A Bi-based 0.07 Sn 0.93 Fabrication method of S-type room temperature ultrawide spectrum self-driven photodetector

Abstract

A Bi-based 0.07 Sn 0.93 The fabrication method of S-type room-temperature ultrawide spectrum self-driven photodetector belongs to the field of semiconductor devices. 0.07 Sn 0.93 Methods for preparing S single crystals include: growing large-size Bi single crystals using chemical vapor transport methods. 0.07 Sn 0.93 S single crystal, 2D Bi obtained by mechanical exfoliation 0.07 Sn 0.93 Si nanosheets were then transferred to a SiO2 / Si substrate using dry transfer technology and a two-dimensional transfer platform. Two electrode patterns were etched, and a metal layer was deposited using a high-vacuum thermal evaporation deposition system to obtain 2D Bi nanosheets. 0.07 Sn 0.93 S nanosheet ultrawideband spectral self-driven photodetector. Based on 2D Bi 0.07 Sn 0.93 The S nanosheet photodetector exhibits a good ultrawide spectral response under room temperature and zero bias conditions.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor devices, specifically relating to a method based on Bi 0.07 Sn 0.93 A method for fabricating a room-temperature ultrawide spectrum self-driven photodetector. Background Technology

[0002] Ultrawideband self-driven photodetectors can process optical signals from different wavelengths simultaneously, enabling better target detection and identification. They have important applications in astronomy, biological diagnostics, land cover classification, and 3D surface reconstruction. Currently, ultrawideband self-driven photodetectors primarily utilize epitaxially grown semiconductors such as InP, HgCdTe, and II superlattices. However, these materials suffer from low yields, complex manufacturing processes, and high costs, limiting their applications. Therefore, exploring new ultrawideband light-absorbing materials has become an important objective.

[0003] Emerging two-dimensional layered semiconductor materials are gradually becoming ideal materials for constructing photodetectors due to their excellent photoelectric properties, atomic layer thickness, tunable band gap, and good compatibility with complementary metal-oxide-semiconductor (CMOS) processes. Materials such as bP, MoTe2, and GeSe have demonstrated great application potential in visible and near-infrared light detection. Compared to other two-dimensional layered semiconductor materials, SnS crystals, with their narrower band gap, have been shown to have better photoelectric properties in the near-infrared spectral range. However, to date, the band gap can only be controlled within a certain range by changing the number of layers and stress, making it difficult to simultaneously cover the ultraviolet, visible, and infrared spectra of SnS-based photodetectors. Substitution doping with elements such as V, Fe, Nb, and Ta can control the band structure, phonon vibrations, lattice symmetry, and carrier transport within a certain range. Therefore, developing room-temperature ultrawide spectral self-driven photodetectors using atomic substitution doping of SnS nanosheets is of great significance. Summary of the Invention

[0004] The purpose of this invention is to address the key technical problem that a single device cannot efficiently detect ultraviolet, visible, and near-infrared light at room temperature and zero bias voltage, and to provide a method based on Bi... 0.07 Sn 0.93 A method for fabricating a room-temperature ultrawide spectrum self-driven photodetector.

[0005] The objective of this invention is achieved through the following solution:

[0006] A Bi-based 0.07 Sn 0.93 The fabrication method of the S-type room-temperature ultrawide spectrum self-driven photodetector includes the following steps:

[0007] S1: Weigh a certain amount of Bi powder, Sn powder and S powder, wherein the mass ratio of Bi powder, Sn powder and S powder is 1:1:2. Weigh 10-20mg of iodine granules, mix them evenly and transfer them to an ampoule.

[0008] S2: Using high-vacuum sealing equipment, the vacuum level in the ampoule is reduced to below 4 × 10⁻⁶. -3 Pa, oxygen content less than 3ppm, and the rotation speed of the ampoule is maintained at 2-5r / min during the heat sealing process;

[0009] S3: Place the heat-sealed ampoule horizontally in a dual-temperature zone tube furnace and set the temperature of the dual-temperature zone tube furnace; obtain large-sized Bi with a metallic luster in the reaction zone. 0.07 Sn 0.93 S single crystal;

[0010] S4 employs PDMS dry transfer technology and a two-dimensional material transfer platform to transfer mechanically exfoliated 2D Bi 0.07 Sn 0.93 S nanosheets were transferred to a SiO2 / Si substrate;

[0011] S5: The electrode pattern is prepared through steps such as coating, pre-baking, exposure, development, fixing, and post-baking.

[0012] S6: Metal is deposited onto the photoresist surface using a thermal evaporation coating machine, and the metal film is peeled off using a lift-off process;

[0013] S7: Use an aluminum wire spot welder to weld the leads to complete the 2D Bi 0.07 Sn 0.93 Fabrication of S nanosheet ultrawide spectrum self-driven photodetector.

[0014] Furthermore, the Bi powder is of 5N grade with a particle size of 200 nm, the Sn powder is of 5N grade with a particle size of 200 nm, and the S powder is of 5N grade with a particle size of 100 nm. The purity of the Bi powder, Sn powder, and S powder is not less than 99.999%, and the purity of the iodine particles is required to be analytical grade.

[0015] Further, in step S3, the temperature settings of the dual-zone tube furnace are as follows: the reaction zone temperature is increased to 450°C at a rate of 2-4°C / min and held for 60 minutes, then increased to 720°C at a rate of 4-5°C / min and held for 4380 minutes. The growth zone temperature is increased to 450°C at a rate of 2-4°C / min and held for 60 minutes, then increased to 750°C at a rate of 4-5°C / min and held for 1440 minutes. Next, the growth zone is cooled to 520°C at a rate of 7-8°C / min and held for 2500-3000 minutes.

[0016] Furthermore, step S4 specifically includes:

[0017] S41: Adhere the PDMS polymer film onto the transparent glass sheet, ensuring a smooth surface free of bubbles.

[0018] S42: Use a mechanical peeling tool to peel off Bi from the PDMS polymer film. 0.07 Sn 0.93 S-single-crystal nanosheets.

[0019] S43: Flip the PDMS polymer film with nanosheets and suspend it on the glass slide of the two-dimensional material transfer platform.

[0020] S44: With the assistance of the microscopic imaging system, adjust the slide displacement platform to align the nanosheets on the PDMS polymer film with the SiO2 / Si substrate. Slowly lower the cantilever height to ensure full contact and pressure between the PDMS polymer film and the target substrate.

[0021] S45: Slowly raise the cantilever to achieve bonding of the nanosheet to the SiO2 / Si substrate.

[0022] S46: Repeat steps S41-S45 to obtain a first nanosheet layer of 100-150 nm on the SiO2 / Si substrate; continue to repeat steps S41-S45 to prepare a second nanosheet layer of 20-30 nm thickness on the surface of the first nanosheet layer to obtain the initial sample.

[0023] Furthermore, step S5 specifically includes:

[0024] S51: Applying adhesive

[0025] Place the initial sample on the suction cup of the spin coater and turn on the vacuum pump to hold the substrate. Use a dropper or an automatic dispensing device to drop an appropriate amount of photoresist into the center of the second nanosheet layer. First, rotate at a low speed of 500-700 r / min for 5-10 seconds to spread the photoresist evenly on the surface of the nanosheet layer. Then, rotate at a high speed of 3000-6000 r / min for 30-50 seconds to form a uniform thin film of photoresist.

[0026] S52: Pre-baking

[0027] Place the photoresist-coated substrate on a hot plate for pre-baking. Set the temperature to 100-120℃ and bake for 1-5 minutes to remove the solvent from the photoresist and allow it to cure.

[0028] S53: Exposure

[0029] The substrate with cured photoresist is placed in the photolithography machine, and the designed electrode pattern mask is aligned with the substrate. A mercury lamp is used as the light source, and the exposure time is 10-30 seconds, allowing the photoresist to undergo a photochemical reaction in the light-transmitting area of ​​the mask.

[0030] S54: Development

[0031] After exposure, immerse the substrate in the developer. The development time is 60-100 seconds.

[0032] S55: Fixing

[0033] Soak the sample in fixer for 10-50 minutes.

[0034] S56: Post-baking

[0035] The fixed sample is then post-baked at a temperature of 120-160℃ for 5-8 minutes to further solidify the photoresist pattern, enhance the adhesion between the photoresist and the substrate, and make the electrode pattern more stable.

[0036] Further, in step S6, the substrate with the photoresist pattern is placed into the chamber of the thermal evaporation coating instrument, the sample is fixed, and the chamber vacuum degree is 3×10⁻⁶. -4 -5×10 -4 Pa, first, an Au layer or an Ag layer is deposited on the surface of the photoresist, and then a Cr layer is deposited on the surface of the Au layer or Ag layer. The deposition rate of Au or Ag is: Cr deposition rate: The Au or Ag layer has a thickness of 40-50 nm, and the Cr layer has a thickness of 4-6 nm.

[0037] After coating is completed, the sample is removed from the coating machine and immersed in a solvent such as acetone or N-methylpyrrolidone. The photoresist dissolves under the action of the solvent, and the metal film on it peels off because it is no longer supported by the underlying photoresist. The metal under the photoresist-covered area remains on the substrate, thus forming the desired metal pattern. The sample is then rinsed with solvent to remove residual photoresist and metal fragments, and then dried.

[0038] The method of the present invention has the following advantages:

[0039] 1. This method uses iodine particles as a gas delivery medium, which can effectively reduce Bi 0.07 Sn 0.93 The activation energy of S enables the gas-phase reaction to occur at metal melting points below that of Bi, while inhibiting Sn+S→SnS and Bi+S→SnS.

[0040] 2. Compared to existing technologies, the growth zone temperature of 750℃ is higher than the reaction zone temperature of 720℃ before reaching the growth temperature of 520℃, allowing the source to fully volatilize and react. This significantly improves the efficiency of Bi. 0.07 Sn 0.93 The size and quality of the S single crystal, and the control of the photosensitive layer 2DBi of the contact source and drain electrodes through the S4 step. 0.07Sn 0.93 The thickness difference of the S nanosheets and the interface state lead to differences in the height of the Schottky barrier, forming an internal electric field, which enables the fabrication of an ultrawide spectrum self-driven photodetector.

[0041] 3. By introducing Bi into the SnS binary material, the band gap can be controlled. The mass ratio of Bi powder, Sn powder, and S powder was set to 1:1:2. The heating rate and temperature in the dual-temperature zone were also set. Bi powder prepared under these ratio and heating rate conditions... 0.07 Sn 0.93 S has a larger single crystal size.

[0042] 4. This application is based on 2D Bi 0.07 Sn 0.93 The S nanosheet photodetector exhibits a good ultrawide spectral response (265nm-1550nm) under room temperature and zero bias conditions. Attached Figure Description

[0043] Figure 1 Bi in this invention 0.07 Sn 0.93 Schematic diagram of the S single crystal growth process.

[0044] Figure 2 Bi in this invention 0.07 Sn 0.93 S single crystal growth temperature curve.

[0045] Figure 3 Bi in this invention 0.07 Sn 0.93 S-Crystal optical image.

[0046] Figure 4 2D Bi in this invention 0.07 Sn 0.93 Schematic diagram of an S-type photodetector.

[0047] Figure 5 2D Bi in this invention 0.07 Sn 0.93 Image of an S photodetector.

[0048] Figure 6 2D Bi in this invention 0.07 Sn 0.93 S-photodetector wavelength response spectrum.

[0049] Figure 7 2D Bi in this invention 0.07 Sn 0.93 Photocurrent spectrum of S photodetector under zero bias voltage.

[0050] Figure 82D Bi in this invention 0.07 Sn 0.93 The surface potential difference of the S photodetector device.

[0051] Figure 9 2D Bi in this invention 0.07 Sn 0.93 Diagram of the self-driven photodetector mechanism of the S photodetector. Detailed Implementation

[0052] The present invention will be further described below with reference to embodiments:

[0053] Example 1

[0054] A Bi-based 0.07 Sn 0.93 The fabrication method of the S-type room-temperature ultrawide spectrum self-driven photodetector includes the following steps:

[0055] S1: Weigh 0.1g Bi powder, 0.1g Sn powder and 0.2g S powder, then weigh 10mg iodine granules, mix them evenly and transfer them to an ampoule;

[0056] S2: Using high-vacuum sealing equipment, the vacuum inside the ampoule is 1×10⁻⁶. -3 Pa, oxygen content 1ppm, ampoule rotation speed maintained at 5r / min during heat sealing process;

[0057] S3: Place the heat-sealed ampoules horizontally in a dual-zone tube furnace. The temperature settings for the dual-zone tube furnace are as follows: The reaction zone temperature is increased to 450°C at a rate of 2°C / min and held for 60 minutes, then increased to 720°C at a rate of 4°C / min and held for 4380 minutes. The growth zone temperature is increased to 450°C at a rate of 2°C / min and held for 60 minutes, then increased to 750°C at a rate of 4.2°C / min and held for 1440 minutes. Next, the growth zone temperature is decreased to 520°C at a cooling rate of 7.7°C / min and held for 2880 minutes. Large-sized Bi particles with a metallic luster are obtained in the reaction zone. 0.07 Sn 0.93 S single crystal;

[0058] S4: Using PDMS dry transfer technology and a two-dimensional transfer platform, the mechanically stripped 2DBi 0.07 Sn 0.93 S nanosheets were transferred to a SiO2 / Si substrate;

[0059] S41: Adhere the PDMS polymer film onto the transparent glass sheet, ensuring a smooth surface free of bubbles.

[0060] S42: Use a mechanical peeling tool to peel off Bi from the PDMS polymer film. 0.07 Sn0.93 S-single-crystal nanosheets.

[0061] S43: Flip the PDMS polymer film with nanosheets and suspend it on the glass slide of the two-dimensional material transfer platform.

[0062] S44: With the assistance of the microscopic imaging system, adjust the slide displacement platform to align the nanosheets on the PDMS polymer film with the SiO2 / Si substrate. Slowly lower the cantilever height to ensure full contact and pressure between the PDMS polymer film and the target substrate.

[0063] S45: Slowly raise the cantilever to achieve bonding of the nanosheet to the SiO2 / Si substrate.

[0064] S46: Repeat steps S41-S45 to obtain a first nanosheet layer of 100 nm on the SiO2 / Si substrate; continue to repeat steps S41-S45 to prepare a second nanosheet layer of 20 nm thickness on the surface of the first nanosheet layer.

[0065] S5: The electrode pattern is prepared through steps such as coating, pre-baking, exposure, development, fixing, and post-baking.

[0066] S6: Metal is deposited onto the photoresist surface using a thermal evaporation coating machine, and the metal film is peeled off using a lift-off process;

[0067] The substrate with the photoresist pattern was placed into the chamber of the thermal evaporation coating apparatus, and the sample was fixed in place. The chamber vacuum level was 3 × 10⁻⁶. -4 Pa, first, an Au layer is deposited on the surface of the photoresist, and then a Cr layer is deposited on the surface of the Au layer. The Au deposition rate is: Cr deposition rate: The Au layer is 40 nm thick, and the Cr layer is 4 nm thick.

[0068] S7: Use an aluminum wire spot welder to weld the leads to complete the 2D Bi 0.07 Sn 0.93 Fabrication of S nanosheet ultrawide spectrum self-driven photodetector.

[0069] Example 2

[0070] A Bi-based 0.07 Sn 0.93 The fabrication method of the S-type room-temperature ultrawide spectrum self-driven photodetector includes the following steps:

[0071] S1: Weigh 0.1g Bi powder, 0.1g Sn powder and 0.2g S powder, then weigh 15mg iodine granules, mix them evenly and transfer them to an ampoule;

[0072] S2: Using high-vacuum sealing equipment, the vacuum inside the ampoule is 3×10⁻⁶. -3 Pa, oxygen content is 2ppm, and the ampoule is kept rotating at 3r / min during the heat sealing process;

[0073] S3: Place the heat-sealed ampoules horizontally in a dual-zone tube furnace. The temperature settings for the dual-zone tube furnace are as follows: The reaction zone temperature is increased to 450°C at a rate of 3°C / min and held for 60 minutes, then increased to 720°C at a rate of 4.5°C / min and held for 4380 minutes. The growth zone temperature is increased to 450°C at a rate of 3°C / min and held for 60 minutes, then increased to 750°C at a rate of 4.5°C / min and held for 1440 minutes. Next, the growth zone temperature is decreased to 520°C at a rate of 7°C / min and held for 2880 minutes. Large-sized Bi particles with a metallic luster are obtained in the reaction zone. 0.07 Sn 0.93 S single crystal;

[0074] S4: Using PDMS dry transfer technology and a two-dimensional transfer platform, the mechanically stripped 2DBi 0.07 Sn 0.93 S nanosheets were transferred to a SiO2 / Si substrate;

[0075] S41: Adhere the PDMS polymer film onto the transparent glass sheet, ensuring a smooth surface free of bubbles.

[0076] S42: Use a mechanical peeling tool to peel off Bi from the PDMS polymer film. 0.07 Sn 0.93 S-single-crystal nanosheets.

[0077] S43: Flip the PDMS polymer film with nanosheets and suspend it on the glass slide of the two-dimensional material transfer platform.

[0078] S44: With the assistance of the microscopic imaging system, adjust the slide displacement platform to align the nanosheets on the PDMS polymer film with the SiO2 / Si substrate. Slowly lower the cantilever height to ensure full contact and pressure between the PDMS polymer film and the target substrate.

[0079] S45: Slowly raise the cantilever to achieve bonding of the nanosheet to the SiO2 / Si substrate.

[0080] S46: Repeat steps S41-S45 to obtain a first nanosheet layer of 120 nm on the SiO2 / Si substrate; continue to repeat steps S41-S45 to prepare a second nanosheet layer of 25 nm thickness on the surface of the first nanosheet layer.

[0081] S5: The electrode pattern is prepared through steps such as coating, pre-baking, exposure, development, fixing, and post-baking.

[0082] S6: Metal is deposited onto the photoresist surface using a thermal evaporation coating machine, and the metal film is peeled off using a lift-off process;

[0083] The substrate with the photoresist pattern was placed into the chamber of the thermal evaporation coating apparatus, and the sample was fixed in place. The chamber vacuum level was 4 × 10⁻⁶. -4 Pa, first, an Au layer is deposited on the surface of the photoresist, and then a Cr layer is deposited on the surface of the Au layer. The Au deposition rate is: Cr deposition rate: The Au layer is 45 nm thick, and the Cr layer is 5 nm thick.

[0084] S7: Use an aluminum wire spot welder to weld the leads to complete the 2D Bi 0.07 Sn 0.93 Fabrication of S nanosheet ultrawide spectrum self-driven photodetector.

[0085] Example 3

[0086] A Bi-based 0.07 Sn 0.93 The fabrication method of the S-type room-temperature ultrawide spectrum self-driven photodetector includes the following steps:

[0087] S1: Weigh 0.1g Bi powder, 0.1g Sn powder and 0.2g S powder, then weigh 20mg iodine granules, mix them evenly and transfer them to an ampoule;

[0088] S2: Using high-vacuum sealing equipment, the vacuum level in the ampoule is 2×10⁻⁶. -3 Pa, oxygen content 1ppm, ampoule rotation speed maintained at 2r / min during heat sealing process;

[0089] S3: Place the heat-sealed ampoules horizontally in a dual-zone tube furnace. The temperature settings for the dual-zone tube furnace are as follows: The reaction zone temperature is increased to 450°C at a rate of 4°C / min and held for 60 minutes, then increased to 720°C at a rate of 5°C / min and held for 4380 minutes. The growth zone temperature is increased to 450°C at a rate of 4°C / min and held for 60 minutes, then increased to 750°C at a rate of 4.8°C / min and held for 1440 minutes. Next, the growth zone temperature is decreased to 520°C at a rate of 8°C / min and held for 3000 minutes. Large-sized Bi particles with a metallic luster are obtained in the reaction zone. 0.07 Sn 0.93 S single crystal;

[0090] S4: Using PDMS dry transfer technology and a two-dimensional transfer platform, the mechanically stripped 2DBi 0.07 Sn 0.93 S nanosheets were transferred to a SiO2 / Si substrate;

[0091] S41: Adhere the PDMS polymer film onto the transparent glass sheet, ensuring a smooth surface free of bubbles.

[0092] S42: Use a mechanical peeling tool to peel off Bi from the PDMS polymer film. 0.07 Sn 0.93 S-single-crystal nanosheets.

[0093] S43: Flip the PDMS polymer film with nanosheets and suspend it on the glass slide of the two-dimensional material transfer platform.

[0094] S44: With the assistance of the microscopic imaging system, adjust the slide displacement platform to align the nanosheets on the PDMS polymer film with the SiO2 / Si substrate. Slowly lower the cantilever height to ensure full contact and pressure between the PDMS polymer film and the target substrate.

[0095] S45: Slowly raise the cantilever to achieve bonding of the nanosheet to the SiO2 / Si substrate.

[0096] S46: Repeat steps S41-S45 to obtain a first nanosheet layer of 150 nm on the SiO2 / Si substrate; continue to repeat steps S41-S45 to prepare a second nanosheet layer of 30 nm thickness on the surface of the first nanosheet layer.

[0097] S5: The electrode pattern is prepared through steps such as coating, pre-baking, exposure, development, fixing, and post-baking.

[0098] S6: Metal is deposited onto the photoresist surface using a thermal evaporation coating machine, and the metal film is peeled off using a lift-off process;

[0099] The substrate with the photoresist pattern was placed into the chamber of the thermal evaporation coating apparatus, and the sample was secured. The chamber vacuum level was 5 × 10⁻⁶. -4 Pa, first, an Ag layer is deposited on the surface of the photoresist, and then a Cr layer is deposited on the surface of the Ag layer. The Ag deposition rate is as follows: Cr deposition rate: The Ag layer is 50 nm thick, and the Cr layer is 6 nm thick.

[0100] S7: Use an aluminum wire spot welder to weld the leads to complete the 2D Bi 0.07 Sn 0.93 Fabrication of S nanosheet ultrawide spectrum self-driven photodetector.

Claims

1. A Bi 0.07 Sn 0.93 S-based room-temperature ultra-wide spectrum self-driven photodetector, characterized in that, Comprising the following steps: S1: weigh a certain amount of Bi powder, Sn powder and S powder, wherein the mass ratio of Bi powder, Sn powder and S powder is 1:1:2, and then weigh 10-20 mg of iodine particles, mix them uniformly and then transfer them to an ampoule; S2: using high vacuum sealing equipment, the ampoule bottle vacuum degree is lower than 4x10 -3 Pa, oxygen content is lower than 3ppm, the ampoule bottle keeps rotating speed of 2-5r / min during heat sealing process; S3: Place the ampoule sealed by hot melting on the double-temperature zone tube furnace, set the temperature of the double-temperature zone tube furnace; obtain large-size Bi 0.07 Sn 0.93 S single crystal; S4: PDMS dry transfer technique and two-dimensional material transfer platform are used to transfer mechanically exfoliated 2D Bi 0.07 Sn 0.93 nanosheets to SiO2 / Si substrate; S5: complete the preparation of the electrode pattern through the steps of gluing, pre-baking, exposure, development, fixation, post-baking, etc.; S6: evaporate the metal onto the surface of the photoresist by a thermal evaporation coating instrument, and strip the metal film by a Lift-off process; S7: Wire bonding with aluminum wire bonding machine, complete 2DBi 0.07 Sn 0.93 Preparation of S nanosheet ultra-wide spectrum self-driven photodetector device.

2. The method for fabricating a self-driven photodetector as described in claim 1, characterized in that, The Bi powder is 5N grade, the particle size is 200 nm, the Sn powder is 5N grade, the particle size is 200 nm, the S powder is 5N grade, the particle size is 100 nm, and the purity of the iodine particles is required to be analytical pure.

3. The method for fabricating a self-driven photodetector as described in claim 2, characterized in that, In step S3, the temperature of the double-temperature-zone tube furnace is set as follows: the temperature of the reaction zone is increased to 450 DEG C at a rate of 2-4 DEG C / min and maintained for 60 min, and then increased to 720 DEG C at a rate of 4-5 DEG C / min and maintained for 4380 min; the temperature of the growth zone is increased to 450 DEG C at a rate of 2-4 DEG C / min and maintained for 60 min, and then increased to 750 DEG C at a rate of 4.2 DEG C / min and maintained for 1440 min, and then the growth zone is cooled to 520 DEG C at a rate of 7-8 DEG C / min and maintained for 2500-3000 min.

4. The method for fabricating a self-driven photodetector as described in claim 3, characterized in that, Step S4 is specifically: S41: adhere the PDMS high molecular film to the transparent glass sheet to ensure that the surface is flat and bubble-free; S42: using a mechanical peeling tool to peel off Bi from the PDMS high molecular film 0.07 Sn 0.93 S single-crystal nanosheet S43: turn over the PDMS high molecular film with nanosheets and suspend and fix it to the glass slide of the two-dimensional material transfer platform; S44: under the assistance of a microscopic imaging system, adjust the glass slide displacement platform to align the nanosheets on the PDMS high molecular film with the SiO2 / Si substrate, slowly lower the cantilever height, and make the PDMS high molecular film fully contact and press the target substrate; S45: slowly lift the cantilever to realize the adhesion of the nanosheets to the target substrate; S46: repeat steps S41-S45 to obtain a first layer of nanosheet layer with a thickness of 100-150 nm on the SiO2 / Si substrate; continue to repeat steps S41-S45 to prepare a second layer of nanosheet layer with a thickness of 20-30 nm on the surface of the first layer of nanosheet layer.

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