A method for preparing a van der waals metal thin film

Abstract

This invention discloses a method for preparing van der Waals metal thin films. The method includes the following steps: S1, coating a polyvinyl alcohol (PVA) film onto the surface of a supporting substrate; S2, depositing a metal film on the surface of the PVA film to obtain an intermediate; S3, placing the intermediate in water at 60-80°C to remove the PVA film, obtaining a floating metal film; transferring the metal film to the surface of a target substrate, and bonding the two together using van der Waals forces to obtain the final product. This invention utilizes the controllable dissolution properties of PVA, achieving the separation and transfer of the metal film from the supporting substrate using deionized water, avoiding the use of toxic chemical solvents and interface damage caused by high-energy bombardment. The method is simple, environmentally friendly, and can be widely applied to the preparation of van der Waals heterostructures such as metal-semiconductor and metal-insulator structures.

Description

Technical Field

[0001] This invention relates to the field of electronic materials and semiconductor device technology, and in particular to a method for preparing van der Waals metal thin films. Background Technology

[0002] In photodetectors, power devices, and related semiconductor electronic devices, the quality of metal-semiconductor and metal-insulator contacts directly affects the device's conductivity, rectification, and performance. Taking photodetectors as an example, they often employ gold-semiconductor contacts to construct Schottky junction structures. Traditional metal deposition processes (including high-energy methods such as thermal evaporation, electron beam evaporation, and sputtering deposition) easily introduce a large number of high-energy particle bombardment effects during deposition, causing defects, chemical bond disorder, and metal atom diffusion at the metal-semiconductor interface. This leads to Fermi level pinning and deviations of the Schottky barrier from theoretical values, limiting the optimization and tunability of device performance. Furthermore, interface defects and metal diffusion can form carrier recombination centers and leakage channels, resulting in weakened photoresponse, reduced response speed, and increased reverse leakage current, severely affecting device stability and lifespan.

[0003] To address the aforementioned issues, van der Waals metal integration technology has been developed in recent years. This technology avoids high-energy bombardment by physically stacking pre-fabricated metal films on semiconductor substrates, thus constructing a non-destructive, atomically flat metal-semiconductor interface. However, existing van der Waals metal transfer methods still have shortcomings: (1) most processes require the use of organic solvents or highly corrosive chemical reagents, resulting in poor environmental friendliness; (2) they affect the flatness and electrical properties of the film surface; (3) the process conditions are harsh, such as requiring high temperature, high pressure, or complex vacuum environments; and (4) the mechanical stress applied during the transfer process is difficult to control, often leading to micro-damage to the film.

[0004] Therefore, it is necessary to develop a non-destructive, environmentally friendly, and simple method for preparing van der Waals metal thin films. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present invention proposes a method for preparing van der Waals metal thin films, which has the characteristics of simple process, no interface damage, good uniformity and green environmental protection.

[0006] According to a first aspect of the present invention, a method for preparing a van der Waals metal thin film is provided, comprising the following steps: S1. Coat the surface of the support substrate with a polyvinyl alcohol film; S2. A metal film is deposited on the surface of the polyvinyl alcohol film to obtain an intermediate; S3. Place the intermediate in water at 60~80℃ to remove the polyvinyl alcohol film to obtain a floating metal film; transfer the metal film to the surface of the target substrate and bond the two together by van der Waals forces to obtain the final product.

[0007] According to a preferred embodiment of the present invention, the thickness of the polyvinyl alcohol film is 100~300 nm.

[0008] According to a preferred embodiment of the present invention, the thickness of the polyvinyl alcohol film is 200~250 nm.

[0009] According to a preferred embodiment of the present invention, the number average molecular weight of polyvinyl alcohol in the polyvinyl alcohol film is 70,000 to 130,000 g / mol.

[0010] According to a preferred embodiment of the present invention, in step S2, the thickness of the metal thin film is 10~500nm.

[0011] According to a preferred embodiment of the present invention, the metal in the metal film includes at least one of gold, aluminum, copper or silver.

[0012] According to a preferred embodiment of the present invention, in S1, the coating method includes spin coating; and / or, the spin coating rotation speed is 2000~4000 rpm.

[0013] According to a preferred embodiment of the present invention, the spin coating time is 30 to 60 seconds.

[0014] According to a preferred embodiment of the present invention, the supporting substrate includes at least one of a quartz sheet, a glass sheet, a silicon sheet, or a silicon dioxide substrate.

[0015] According to a preferred embodiment of the present invention, the target substrate includes at least one of a quartz sheet, a glass sheet, or a semiconductor substrate.

[0016] The preparation method according to embodiments of the present invention has at least the following beneficial effects: This invention provides a method for preparing van der Waals metal thin films based on polyvinyl alcohol (PVA) films as sacrificial layers, enabling the construction of low-damage, environmentally friendly metal-semiconductor interfaces. Compared to existing technologies, this method utilizes the controllable dissolution properties of PVA to achieve the separation and transfer of the metal thin film from the supporting substrate using deionized water, avoiding the use of toxic chemical solvents and interface damage caused by high-energy bombardment. The method is simple, environmentally friendly, and can be widely applied to the preparation of van der Waals heterostructures such as metal-semiconductor and metal-insulator structures.

[0017] (1) Green and environmentally friendly, simple process: The sacrificial layer can be dissolved by deionized water. The whole process does not require toxic chemical reagents or harsh operating conditions, which significantly reduces manufacturing costs and safety risks.

[0018] (2) No interface damage: The transfer process is free from high-energy particle bombardment, reducing interface defects and chemical bond disorder, and optimizing the interface state density.

[0019] (3) Uniform film thickness and controllable size: The metal thin film prepared by high vacuum thermal evaporation maintains its original thickness and uniformity after transfer, which meets the requirements of precise electrode design.

[0020] (4) Wide material compatibility: It can realize the transfer of various metal thin films such as aluminum (Al), silver (Ag), gold (Au), and copper (Cu), and is suitable for different electronic devices and optoelectronic devices.

[0021] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of the method of the present invention; Figure 2 This is a photograph of the gold film floating on the surface of deionized water during the transfer process in Example 1; Figure 3 This is a SEM comparison image of the gold film before and after the transfer of the polyvinyl alcohol film in Example 1; Figure 4 This is a photograph of the silver film floating on the surface of deionized water during the transfer process in Example 2; Figure 5 AFM image of gold film transferred from polyvinyl alcohol film; Figure 6 This is a comparison chart of light transmittance and resistivity of gold films transferred directly by vapor deposition and with polyvinyl alcohol film assistance, as shown in Example 3. Detailed Implementation

[0023] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0024] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0025] In some embodiments of the present invention, a method for preparing van der Waals metal thin films is provided, comprising the following steps: S1. Coat the surface of the support substrate with a polyvinyl alcohol film; S2. A metal film is deposited on the surface of the polyvinyl alcohol film to obtain an intermediate; S3. Place the intermediate in water at 60~80℃ to remove the polyvinyl alcohol film to obtain a floating metal film; transfer the metal film to the surface of the target substrate and bond the two together by van der Waals forces to obtain the final product.

[0026] The structural schematic diagram of the present invention is shown below. Figure 1 As shown, it includes a support substrate (100), a polyvinyl alcohol film (200), a metal film (300), and a target substrate (400).

[0027] It is understood that this invention provides a method for preparing van der Waals metal thin films based on polyvinyl alcohol (PVA) films as sacrificial layers, thereby achieving low-damage, environmentally friendly metal-semiconductor interface construction. Compared to existing technologies, this method utilizes the controllable dissolution properties of PVA to achieve the separation and transfer of the metal thin film from the supporting substrate using deionized water, avoiding the use of toxic chemical solvents and interface damage caused by high-energy bombardment. The method is simple, environmentally friendly, and can be widely applied to the preparation of van der Waals heterostructures such as metal-semiconductor and metal-insulator structures.

[0028] (1) Green and environmentally friendly, simple process: The sacrificial layer can be dissolved by deionized water. The whole process does not require toxic chemical reagents or harsh operating conditions, which significantly reduces manufacturing costs and safety risks.

[0029] (2) No interface damage: The transfer process is free from high-energy particle bombardment, reducing interface defects and chemical bond disorder, and optimizing the interface state density.

[0030] (3) Uniform film thickness and controllable size: The metal thin film prepared by high vacuum thermal evaporation maintains its original thickness and uniformity after transfer, which meets the requirements of precise electrode design.

[0031] (4) Wide material compatibility: It can realize the transfer of various metal thin films such as aluminum (Al), silver (Ag), gold (Au), and copper (Cu), and is suitable for different electronic devices and optoelectronic devices.

[0032] In some embodiments of the present invention, the thickness of the polyvinyl alcohol film is 100~300nm. For example, it includes 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm, or any sub-range composed of two of the above values.

[0033] In some embodiments of the present invention, the thickness of the polyvinyl alcohol film is 200-250 nm. For example, it includes 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, or any sub-range consisting of two of the above values.

[0034] In some embodiments of the present invention, the number-average molecular weight of the polyvinyl alcohol in the polyvinyl alcohol film is 70,000 to 130,000 g / mol. For example, it includes 70,000 g / mol, 72,600 g / mol, 75,000 g / mol, 81,400 g / mol, 85,000 g / mol, 90,000 g / mol, 95,000 g / mol, 101,200 g / mol, 110,000 g / mol, 124,000 g / mol, 130,000 g / mol, or any sub-range consisting of two of the above values.

[0035] In some embodiments of the present invention, in step S2, the thickness of the metal thin film is 10~500nm. For example, it includes 10nm, 20nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, or any sub-range composed of any two of the above values.

[0036] In some embodiments of the present invention, the metal in the metal film includes at least one of gold, aluminum, copper or silver.

[0037] In some embodiments of the present invention, in step S1, the coating method includes spin coating.

[0038] In some embodiments of the present invention, the spin coating speed is 2000~4000 rpm. For example, it includes 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm, 2800 rpm, 3000 rpm, 3200 rpm, 3400 rpm, 3600 rpm, 3800 rpm, 4000 rpm, or any sub-range of any two of the above values.

[0039] In some embodiments of the present invention, the spin coating time is 30 to 60 seconds. For example, it includes 30 seconds, 32 seconds, 35 seconds, 38 seconds, 40 seconds, 42 seconds, 45 seconds, 48 ​​seconds, 50 seconds, 52 seconds, 55 seconds, 58 seconds, 60 seconds, or any sub-range composed of any two of the above values.

[0040] In some embodiments of the present invention, the supporting substrate includes at least one of a quartz sheet, a glass sheet, a silicon wafer, or a silicon dioxide substrate.

[0041] In some embodiments of the present invention, the target substrate includes at least one of a quartz sheet, a glass sheet, or a semiconductor substrate.

[0042] Example 1 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 1 g of polyvinyl alcohol (PVA 17) PVA particles of type 88 (number average molecular weight 72600-81400 g / mol) were dissolved in 19 mL of deionized water to prepare a 5 wt% PVA solution and then filtered.

[0043] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated with PVA solution at 3500 rpm for 45 seconds and then dried on a hot plate.

[0044] A 20 nm gold film was deposited by evaporation (high vacuum thermal evaporation, power 579 W, time 1200 s, rate 0.165 Å / s) on a polyvinyl alcohol film (thickness approximately 220 nm).

[0045] The obtained product was placed in 65℃ deionized water to dissolve the polyvinyl alcohol film, and then the floating gold film was scooped up (as shown in the figure above). Figure 2 (As shown) to the target substrate.

[0046] Furthermore, SEM testing was performed on the gold thin film, and the results are as follows: Figure 3 As shown, the floating film is continuous and intact, and the gold film before and after transfer is free of cracks and defects in the SEM images.

[0047] Furthermore, AFM testing was performed on the gold thin film, and the results are as follows: Figure 5 As shown, the AFM results reveal that the floating gold film has a continuous and dense morphology with a root mean square roughness of 2.98 nm, indicating good uniformity.

[0048] Example 2 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 2 g of polyvinyl alcohol (PVA 17) Dissolve type 88 granules in 23 mL of deionized water to prepare an 8 wt% PVA solution and filter.

[0049] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated at 4000 rpm for 45 seconds and then dried.

[0050] A 30 nm thick Ag film was deposited by evaporation (high vacuum thermal evaporation, power 426 W, time 2105 s, rate 0.17 Å / s) on a polyvinyl alcohol film (thickness approximately 220 nm).

[0051] The prepared product was placed in deionized water at 80℃. The polyvinyl alcohol film dissolved rapidly, and the silver film floated on the surface before being scooped onto the target substrate. The floating silver film showed good integrity and no cracks (e.g., Figure 4 (As shown).

[0052] Example 3 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 1 g of polyvinyl alcohol (PVA 17) PVA granules (type 88) were dissolved in 19 mL of deionized water to prepare a 5 wt% PVA solution, which was then filtered.

[0053] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated with PVA solution at 3500 rpm for 45 seconds and then dried on a hot plate.

[0054] A 10 nm thick Au film was deposited on a polyvinyl alcohol film using high-vacuum thermal evaporation with parameters of 573 W power, 0.136 Å / s rate, and 800 s time.

[0055] The prepared product was placed in 70°C deionized water. The polyvinyl alcohol film dissolved rapidly, and the gold film floated on the water surface before being scooped onto a quartz substrate.

[0056] Example 4 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 1 g of polyvinyl alcohol (PVA 17) PVA granules (type 88) were dissolved in 19 mL of deionized water to prepare a 5 wt% PVA solution, which was then filtered.

[0057] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated with PVA solution at 3500 rpm for 45 seconds and then dried on a hot plate.

[0058] A 30 nm thick Au film was deposited on a polyvinyl alcohol film using high-vacuum thermal evaporation with parameters of 580 W power, 0.168 Å / s rate, and 1790 s time.

[0059] The prepared product was placed in 70°C deionized water. The polyvinyl alcohol film dissolved rapidly, and the gold film floated on the water surface before being scooped onto a quartz substrate.

[0060] Example 5 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 1 g of polyvinyl alcohol (PVA 17) PVA granules (type 88) were dissolved in 19 mL of deionized water to prepare a 5 wt% PVA solution, which was then filtered.

[0061] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated with PVA solution at 3500 rpm for 45 seconds and then dried on a hot plate.

[0062] A 40 nm thick Au film was deposited on a polyvinyl alcohol film using high-vacuum thermal evaporation with parameters of 582 W power, 0.171 Å / s rate, and 2280 s time.

[0063] The prepared product was placed in 70°C deionized water. The polyvinyl alcohol film dissolved rapidly, and the gold film floated on the water surface before being scooped onto a quartz substrate.

[0064] Example 6 This example provides a method for preparing van der Waals metal thin films, including the following steps: Weigh 1 g of polyvinyl alcohol (PVA 17) PVA granules (type 88) were dissolved in 19 mL of deionized water to prepare a 5 wt% PVA solution, which was then filtered.

[0065] Via ultraviolet The Si-supported substrate, which was treated with ozone for 15 minutes, was spin-coated with PVA solution at 3500 rpm for 45 seconds and then dried on a hot plate.

[0066] A 50 nm thick Au film was deposited on a polyvinyl alcohol film using high-vacuum thermal evaporation with parameters of 586 W power, 0.185 Å / s rate, and 2700 s time.

[0067] The prepared product was placed in 70°C deionized water. The polyvinyl alcohol film dissolved rapidly, and the gold film floated on the water surface before being scooped onto a quartz substrate.

[0068] Comparative Example 1 Comparative Example 1 deposited Au films of 20 nm, 10 nm, 30 nm, 40 nm and 50 nm thicknesses directly on a cleaned quartz substrate using high-vacuum thermal evaporation (with the same deposition parameters as in Examples 1, 3, 4, 5 and 6).

[0069] Performance testing The electrical properties of gold thin films of different thicknesses prepared in Examples 1, 3-6, and Comparative Example 1 were tested. The results are as follows: Figure 6 As shown, where Figure 6 In this context, A represents resistivity. Figure 6In this figure, B represents light transmittance. In contrast, floating gold films of various thicknesses exhibit superior electrical properties, characterized by a decrease in resistivity (obtained by the four-probe method), for example, at a thickness of 10 nm, the resistivity decreases from 375.76 Ω / sq for directly deposited gold films to 182.10 Ω / sq for floating gold films; and an increase in light transmittance (obtained by a UV-Vis spectrophotometer), for example, at a thickness of 10 nm, the visible light transmittance increases from 39.06% for directly deposited gold films to 46.61% for floating gold films.

[0070] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing van der Waals metal thin films, characterized in that, Includes the following steps: S1. Coat the surface of the support substrate with a polyvinyl alcohol film; S2. A metal film is deposited on the surface of the polyvinyl alcohol film to obtain an intermediate; S3. The intermediate is placed in water at 60~80℃ to remove the polyvinyl alcohol film and obtain a floating metal film; The metal thin film is transferred to the surface of the target substrate and bonded together by van der Waals forces.

2. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, The thickness of the polyvinyl alcohol film is 100~300nm.

3. The method for preparing van der Waals metal thin films according to claim 1 or 2, characterized in that, The thickness of the polyvinyl alcohol film is 200~250nm.

4. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, The number-average molecular weight of polyvinyl alcohol in the polyvinyl alcohol film is 70,000~130,000 g / mol.

5. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, In step S2, the thickness of the metal thin film is 10~500nm.

6. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, The metal in the metal film includes at least one of gold, aluminum, copper, or silver.

7. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, In step S1, the coating method includes spin coating; and / or, the spin coating speed is 2000~4000 rpm.

8. The method for preparing van der Waals metal thin films according to claim 7, characterized in that, The spin coating time is 30-60 seconds.

9. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, The supporting substrate includes at least one of a quartz sheet, a glass sheet, a silicon wafer, or a silicon dioxide substrate.

10. The method for preparing van der Waals metal thin films according to claim 1, characterized in that, The target substrate includes at least one of a quartz sheet, a glass sheet, or a semiconductor substrate.

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