A preparation method for high-mobility p-type two-dimensional WS2

Abstract

The present invention relates to a method for preparing a high-mobility p-type two-dimensional WS2, as well as a high-mobility p-type two-dimensional WS2 and its application. By using WO3 and S as reaction precursors for preparing WS2, and using ammonia water as a solvent for liquid phase assistance, the secondary nucleation and longitudinal growth of WS2 are suppressed, and the lateral growth of WS2 is promoted, which is more conducive to the preparation of large-sized, single-layer two-dimensional WS2. Spatial confinement is used to provide a sufficient precursor source for the growth process of two-dimensional WS2. Since the reaction is carried out under S-rich conditions, a certain amount of W vacancies will exist in the two-dimensional WS2, thereby introducing an acceptor energy level, so that the two-dimensional WS2 exhibits p-type conductive characteristics. The p-type field-effect transistor prepared with the two-dimensional WS2 prepared by the present invention has high hole mobility and a large switching ratio.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional material applications, and relates to a preparation method of high-mobility p-type two-dimensional WS2, as well as high-mobility p-type two-dimensional WS2 and its application. Background Art

[0002] Two-dimensional materials refer to materials in which electrons can move freely only in two non-nanoscale dimensions. Their atomic arrangement, size, bond energy, etc. are similar in two dimensions and are significantly stronger than third-dimensional nanomaterials. In 2004, researchers from the University of Manchester used tape to mechanically peel off a single layer of graphene from a graphite block, verifying that two-dimensional materials can exist stably at room temperature. In recent years, two-dimensional transition metal dichalcogenides (TMDCs) have been widely regarded as promising star materials for future electronic device applications due to their graphene-like two-dimensional structure. Compared with traditional silicon transistors, TMDCs, as direct bandgap semiconductors with strong spin-orbit interactions, exhibit excellent electronic and mechanical properties in fields such as spintronics, optoelectronics, and flexible electronics. They also overcome the obstacles to further miniaturization of silicon transistors, such as high contact resistance, short channel effects, and high leakage current. Theoretical calculations have found that, considering the long-term acoustic and optical wave scattering of carriers, WS2 has the highest hole mobility of 540 cm among more than ten TMDCs materials. 2 V -1 s -1 Moreover, due to its advantages such as high carrier mobility, high thermal stability, high exciton binding energy, electrostatic integrity and no dangling bonds, WS2 has now become an ideal candidate material for field effect transistors (FETs).

[0003] Currently, single-layer two-dimensional WS2 is primarily produced using CVD. However, most WS2 produced using this method exhibits n-type conductivity, while the CVD production of high-mobility p-type 2D WS2 has rarely been reported. This significantly limits its application in logic complementary circuits. Currently, p-type 2D WS2 is primarily produced using methods such as chemical doping and electrostatic doping.

[0004] Contact engineering is a strategy used in the fabrication of two-dimensional WS2 devices. It optimizes the device's electron and hole injection efficiency by adjusting the Fermi level at the metal / semiconductor interface by selecting metal contact materials with different work functions. Contact engineering can reduce the Schottky barrier height, resulting in a more balanced electron and hole transport and improved performance of two-dimensional WS2 devices. However, in some cases, contact engineering can introduce new interface states that can trap or scatter carriers, thereby affecting the performance of two-dimensional WS2 devices.

[0005] Chemical doping is a common method for obtaining p-type semiconductors. Some researchers have grown WS2 using CVD and then doped CH units (such as -CH3, -CH2-CH3) into WS2 using PECVD, reducing the number of S vacancies in WS2 and achieving a transition from n-type to p-type conductivity. However, due to the non-selective adsorption of dopants on the TMD channel surface, performance degradation may occur at the interface.

[0006] Electrostatic doping is another common method for achieving p-type conductivity in two-dimensional semiconductor devices. Research has found that different regions of a WS2 nanosheet can be manipulated to have n-type or p-type conductivity through electrostatic doping, achieving an in-plane PN junction within a single WS2 nanosheet. However, the effectiveness of electrostatic doping can be affected by environmental conditions, and its long-term stability is inferior to that of chemical doping. Furthermore, in some cases, the electric field may induce new interface states, affecting device performance.

[0007] Despite some progress in the preparation of p-type two-dimensional WS2, the three aforementioned fabrication methods still have limitations. Field-effect transistors fabricated using contact engineering and electrostatic doping typically have complex structures and place high demands on the device fabrication process. Furthermore, the dopant atoms used in chemical doping can cause lattice distortion, affecting the electronic structure and transport properties. Therefore, improving fabrication methods to directly synthesize high-quality p-type two-dimensional WS2 is crucial for the development of next-generation novel logic complementary circuits. Summary of the Invention

[0008] Technical problems to be solved

[0009] To overcome the shortcomings of the prior art, the present invention proposes a method for preparing high-mobility p-type two-dimensional WS2, as well as applications of high-mobility p-type two-dimensional WS2. This method employs a novel liquid-phase-assisted spatially confined CVD method to produce large-scale, single-layer, p-type two-dimensional WS2 nanosheets by regulating process parameters such as deposition temperature and precursor solution concentration. This method offers advantages such as strong controllability, stable process, and high production efficiency. Furthermore, the two-dimensional WS2 exhibits high hole mobility, resolving the low hole mobility issue of two-dimensional WS2 produced by existing methods. This method provides valuable insights for the preparation of high-quality p-type two-dimensional semiconductors.

[0010] Technical Solution

[0011] A method for preparing high-mobility p-type two-dimensional WS2, characterized by the following steps:

[0012] Step 1: Prepare a WO3 precursor solution using ammonia as a solvent and WO3;

[0013] Step 2: Drop 0.3-0.5 ml of the precursor solution onto the SiO2 surface of the SiO2 / Si substrate;

[0014] Step 3: Dry the substrate at a temperature of 80-100°C. Place the substrate in a sleeve. Cover the substrate with another SiO2 / Si substrate and push both into the quartz tube.

[0015] Step 4: Place a quartz boat on one side of the sleeve in the direction of carrier gas introduction; the quartz boat contains S powder;

[0016] Step 5: Place the quartz tube in a single-temperature zone tube furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 6-10 Pa; then introduce high-purity Ar gas at a flow rate of 180-220 sccm for 5-10 minutes to return the quartz tube to normal pressure;

[0017] Step 6: Under normal pressure, adjust the Ar gas flow rate to 80-120 sccm, set the temperature control program of the single-zone tubular furnace, first heat the sleeve to 500-600°C, keep it warm for 10-25 minutes, and adjust the Ar gas flow rate to 30-60 sccm at the end of the insulation;

[0018] Step 7: When the casing is heated to 700-850°C, the heating belt of the sulfur powder is turned on and the temperature of the heating belt is set to 130-180°C; the casing is then heated to 900-1000°C, and the sulfur powder is also heated to the preset temperature.

[0019] Step 8: Adjust the Ar gas to 20-30 sccm, introduce 10-20 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 8-15 minutes; turn off the heating device and cool to room temperature with the furnace to obtain high-mobility p-type two-dimensional WS2 on the SiO2 surface of the SiO2 / Si substrate.

[0020] The SiO2 / Si substrate is ultrasonically cleaned with acetone, ethanol and deionized water for 10 to 20 minutes respectively, and then the SiO2 / Si substrate is blown dry.

[0021] The WO3 precursor solution has a WO3 concentration of 0.01 to 0.3 g / ml.

[0022] When preparing the WO3 precursor solution, 0.1-0.6g WO3 is prepared with ammonia water with a concentration of 10-30% and a volume of 1-100ml.

[0023] The amount of S powder in the quartz boat is 50-70 mg.

[0024] The position distribution of the substrate and the quartz boat is 2-4 cm between the quartz boat and the sleeve, 2-8 cm between the substrate in one side of the sleeve and the end of the sleeve, and 20-30 cm between the other side of the sleeve and the end of the quartz tube.

[0025] The step 3 is to place the substrate on a heating plate and dry it.

[0026] A high-mobility p-type two-dimensional WS2 prepared by the preparation method is characterized in that: the p-type two-dimensional WS2 nanosheet is a single layer, the WS2 grows laterally to achieve a large size, and there are W vacancies in the WS2, thereby introducing acceptor energy levels, so that the two-dimensional WS2 exhibits p-type conductive properties.

[0027] An application of the high-mobility p-type two-dimensional WS2 is characterized in that it is used to prepare a p-type field-effect transistor.

[0028] The hole mobility of the p-type field-effect transistor prepared with two-dimensional WS2 as the active layer is as high as 46.87 cm 2 V -1 s -1 , the on / off ratio is 10 5 , showing excellent p-type field-effect transistor characteristics.

[0029] Beneficial effects

[0030] This invention proposes a method for preparing high-mobility p-type two-dimensional WS2, as well as applications of high-mobility p-type two-dimensional WS2. The method utilizes WO3 and S as precursors for the WS2 reaction, employs ammonia as a liquid-phase solvent, and utilizes a cannula with a small hole at the bottom and a valve on the right side for spatial confinement. During the chemical reaction, ammonia reacts with tungsten oxide to form a tungsten ammonia complex, inhibiting secondary nucleation and longitudinal growth of WS2 while promoting lateral growth, thereby facilitating the preparation of large-scale, single-layer two-dimensional WS2. The cannula with a small hole at the bottom and a valve on the right side for spatial confinement concentrates S vapor and H2 gas within the cannula, creating a concentration field rich in S and H2 precursors that is in full contact with the substrate surface, providing ample precursor sources for the growth of the two-dimensional WS2. Because the reaction proceeds under S-rich conditions, a certain number of W vacancies are present in the two-dimensional WS2, introducing acceptor energy levels and imparting p-type conductivity to the two-dimensional WS2. The p-type field effect transistor prepared using the two-dimensional WS2 prepared by the present invention has high hole mobility and a large switching ratio.

[0031] The main innovative features of the present invention are:

[0032] (1) The present invention requires a small amount of equipment and only requires a tube furnace to grow two-dimensional WS2, and the experimental process is easy to operate;

[0033] (2) The present invention uses ammonia as the solvent of the liquid-phase assisted method. During the reaction, ammonia can form a tungsten ammonia oxide complex with tungsten oxide, which inhibits the secondary nucleation and longitudinal growth of WS2 and promotes the lateral growth of WS2, thereby realizing the preparation of large-scale, single-layer two-dimensional WS2;

[0034] (3) The present invention uses a sleeve with a small hole at the bottom and a valve on the right side to create a concentration field rich in S and H2 precursor sources, ensuring the effective supply of precursor sources during the two-dimensional WS2 deposition process;

[0035] (4) The two-dimensional WS2 deposition process of the present invention is carried out under S-rich conditions, so that WS2 contains a certain amount of W vacancies, so that the prepared two-dimensional WS2 exhibits p-type conductive properties;

[0036] (5) The present invention prepares two-dimensional WS2 on the SiO2 surface of the SiO2 / Si substrate. The prepared two-dimensional WS2 does not need to be transferred, and the substrate can be directly used to prepare field-effect transistors, avoiding the tedious transfer process;

[0037] (6) Using the two-dimensional WS2 of the present invention as the active layer, the hole mobility of the prepared p-type field-effect transistor is as high as 46.87 cm 2 V -1 s -1 , the on / off ratio is 10 5 , showing excellent p-type field-effect transistor characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : Schematic diagram of the reaction apparatus.

[0039] Figure 2 : AFM test image of grown WS2 nanosheets.

[0040] Figure 3 : STEM test image of grown WS2 nanosheets.

[0041] Figure 4 : Semi-logarithmic coordinate transfer characteristic curve of WS2 field effect transistor.

[0042] Figure 3 The white bright spots in the middle represent W atoms. Through observation, it was found that the originally regularly arranged white bright spots disappeared in certain positions, indicating that there are certain W atomic vacancies in the WS2 prepared in this experiment. The existence of W vacancies causes the prepared single-layer two-dimensional WS2 to exhibit p-type conductive properties. DETAILED DESCRIPTION

[0043] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0044] The present invention adopts a novel liquid-phase assisted spatial confinement CVD method to prepare large-size, single-layer, p-type two-dimensional WS2 nanosheets by regulating process parameters such as deposition temperature and precursor solution concentration.

[0045] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0046] (1) The SiO2 / Si substrate was ultrasonically cleaned with acetone, ethanol, and deionized water for 10 to 20 minutes, and then the SiO2 / Si substrate was blown dry for later use.

[0047] (2) Weigh 0.1-0.6 g of WO3 and use 10-30% ammonia water in a volume of 1-100 ml as a solvent to prepare a precursor solution with a WO3 concentration of 0.01-0.3 g / ml.

[0048] (3) Use a small dropper to take the prepared precursor solution and drop 0.3-0.5 ml on the SiO2 surface of the SiO2 / Si substrate.

[0049] (4) Place the substrate on a heating plate and dry it at a temperature of 80-100° C. Then, place the substrate 2-8 cm away from the left end of the sleeve.

[0050] (5) Take another clean SiO2 / Si substrate and place it parallel to the above substrate with the SiO2 surface facing downwards. Then slowly push the sleeve into the quartz tube to a position 20 to 30 cm away from the right end.

[0051] (6) Weigh 50-70 mg of S powder into a quartz boat and push the quartz boat into the quartz tube, 2-4 cm away from the left end of the sleeve.

[0052] (7) Place the quartz tube in a single-temperature zone tubular furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 6 to 10 Pa.

[0053] (8) High-purity Ar gas at a flow rate of 180-220 sccm is introduced into the quartz tube for 5-10 minutes to bring the inside of the quartz tube to normal pressure.

[0054] (9) Under normal pressure, adjust the Ar gas flow rate to 80-120 sccm, set the temperature control program of the single-zone tubular furnace, first heat the sleeve to 500-600℃, keep it warm for 10-25 minutes, and adjust the Ar gas flow rate to 30-60 sccm at the end of the insulation.

[0055] (10) When the casing is heated to 700-850°C, the heating belt of the sulfur powder is turned on and the temperature of the heating belt is set to 130-180°C.

[0056] (11) The casing is then heated to 900-1000°C, and the sulfur powder is simultaneously heated to the preset temperature.

[0057] (12) Adjust the Ar gas to 20-30 sccm, introduce 10-20 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 8-15 minutes.

[0058] (13) Turn off the heating device, cool to room temperature with the furnace, and take out the sample. Specific implementation method:

[0060] Example 1:

[0061] (1) The SiO2 / Si substrate was ultrasonically cleaned with acetone, ethanol, and deionized water for 10 min respectively, and then the SiO2 / Si substrate was blown dry for later use.

[0062] (2) Weigh 0.1 g of WO3 and use 10% ammonia water with a volume of 1 ml as a solvent to prepare a precursor solution with a WO3 concentration of 0.01 g / ml.

[0063] (3) Use a small dropper to take the prepared precursor solution and drop 0.3 ml on the SiO2 surface of the SiO2 / Si substrate.

[0064] (4) Place the substrate on a hot plate and dry it at 80° C. Then, place the substrate 2 cm away from the left end of the cannula.

[0065] (5) Take another clean SiO2 / Si substrate and place it parallel to the above substrate with the SiO2 surface facing downwards. Then slowly push the sleeve into the quartz tube to a position 20 cm away from the right end.

[0066] (6) Weigh 50 mg of S powder into a quartz boat and push the quartz boat into the quartz tube, 2 cm away from the left end of the sleeve.

[0067] (7) Place the quartz tube in a single-temperature zone tubular furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 6 Pa.

[0068] (8) High-purity Ar gas at a flow rate of 180 sccm is introduced into the quartz tube until the inside of the quartz tube is maintained at normal pressure.

[0069] (9) Maintaining normal pressure, adjust the Ar gas flow rate to 80 sccm, set the temperature control program of the single-temperature zone tubular furnace, first heat the sleeve to 500°C, then keep it warm for 10 minutes, and adjust the Ar gas flow rate to 30 sccm at the end of the insulation.

[0070] (10) When the casing is heated to 700°C, the heating belt of the sulfur powder is turned on and the temperature is set to 130°C.

[0071] (11) The casing is then heated to 900°C, and the sulfur powder is simultaneously heated to the preset temperature.

[0072] (12) Adjust the Ar gas to 20 sccm, introduce 10 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 8 minutes.

[0073] (13) Turn off the heating device, cool to room temperature with the furnace, and take out the sample.

[0074] Example 2:

[0075] (1) The SiO2 / Si substrate was ultrasonically cleaned with acetone, ethanol, and deionized water for 20 min respectively, and then the SiO2 / Si substrate was blown dry for later use.

[0076] (2) Weigh 0.6 g of WO3 and use 30% ammonia water with a volume of 100 ml as solvent to prepare a precursor solution with a WO3 concentration of 0.3 g / ml.

[0077] (3) Use a small dropper to take the prepared precursor solution and drop 0.4 ml on the SiO2 surface of the SiO2 / Si substrate.

[0078] (4) Place the substrate on a hot plate and dry it at 90° C. Then, place the substrate 5 cm away from the left end of the cannula.

[0079] (5) Take another clean SiO2 / Si substrate and place it parallel to the above substrate with the SiO2 surface facing downwards. Then slowly push the sleeve into the quartz tube to a position 30 cm away from the right end.

[0080] (6) Weigh 70 mg of S powder into a quartz boat and push the quartz boat into the quartz tube, 4 cm away from the left end of the sleeve.

[0081] (7) Place the quartz tube in a single-temperature zone tubular furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 8 Pa.

[0082] (8) High-purity Ar gas at a flow rate of 200 sccm is introduced into the quartz tube until the inside of the quartz tube is maintained at normal pressure.

[0083] (9) Maintaining normal pressure, adjust the Ar gas flow rate to 120 sccm, set the temperature control program of the single-zone tubular furnace, first heat the sleeve to 550°C, then keep it warm for 20 minutes, and adjust the Ar gas flow rate to 50 sccm at the end of the insulation.

[0084] (10) When the casing is heated to 850°C, the heating belt of the sulfur powder is turned on and the temperature is set to 180°C.

[0085] (11) The casing is then heated to 1000°C, and the sulfur powder is simultaneously heated to the preset temperature.

[0086] (12) Adjust the Ar gas to 30 sccm, introduce 20 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 15 minutes.

[0087] (13) Turn off the heating device, cool to room temperature with the furnace, and take out the sample.

[0088] Example 3:

[0089] (1) The SiO2 / Si substrate was ultrasonically cleaned with acetone, ethanol, and deionized water for 15 min respectively, and then the SiO2 / Si substrate was blown dry for later use.

[0090] (2) Weigh 0.3 g of WO3 and use 50 ml of 20% ammonia water as a solvent to prepare a precursor solution with a WO3 concentration of 0.1 g / ml.

[0091] (3) Use a small dropper to take the prepared precursor solution and drop 0.5 ml on the SiO2 surface of the SiO2 / Si substrate.

[0092] (4) Place the substrate on a heating plate and dry it at 90° C. Then, place the substrate 8 cm away from the left end of the cannula.

[0093] (5) Take another clean SiO2 / Si substrate and place it parallel to the above substrate with the SiO2 surface facing downwards. Then slowly push the sleeve into the quartz tube to a position 25 cm away from the right end.

[0094] (6) Weigh 60 mg of S powder into a quartz boat and push the quartz boat into the quartz tube, 3 cm away from the left end of the sleeve.

[0095] (7) Place the quartz tube in a single-temperature zone tubular furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 10 Pa.

[0096] (8) High-purity Ar gas at a flow rate of 200 sccm is introduced into the quartz tube until the inside of the quartz tube is maintained at normal pressure.

[0097] (9) Maintaining normal pressure, adjust the Ar gas flow rate to 120 sccm, set the temperature control program of the single-zone tubular furnace, first heat the sleeve to 550°C, then keep it warm for 25 minutes, and adjust the Ar gas flow rate to 30 sccm at the end of the insulation.

[0098] (10) When the casing is heated to 775°C, the heating belt of the sulfur powder is turned on and the temperature is set to 150°C.

[0099] (11) The sleeve is then heated to 960°C, and the sulfur powder is simultaneously heated to the preset temperature.

[0100] (12) Adjust the Ar gas to 25 sccm, introduce 15 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 12 minutes.

[0101] (13) Turn off the heating device, cool to room temperature with the furnace, and take out the sample.

[0102] This method has the advantages of strong controllability, stable process, and high preparation efficiency. The two-dimensional WS2 has high hole mobility, which solves the problem of low hole mobility of two-dimensional WS2 prepared by existing methods, and provides useful reference value for the preparation of high-quality p-type two-dimensional semiconductors.

Claims

1. A method for preparing high-mobility p-type two-dimensional WS2, characterized in that Here are the steps: Step 1: Prepare a WO3 precursor solution using ammonia as a solvent and WO3; Step 2: Drop 0.3-0.5 ml of the precursor solution onto the SiO2 surface of the SiO2 / Si substrate; Step 3: Dry the substrate at a temperature of 80-100°C. Place the substrate in a sleeve. Cover the substrate with another SiO2 / Si substrate and push both into the quartz tube. Step 4: Place a quartz boat on one side of the sleeve in the direction of carrier gas introduction; the quartz boat contains S powder; Step 5: Place the quartz tube in a single-temperature zone tube furnace, tighten the flanges at both ends of the quartz tube, and evacuate the quartz tube to a pressure of 6-10 Pa; then introduce high-purity Ar gas at a flow rate of 180-220 sccm for 5-10 minutes to return the quartz tube to normal pressure; Step 6: Under normal pressure, adjust the Ar gas flow rate to 80-120 sccm, set the temperature control program of the single-zone tubular furnace, first heat the sleeve to 500-600°C, keep it warm for 10-25 minutes, and adjust the Ar gas flow rate to 30-60 sccm at the end of the insulation; Step 7: When the casing is heated to 700-850°C, the heating belt of the sulfur powder is turned on and the temperature of the heating belt is set to 130-180°C; the casing is then heated to 900-1000°C, and the sulfur powder is also heated to the preset temperature. Step 8: Adjust the Ar gas to 20-30 sccm, introduce 10-20 sccm of high-purity H2 gas, and at the same time close the valve on the right side of the sleeve, and maintain the deposition conditions for 8-15 minutes; turn off the heating device and cool to room temperature with the furnace to obtain high-mobility p-type two-dimensional WS2 on the SiO2 surface of the SiO2 / Si substrate.

2. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1, characterized in that: The SiO2 / Si substrate is ultrasonically cleaned with acetone, ethanol and deionized water for 10 to 20 minutes respectively, and then the SiO2 / Si substrate is blown dry.

3. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1, characterized in that: The WO3 precursor solution has a WO3 concentration of 0.01 to 0.3 g / ml.

4. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1 or 3, characterized in that: When preparing the WO3 precursor solution, 0.1-0.6g WO3 is prepared with ammonia water with a concentration of 10-30% and a volume of 1-100ml.

5. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1, characterized in that: The amount of S powder in the quartz boat is 50-70 mg.

6. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1, characterized in that: The position distribution of the substrate and the quartz boat is that the quartz boat is 2 to 4 cm away from the left end of the sleeve, the substrate in this side of the sleeve is 2 to 8 cm away from the end of the sleeve, and the other side of the sleeve is 20 to 30 cm away from the end of the quartz tube.

7. The method for preparing a high-mobility p-type two-dimensional WS2 according to claim 1, characterized in that: The step 3 is to place the substrate on a heating plate and dry it.

8. A high-mobility p-type two-dimensional WS2 prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The p-type two-dimensional WS2 nanosheet is a single layer, and the WS2 grows laterally to achieve a large size. There are W vacancies in the WS2, which introduce acceptor energy levels and make the two-dimensional WS2 exhibit p-type conductive properties.

9. An application of the high-mobility p-type two-dimensional WS2 according to claim 8, characterized in that: Used to prepare p-type field-effect transistors.

10. The use of the high-mobility p-type two-dimensional WS2 according to claim 9, characterized in that: The hole mobility of the p-type field-effect transistor prepared with two-dimensional WS2 as the active layer is as high as 46.87 cm 2 V -1 s -1 , the on / off ratio is 10 5 , showing excellent p-type field-effect transistor characteristics.

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