Wrinkle-free two-dimensional atomic crystal film transfer method based on hydrophilic aluminum oxide auxiliary layer

Abstract

The invention provides a wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer. The method comprises the specific steps that an aluminum oxide film is deposited on a target substrate through atomic layer deposition in a standard semiconductor technology; spin-coating polymethyl methacrylate (PMMA) on the substrate on which the two-dimensional material grows; etching the substrate by the etchant solution, so that the PMMA / two-dimensional material is separated from the substrate and floats on the solution; cleaning for multiple times, fishing up with a target substrate, airing, exhausting air and baking; and removing PMMA with acetone to obtain the wrinkle-free two-dimensional material / target substrate. According to the method, due to the existence of the aluminum oxide layer, the surface of the target substrate has high hydrophilicity, the thin film is better attached to the substrate during transferring, the thin film can be effectively prevented from being folded, and large-area wrinkle-free transferring of the thin film is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional material transfer, and in particular relates to a wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer. Background Art

[0002] Due to their atomic-level thickness and unique physical and chemical properties, two-dimensional materials have shown great potential in the fields of electronics, optoelectronics, energy, catalysis and sensing. Materials such as graphene and transition metal dichalcogenides (such as MoS2) have high carrier mobility, adjustable band gap, high transparency and excellent mechanical properties, providing an ideal platform for new devices (such as high-performance transistors, flexible electronics, photodetectors, etc.). However, the practical application of two-dimensional materials faces challenges, especially materials grown by chemical vapor deposition (CVD) require a high temperature environment and are incompatible with semiconductor processes. For this reason, wet transfer technology has become a key solution. Wet transfer can transfer high-temperature grown two-dimensional materials from a growth substrate (such as copper foil) to a target substrate (such as SiO2 / Si, a flexible substrate or a substrate that cannot withstand the high temperature of CVD growth), avoiding the negative impact of high temperature on the device while maintaining the high quality of the material, supporting multilayer stacking and heterogeneous structure construction, and in addition, compared with dry transfer, wet transfer has a lower cost and can be transferred over a large area, which is suitable for large-scale production and device manufacturing. Therefore, in order to achieve the widespread application of two-dimensional materials, a wrinkle-free wet transfer technology is very important. Summary of the invention

[0003] The object of the present invention is to provide a wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer.

[0004] Based on this, the method provided by the present invention has the following specific steps:

[0005] Step 1: Deposit a layer of aluminum oxide film on a cleaned target substrate using atomic layer deposition in a standard semiconductor process;

[0006] Step 2: Spin-coat polymethyl methacrylate (PMMA) on the substrate (PdSe2-SiO2 / Si substrate) on which the two-dimensional material is grown, dry it, and scrape off the edge of the PMMA film;

[0007] Step 3: Prepare a concentrated corrosion solution (HF solution) and pour it into a polytetrafluoroethylene culture dish. The bottom of the culture dish is not completely covered by the solution, leaving half of the area dry;

[0008] Step 4: Place the PMMA-coated PdSe2-SiO2 / Si substrate in a dry place in a petri dish, slowly bring one corner of it close to the HF solution, and wait for PMMA / PdSe2 to separate from the substrate and float above the solution;

[0009] Step 5: Transfer PMMA / PdSe2 to deionized water for cleaning, remove the corrosive solution, and pick it up with the target substrate;

[0010] Step 6: Use dust-free paper to absorb moisture from the surface of the substrate, place it at an angle to dry naturally, put it in a vacuum dryer for degassing, and bake it at 100°C for 20 minutes;

[0011] Step 7: Place the substrate in an acetone solution, remove the PMMA, and blow dry to obtain a wrinkle-free PdSe2-target substrate.

[0012] Furthermore, in step 1, the thickness of the aluminum oxide film is 10 to 30 nm.

[0013] Furthermore, the spin coating and baking parameters of PMMA in step 2 are: 800 rpm, 10 s; 5000 rpm, 50 s; 170°C, 5 min. Repeat twice. The size of the two-dimensional material to be transferred is 0.1×0.1~1.5×1.5 cm 2 , thickness is 0.8~25nm.

[0014] Furthermore, in step 5, the PMMA / PdSe2 residual liquid is cleaned in ionized water for 3 to 5 times.

[0015] Furthermore, in step 6, the time for natural drying by tilting is 4 to 6 hours; the vacuum degree of the exhaust treatment is 0.1 Pa, and the time is 20 to 40 minutes; the baking temperature is 100° C., and the time is 20 to 30 minutes.

[0016] Furthermore, in step 7, the substrate is placed in the acetone solution for 20 to 30 minutes.

[0017] The present invention provides a wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer, and the specific method is: using atomic layer deposition in a standard semiconductor process to deposit a layer of aluminum oxide film on a target substrate; spin coating polymethyl methacrylate (PMMA) on a substrate with a two-dimensional material grown thereon; etching the substrate with a corrosive solution to separate the PMMA / two-dimensional material from the substrate and float on the solution; washing multiple times, scooping it up with a target substrate, drying, evacuating, and baking; using acetone to remove the PMMA to obtain a wrinkle-free two-dimensional material / target substrate. Compared with the prior art, the advantages of this method are: the presence of the aluminum oxide layer makes the surface of the target substrate highly hydrophilic, the film fits the substrate better during transfer, and the film can be effectively prevented from folding, thereby achieving large-area wrinkle-free transfer of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1Atomic force microscopy image of the transferred PdSe2 film results.

[0020] Figure 2 Atomic force microscopy image of the transferred WS2 film results. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific examples.

[0022] Example 1

[0023] A wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer comprises the following steps:

[0024] Step 1: Deposit a 30nm aluminum oxide film on the cleaned target substrate using atomic layer deposition in a standard semiconductor process;

[0025] Step 2: On the substrate with two-dimensional material (PdSe2-SiO2 / Si substrate, PdSe2 film size is 1×1cm 2 , with a thickness of 4.5 nm. ) was spin-coated with polymethyl methacrylate (PMMA), and the PMMA film was dried and scraped off at the edge. The parameters were: 800 rpm, 10 s; 5000 rpm, 50 s; 170 ° C, 5 min, and repeated twice;

[0026] Step 3: Prepare a concentrated corrosion solution (HF solution) and pour it into a polytetrafluoroethylene culture dish. The bottom of the culture dish is not completely covered by the solution, leaving half of the area dry;

[0027] Step 4: Place the PMMA-coated PdSe2-SiO2 / Si substrate in a dry place in a petri dish, slowly bring one corner of it close to the HF solution, and wait for PMMA / PdSe2 to separate from the substrate and float above the solution;

[0028] Step 5: Transfer PMMA / PdSe2 to deionized water and wash it 5 times to remove the etching solution and pick it up with the target substrate;

[0029] Step 6: Use dust-free paper to absorb the moisture on the surface of the substrate, place it at an angle to dry it naturally for 6 hours, put it in a vacuum dryer for degassing (0.1 Pa, 30 minutes), and bake it at 100°C for 20 minutes;

[0030] Step 7: Soak the substrate in acetone solution for 20 minutes, remove PMMA, and blow dry to obtain a wrinkle-free PdSe2-target substrate.

[0031] Figure 1 Atomic force microscopy image of the transferred PdSe2 film. Figure 1It can be seen that the surface of the PdSe2 film transferred by this method is smooth and wrinkle-free, and the root mean square roughness is only 0.28nm.

[0032] Example 2

[0033] A wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer comprises the following steps:

[0034] Step 1: Deposit a 20nm aluminum oxide film on the cleaned target substrate using atomic layer deposition in a standard semiconductor process;

[0035] Step 2: On a substrate with two-dimensional material (WS2-Sapphire substrate, WS2 film size 0.2×0.2cm 2 , with a thickness of 0.86 nm. ) was spin-coated with polymethyl methacrylate (PMMA), and the PMMA film was dried and scraped off at the edge. The parameters were: 800 rpm, 10 s; 5000 rpm, 50 s; 170 ° C, 5 min, and repeated twice;

[0036] Step 3: Prepare a concentrated corrosion solution (potassium hydroxide solution) and pour it into the culture dish. The bottom of the culture dish is not completely covered by the solution, leaving half of the area dry;

[0037] Step 4: Place the PMMA-coated WS2-Sapphire substrate in a dry place in the petri dish, slowly bring one corner of it closer to the solution, and wait for the PMMA / WS2 to separate from the substrate and float above the solution;

[0038] Step 5: Transfer PMMA / WS2 to deionized water and wash it 5 times to remove the corrosive solution and pick it up with the target substrate;

[0039] Step 6: Use dust-free paper to absorb the moisture on the surface of the substrate, place it at an angle to dry it naturally for 6 hours, put it in a vacuum dryer for degassing (0.1 Pa, 30 minutes), and bake it at 100°C for 20 minutes;

[0040] Step 7: Soak the substrate in acetone solution for 20 minutes, remove PMMA, and blow dry to obtain a wrinkle-free WS2-target substrate.

[0041] Figure 2 Atomic force microscopy image of the transferred WS2 film. Figure 2 It can be seen that the surface of the WS2 film transferred by this method is smooth and wrinkle-free, and the root mean square roughness is only 0.26nm.

[0042] The above embodiments are only examples for explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modification, equivalent substitution and improvement within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer, comprising the following steps: Step 1: Deposit a layer of aluminum oxide film on a cleaned target substrate using atomic layer deposition in a standard semiconductor process; Step 2: Spin-coat polymethyl methacrylate (PMMA) on the substrate (PdSe2-SiO2 / Si substrate) on which the two-dimensional material is grown, dry it, and scrape off the edge of the PMMA film; Step 3: Prepare a concentrated corrosion solution (HF solution) and pour it into a polytetrafluoroethylene culture dish. The bottom of the culture dish is not completely covered by the solution, leaving half of the area dry; Step 4: Place the PMMA-coated PdSe2-SiO2 / Si substrate in a dry place in a petri dish, slowly bring one corner of it close to the HF solution, and wait for PMMA / PdSe2 to separate from the substrate and float above the solution; Step 5: Transfer PMMA / PdSe2 to deionized water for cleaning, remove the corrosive solution, and pick it up with the target substrate; Step 6: Use dust-free paper to absorb moisture from the surface of the substrate, place it at an angle to dry naturally, put it in a vacuum dryer for degassing, and bake it at 100°C for 20 minutes; Step 7: Place the substrate in an acetone solution, remove the PMMA, and blow dry to obtain a wrinkle-free PdSe2-target substrate.

2. A wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer according to claim 1, characterized in that: In step 1, the thickness of the aluminum oxide film is 10 to 30 nm.

3. The wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer according to claim 1, characterized in that: The spin-coated PMMA and baking parameters in step 2 are: 800 rpm, 10 s; 5000 rpm, 50 s; 170°C, 5 min. The size of the two-dimensional material to be transferred is 0.1×0.1~1.5×1.5 cm 2 , thickness is 0.8~25nm.

4. The wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer according to claim 1, characterized in that: In step 5, the PMMA / PdSe2 residual solution is cleaned in deionized water for 3 to 5 times.

5. The wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer according to claim 1, characterized in that: In step 6, the time for natural drying by tilting is 4 to 6 hours; the vacuum degree of the exhaust treatment is 0.1 Pa, and the time is 20 to 40 minutes; the baking temperature is 100° C., and the time is 20 to 30 minutes.

6. The wrinkle-free two-dimensional atomic crystal film transfer method based on a hydrophilic aluminum oxide auxiliary layer according to claim 1, characterized in that: In step 7, the substrate is placed in the acetone solution for 20 to 30 minutes.

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