A method for peeling thin-layered materials suitable for scanning tunneling microscopy

Abstract

This invention specifically discloses a method for peeling off thin-layered materials suitable for scanning tunneling microscopy, comprising the following steps: placing a layered material single crystal block between two PDMS films, pressing them firmly together, and then peeling off one layer of PDMS film to obtain a layered material single crystal block / PDMS film; applying high-vacuum conductive adhesive to the surface of a substrate, and then pressing the surface of the obtained layered material single crystal block / PDMS film firmly together with the substrate to obtain a PDMS film / layered material single crystal block / high-vacuum conductive adhesive / substrate; heating the PDMS film / layered material single crystal block / high-vacuum conductive adhesive / substrate to cure the conductive adhesive, and after heating, peeling off the PDMS film to obtain a layered material single crystal block / high-vacuum conductive adhesive / substrate; applying adhesive tape to the outer surface of the layered material single crystal block / high-vacuum conductive adhesive / substrate, and then quickly peeling off the tape, repeating this process until the layered material is light blue or nearly transparent.

Description

Technical Field

[0001] This invention pertains to novel material processing and preparation technologies, specifically relating to a method for peeling off thin-layered materials suitable for scanning tunneling microscopy analysis. Background Technology

[0002] Since the discovery of graphene in 2004, a wide variety of two-dimensional layered materials have been explored and pursued by researchers, including boron nitride, black phosphorus, transition metal chalcogenides, and borenes. The unique optoelectronic properties exhibited by these layered materials have given them strong vitality in the semiconductor industry. In recent years, novel layered materials with magnetic, ferroelectric, and multiferroic properties have also been verified theoretically or experimentally. These materials exhibit properties different from traditional ferromagnetic and ferroelectric materials. Their emergence has not only enriched the family of layered materials but also provided a solid foundation for researchers to construct novel functional devices.

[0003] To achieve the rational application of materials, it is essential to understand their fundamental properties, intrinsic material interaction processes, and physical principles. Scanning tunneling microscopy (STM) is a powerful tool for studying material surfaces and interfaces, enabling the observation and analysis of material properties at the atomic scale. Although researchers have gained some understanding of layered materials, the physical properties of some novel layered materials, including CuInP2S6, CrI3, and VSe2, still lack atomic-scale discovery and exploration. Often, the superior properties of these layered materials are only apparent in single-layer or few-layer cases. Effective exfoliation of layered materials is the first step in their research and application. Currently, common methods for exfoliating layered materials include mechanical exfoliation, ultrasonic centrifugation, and grinding. However, these methods all have limitations, such as small area, low efficiency, low yield, high power consumption, and limited application range, restricting their research in the field of scanning tunneling microscopy.

[0004] Therefore, it is necessary to develop a new exfoliation method to solve the problem that traditional mechanical exfoliation is difficult to apply to the field of scanning tunneling microscopy, thereby facilitating the microscopic exploration of the properties of novel materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for peeling off thin layered materials suitable for scanning tunneling microscopy.

[0006] To achieve the above objectives, one of the technical solutions of the present invention is: a method for peeling off thin-layered materials suitable for scanning tunneling microscopy, comprising the following steps:

[0007] (1) Take the target layered material single crystal block and place it between two PDMS films. After pressing it firmly, peel off one PDMS film to obtain the layered material single crystal block / PDMS film.

[0008] (2) Apply high vacuum conductive adhesive to the required substrate surface, then press the outer surface of the layered material single crystal block / PDMS film obtained in step (1) onto the substrate and press it firmly to obtain PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate.

[0009] (3) Heat the PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate obtained in step (2) to cure the conductive adhesive. After heating, peel off the PDMS film to obtain the layered material single crystal block / high vacuum conductive adhesive / substrate.

[0010] (4) Apply adhesive tape to the outer surface of the layered material single crystal block / high vacuum conductive adhesive / substrate obtained in step (3), and then quickly tear off the tape. Repeat this process several times until the thickness of the obtained layered material single crystal block reaches the expected requirement, and obtain a few layers of layered material single crystal / high vacuum conductive adhesive / substrate; the expected requirement is that the layered material is observed to be light blue or nearly transparent under a metallographic microscope.

[0011] In a preferred embodiment of the present invention, the material of the target layered material single crystal block in step (1) includes one of highly oriented pyrolytic graphene (HOPG), boron nitride, black phosphorus, transition metal chalcogenides, and other novel layered materials. The transition metal chalcogenides include MoS2, MoSe2, WS2, and WSe2, etc., and the other novel layered materials include CuInP2S6, CrI3, and VSe2, etc.

[0012] In a preferred embodiment of the present invention, the PDMS film in step (1) is a high molecular polymer polydimethylsiloxane with a thickness of 300-500 μm and a size slightly larger than the substrate.

[0013] In a preferred embodiment of the present invention, the high vacuum conductive adhesive in step (2) includes one of high vacuum conductive silver adhesive, high vacuum graphite conductive adhesive, etc.

[0014] In a preferred embodiment of the present invention, the amount of high vacuum conductive adhesive used in step (2) is such that after being pressed and adhered firmly, the high vacuum conductive adhesive just covers the size of the single crystal of the target layered material.

[0015] In a preferred embodiment of the present invention, the substrate in step (2) includes one of the following common hard materials: gold, silver, copper, etc., metal single crystals or alloys, Si wafers, SiO2 / Si wafers, tantalum wafers, sapphire, GaN, etc.

[0016] In a preferred embodiment of the present invention, the heating temperature in step (3) should not exceed 120°C, preferably 80-100°C, and the heating time is 2-3 hours.

[0017] In a preferred embodiment of the present invention, the adhesive tape in step (4) includes one of the following: polyimide tape, transparent PE protective film, Nitto tape, electronic grade tape (hereinafter referred to as blue film tape).

[0018] To achieve the above objectives, the second technical solution of the present invention is: a few-layered material single crystal / high vacuum conductive adhesive / substrate obtained by the above-mentioned peeling method.

[0019] In a preferred embodiment of the present invention, the few-layered material single crystal / high vacuum conductive adhesive / substrate comprises, from the outside to the inside, a few-layered material single crystal, a high vacuum conductive adhesive, and a substrate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention utilizes the fixing effect of high-vacuum conductive adhesive to fix layered materials onto a specified substrate; on the other hand, it utilizes its conductive properties to make it compatible with the field of scanning tunneling microscopy.

[0022] 2. Unlike the traditional method of peeling off adhesive tape, this invention uses a method similar to peeling off a single crystal. By repeatedly separating the other end of the single crystal of the thick layered material after fixing one end, the single crystal of the layered material is thinned to the expected thickness.

[0023] 3. The present invention has simple operation steps and can efficiently and conveniently obtain high-quality, large-area, and few-layer layered material crystals; it broadens the ability of scanning tunneling microscopy to explore layered materials, especially novel multiferroic layered materials, and provides effective technical support for discovering the physical properties of such novel two-dimensional materials and revealing their intrinsic microscopic mechanisms. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 This is a flowchart of the steps of a thin-layered material peeling method suitable for scanning tunneling microscopy analysis according to the present invention;

[0026] Figure 2 This is a schematic diagram of the sample structure obtained by the stripping method of the present invention;

[0027] Figure 3 The image shows an optical micrograph of WS2 after the peeling process in Example 1.

[0028] Figure 4This is a WS2 scanning tunneling microscope image of the morphology after the peeling was completed in Example 1;

[0029] Figure 5 This is an atomic resolution image obtained by WS2 scanning tunneling microscope after the stripping process in Example 1.

[0030] Figure 6 This is an optical micrograph of CuInP2S6 after the peeling process in Example 2. Detailed Implementation

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0032] Figure 1 This is a flowchart illustrating the operational steps of the present invention. The present invention provides a method for peeling off thin-layered materials suitable for scanning tunneling microscopy analysis, comprising the following steps:

[0033] (1) Take the target layered material single crystal block and place it between two PDMS films. After pressing it firmly, peel off one PDMS film to obtain the layered material single crystal block / PDMS film.

[0034] (2) Apply high vacuum conductive adhesive to the required substrate surface, then press the outer surface of the layered material single crystal block / PDMS film obtained in step (1) onto the substrate and press it firmly to obtain PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate.

[0035] (3) Heat the PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate obtained in step (2) to cure the conductive adhesive. After heating, peel off the PDMS film to obtain the layered material single crystal block / high vacuum conductive adhesive / substrate.

[0036] (4) Apply adhesive tape to the outer surface of the layered single crystal block / high vacuum conductive adhesive / substrate obtained in step (3), then quickly peel off the tape. Repeat this process several times until the thickness of the obtained layered single crystal block reaches the expected requirement, resulting in a few-layer layered single crystal / high vacuum conductive adhesive / substrate, the structural schematic diagram of which is shown below. Figure 2 As shown. The expected requirement is that the layered material appears light blue or nearly transparent when observed under a metallographic microscope.

[0037] In step (1), the target layered material single crystal bulk includes one of highly oriented pyrolytic graphene (HOPG), boron nitride, black phosphorus, transition metal chalcogenides, and other novel layered materials. The transition metal chalcogenides include MoS2, MoSe2, WS2, and WSe2, and the other novel layered materials include CuInP2S6, CrI3, and VSe2.

[0038] In step (1), the PDMS film is a high molecular polymer polydimethylsiloxane with a thickness of 300-500 μm and a size slightly larger than the substrate.

[0039] The high vacuum conductive adhesive in step (2) includes one of the following: high vacuum conductive silver adhesive, high vacuum graphite conductive adhesive, etc.

[0040] The amount of high vacuum conductive adhesive used in step (2) should not be too much. After pressing and adhering, the high vacuum conductive adhesive should just cover the size of the single crystal of the target layered material.

[0041] The substrate in step (2) includes one of the following common hard materials: single crystals or alloys of metals such as gold, silver, and copper, Si wafers, SiO2 / Si wafers, tantalum wafers, sapphire, and GaN.

[0042] The heating temperature in step (3) should not exceed 120°C, preferably 80-100°C, and the heating time should be 2-3 hours.

[0043] The adhesive tape in step (4) includes one of the following: polyimide tape, transparent PE protective film, Nitto tape, electronic grade tape (hereinafter referred to as blue film tape).

[0044] A few-layered material single crystal / high vacuum conductive adhesive / substrate obtained by the above-mentioned peeling method.

[0045] The few-layered material single crystal / high-vacuum conductive adhesive / substrate comprises, from the outside to the inside, a few-layered material single crystal, a high-vacuum conductive adhesive, and a substrate.

[0046] The raw materials involved in this invention, including layered material crystals, PDMS films, adhesive tapes, glass slides, cotton swabs, etc., can all be obtained from online shopping platforms. The adhesiveness of the PDMS film involved in this invention is not specifically required; it can be purchased from online shopping platforms or prepared independently. The method of adhering the film or tape to the layered material crystals involved in this invention is not particularly required and is consistent with common methods in the art.

[0047] The tape removal process involved in this invention must be rapid in order to improve the efficiency and effect of single crystal thinning.

[0048] Example 1

[0049] A method for thin-layer WS2 stripping suitable for scanning tunneling microscopy analysis comprises the following steps:

[0050] (1) Cut two PDMS films of about 7mm×7mm in size. Take one of them and stick it on the glass slide. Then take a 4mm×3mm WS2 single crystal block and place it on the glass slide. Then use another PDMS film to stick to the outer surface of the WS2 single crystal block. Then press gently with a soft cotton swab and quickly peel off the upper PDMS film to obtain a PDMS film with WS2 crystals.

[0051] (2) Take an appropriate amount of high vacuum conductive silver paste and apply it to the surface of a clean brass substrate. Then, attach the PDMS film with WS2 crystal obtained in step (1) to the conductive paste, so that the WS2 crystal is in contact with the conductive paste. Press it gently with a soft cotton swab so that the conductive paste spreads evenly and the size of the spread is basically consistent with the area of ​​the WS2 crystal. This will give you a PDMS film / WS2 crystal block / conductive silver paste / brass substrate.

[0052] (3) Place the PDMS film / WS2 crystal block / conductive silver paste / brass substrate obtained in step (2) on a heating platform and heat it uniformly at 80°C for 3 hours. Then peel off the PDMS film to obtain WS2 crystal block / conductive silver paste / brass substrate.

[0053] (4) Cut a 2x4cm piece of blue film tape and stick it to the crystal surface of the WS2 crystal block / conductive silver paste / brass substrate obtained in step (3). Press it gently with a soft cotton swab and then quickly peel off the tape. Repeat this process 50 times until the WS2 crystal is not visible to the naked eye and a large area of ​​light blue or nearly transparent crystal appears under an optical microscope.

[0054] Figure 3 The optical micrographs of the WS2 crystals after the stripping process show that WS2 of different thicknesses has been successfully stripped, with local areas exceeding 100 nanometers in size, and large areas of thin layers exhibiting a light blue or transparent contrast. Figure 4 and Figure 5 The images show the morphology and atomic resolution of the WS2 crystal after exfoliation, as imaged using a scanning tunneling microscope. It can be observed that the WS2 surface is smooth with few defects, and its lattice period is 3.28 Å.

[0055] Example 2

[0056] A method for peeling thin CuInP2S6 layers suitable for scanning tunneling microscopy analysis, comprising the following steps:

[0057] (1) Cut two PDMS films of about 7mm×7mm in size. Take one of them and stick it on the glass slide. Then take a CuInP2S6 single crystal block of about 3mm×2mm in size and place it on the glass slide. Then use another PDMS film to stick to the surface of the CuInP2S6 single crystal. Then press it gently with a soft cotton swab and then quickly peel off the upper PDMS film to obtain a PDMS film with CuInP2S6 crystal.

[0058] (2) Take an appropriate amount of high vacuum conductive silver paste and apply it to the surface of a clean brass substrate. Then, attach the PDMS film with CuInP2S6 crystal obtained in step (1) to the conductive paste, so that the CuInP2S6 crystal is in contact with the conductive paste. Press it gently with a soft cotton swab so that the conductive paste spreads evenly and the size of the spread is basically the same as the area of ​​the CuInP2S6 crystal. This will give you a PDMS film / CuInP2S6 crystal block / conductive silver paste / brass substrate.

[0059] (3) Place the PDMS film / CuInP2S6 crystal bulk / conductive silver paste / brass substrate obtained in step (2) on a heating platform and heat it uniformly at 80°C for 3 hours. Then peel off the PDMS film to obtain CuInP2S6 crystal bulk / conductive silver paste / brass substrate.

[0060] (4) Cut an appropriate 2x4cm piece of blue film tape and stick it to the crystal surface of the CuInP2S6 crystal block / conductive silver paste / brass substrate obtained in step (3). Press it gently with a soft cotton swab and then quickly peel off the tape. Repeat this process until the CuInP2S6 crystal no longer shows a large area of ​​yellow with the naked eye and a large area of ​​light blue or nearly transparent crystal appears under an optical microscope.

[0061] Figure 6 The image shows an optical microscope image of the CuInP2S6 crystal after the stripping process. It can be seen that CuInP2S6 of different thicknesses has been successfully stripped, and large areas of flat sample appear on the surface. There are also large areas of thin layers that show light blue or transparent contrast.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for peeling off thin-layered materials suitable for scanning tunneling microscopy, characterized in that, Includes the following steps: (1) Take the target layered material single crystal block and place it between two PDMS films. After pressing it firmly, peel off one PDMS film to obtain the layered material single crystal block / PDMS film. (2) Apply high vacuum conductive adhesive to the required substrate surface, and then press the outer surface of the layered material single crystal block / PDMS film obtained in step (1) onto the substrate to obtain PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate. (3) Heat the PDMS film / layered material single crystal block / high vacuum conductive adhesive / substrate obtained in step (2) to cure the conductive adhesive. After heating, peel off the PDMS film to obtain the layered material single crystal block / high vacuum conductive adhesive / substrate. (4) Take an adhesive tape and attach it to the outer surface of the layered material single crystal block / high vacuum conductive adhesive / substrate obtained in step (3), and then quickly tear off the tape. Repeat this process until the layered material is observed to be light blue or nearly transparent under a metallographic microscope, and a few layers of layered material / high vacuum conductive adhesive / substrate are obtained.

2. The method as described in claim 1, characterized in that, The material of the target layered material single crystal bulk in step (1) includes one of highly oriented pyrolytic graphene, boron nitride, black phosphorus, transition metal chalcogenides, and other novel layered materials. The transition metal chalcogenides include MoS2, MoSe2, WS2, and WSe2, and the other novel layered materials include CuInP2S6, CrI3, and VSe2.

3. The method as described in claim 1, characterized in that, In step (1), the PDMS film is a high molecular polymer polydimethylsiloxane with a thickness of 300-500 μm.

4. The method as described in claim 1, characterized in that, The high vacuum conductive adhesive in step (2) includes one of high vacuum conductive silver adhesive and high vacuum graphite conductive adhesive.

5. The method as described in claim 1, characterized in that, The amount of high vacuum conductive adhesive used in step (2) is just enough to cover the outer surface of the layered material single crystal block after pressing and adhering.

6. The method as described in claim 1, characterized in that, The substrate in step (2) includes one of the following: single crystal gold, silver, copper or alloy, Si wafer, SiO2 / Si wafer, tantalum wafer, sapphire, and GaN.

7. The method as described in claim 1, characterized in that, The heating temperature in step (3) is 80-100℃, and the heating time is 2-3 hours.

8. The method as described in claim 1, characterized in that, The adhesive tape in step (4) includes one of the following: polyimide tape, transparent PE protective film, Nitto tape, and electronic grade tape.

9. A single-crystal / high-vacuum conductive adhesive substrate of a few-layered material obtained by peeling off the substrate as described in any one of claims 1-8.

10. The few-layered single-crystal / high-vacuum conductive adhesive / substrate as described in claim 9, characterized in that, From the outside in, it consists of a few layers of layered material single crystal, high-vacuum conductive adhesive, and substrate.

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