size of 0.5×0.5 cm, which is used to stick the PPC on the substrate and stick it to the glass slide;

[0037] The PDMS film described in the step is easily soluble in acetone, has a size of 0.3×0.3 cm, and a thickness of 0.3 cm, and its purpose is to lift up the PPC film;

[0038] The glass slide described in the step is a medical glass slide;

[0039] The sample material described in the steps can be a thin film material, a two-dimensional material, or a nanowire. It can be torn off the SiO2 substrate by a mechanical stripping method, or grown on the SiO2 substrate by a growth process. It can be a sample that is easily oxidized by water, and the material thickness can be from nanometers to micrometers.

[0040] The copper mesh described in the steps is a copper mesh specially used for TEM testing, and has a fragile carbon film on it;

[0041] The PDMS membrane on the SiO2 substrate described in the step has a size of 1×1 cm and a thickness of 1 mm, and its purpose is to fix the copper mesh;

[0042] Please refer to Figure 3 , Figure 3 The figure shows the completed TEM sample, where (1) is a cross-sectional view and (2) is a top view. The new method for preparing TEM proposed by the present invention can transfer specific materials through micro-regions, and the carbon film will not be damaged during the transfer process.

Claims

1. A PPC film for preparing TEM samples by dry method spot transfer, comprising a glass slide (1), a PDMS film (2), a transparent tape (3), a PPC film (4), and a transparent tape with a middle hole (5), characterized in that: The structure of the PPC film is as follows: a PDMS film (2) is fixed on a glass slide (1) by a transparent tape (3); a middle-hole transparent tape (5) with a PPC film (4) is adhered to the transparent tape (3); and the PPC film (4) is located at the opening of the middle-hole transparent tape; The glass slide (1) is a medical glass slide; The PDMS film (2) has a size of 0.3×0.3 cm and a thickness of 0.3 cm; The transparent tape (3) is a single-sided transparent tape; The PPC film (4) has a size of 1×1 cm and a thickness of 200 nm; The transparent tape (5) with a hole in the middle is a single-sided transparent tape, and the size of the hole is 0.5×0.5 cm.

2. A TEM sample preparation method based on the PPC film for preparing TEM samples by dry method spot transfer as claimed in claim 1, characterized in that The steps are as follows: Step 1: The PPC film adheres the sample material at a fixed point, and the sample material is prepared on the SiO2 substrate by mechanical peeling; the substrate with the sample material is placed on the base of the transfer platform; the target sample material is found under the microscope on the transfer platform; with the help of the transfer platform, the prepared PPC film is gently pressed on the sample material; the base of the sample stage is heated to 45°C to soften the PPC film and tightly absorb the sample material, and then cooled to room temperature; the slide glass is gently lifted by the mechanical arm, and the sample is adhered to the PPC film; this process can be repeated until the sample is adhered by the PPC film; Step 2: Transfer the sample to the copper mesh and place the PDMS film on the SiO2 substrate; place the copper mesh in the middle of the PDMS and place it on the base of the transfer platform; under the microscope of the transfer platform, use the robotic arm to gently press the PPC film with the sample material adhered to the carbon film of the copper mesh; heat the base of the transfer platform to 120°C to make the melted PPC film stick tightly to the carbon film; after 5 minutes, slowly lift the glass slide, and the sample material and the melted PPC film adhere to the copper mesh together; this process can be repeated until the sample material adheres to the copper mesh; Step 3: Dissolve the PPC film and complete the TEM sample preparation. Place the copper mesh with the sample material and the substrate in a glass container, add acetone and soak for 10 minutes. The PPC film and PDMS film will be dissolved, while the sample material will adhere to the copper mesh. After gently blowing dry with an air gun, the TEM sample preparation is completed.

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