A preparation method for MOCVD continuous growth of tungsten selenide thin film

Abstract

The present invention discloses a preparation method of a two-dimensional semiconductor tungsten selenide (WSe2) thin film grown by MOCVD continuous growth, which comprises the following steps: cleaning a c-plane sapphire substrate; placing the cleaned substrate into an MOCVD reaction chamber, performing high-temperature pretreatment on the substrate, and then using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors to deposit a WSe2 thin film on the sapphire by MOCVD continuous growth; annealing the WSe2 thin film grown on the sapphire to obtain a continuous, large-area, and high-crystalline quality finished product. The film annealing is carried out in a mixed atmosphere of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2 to 3 hours, with a heating and cooling rate of 40 to 60°C / h during the annealing process; the advantage is that the precursors all use gas sources, avoiding carbon contamination of the powder; after 60 min-100 min, a continuous, large-area, high-electrical-performance, and controllable-growth WSe2 thin film can be obtained, which has important application prospects in the field of microelectronics.

Description

Technical Field

[0001] The invention relates to a preparation method for a two-dimensional semiconductor tungsten selenide (WSe2) thin film grown by MOCVD continuous growth. Background Art

[0002] Layered two-dimensional transition metal dichalcogenides (TMDs) have become an important foundational electronic material for continuing Moore's Law for integrated circuits due to their unique electrical and optical properties, triggering a wave of research in next-generation nanoelectronic and optoelectronic devices. To obtain high-quality wafer-scale monolayers of two-dimensional TMDs, numerous researchers have attempted a variety of methods, including mechanical exfoliation of bulk TMD crystals, liquid-phase exfoliation, chemical vapor deposition (CVD), and metal-organic chemical vapor deposition (MOCVD). Compared with CVD, MOCVD allows for precise control of growth parameters and precursor supply, resulting in the growth of wafer-scale thin films. This controllable deposition method is more suitable for scalable production of two-dimensional materials for industrial applications. Therefore, exploring the MOCVD growth mechanism and controlling key parameters are of great significance for obtaining high-quality monolayer TMD films.

[0003] To date, previous MOCVD methods for growing thin films have had some significant drawbacks, such as small crystal domain size (typically a few hundred nanometers); the use of carbon-containing MO precursors in some MOCVD growth processes, such as (CH3)2X or (C2H5)2X, (X=S, Se), which inevitably leads to the deposition of carbon particles on the TMDs surface; in addition, the use of higher growth temperatures reduces the nucleation density, but also increases the desorption of Se atoms, leading to the formation of Se vacancies, thereby reducing the crystallization quality.

[0004] We grew wafer-scale monolayer WSe2 thin films using a custom-made showerhead cold-wall MOCVD process. Tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) source gases were used as precursors to avoid carbon contamination. WSe2 films were synthesized on sapphire using a three-step MOCVD growth process (nucleation, maturation, and growth). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for continuously growing high-quality two-dimensional semiconductor thin films (WSe2) using MOCVD. The WSe2 thin films produced by the method have high crystalline quality, large size, excellent electrical properties, and controllable growth. The method is characterized by comprising the following steps:

[0006] Step 1: Clean the c-plane sapphire substrate;

[0007] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0008] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a hydrogen (H2) and argon (Ar) atmosphere at 200°C to 400°C for 2-3 hours, with a ramp rate of 40-60°C / hour.

[0009] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0010] The sapphire substrate has a CM plane of 0.2°-4° and a CA plane of 0.2°-4°. The parameters of room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 10-15 sccm, and time 10 min.

[0011] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1000-1050°C, and the sapphire substrate is pretreated for 0.5-2 hours in an atmosphere of H₂ or Ar₂. High-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe₂ epitaxial growth. After substrate pretreatment, the temperature is lowered to 750-850°C, and the nucleation, maturation, and growth steps are performed. H₂ or Ar₂ is used as the carrier gas throughout the entire growth process.

[0012] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation takes 10 to 60 seconds, aging for 8 to 12 minutes, and growth for 60 to 100 minutes, ultimately forming a high-quality, continuous monolayer film. While H2Se is being introduced, the film is cooled to 200 to 300 °C to prevent WSe2 decomposition.

[0013] In the step 2, the advantages of the MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0014] In step 3, when the temperature drops below 200°C to 300°C, the H2Se and metal source are stopped. The film is annealed in a H2 and Ar atmosphere in the reaction chamber. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] All precursors are sourced from gases, avoiding carbon contamination. A graphite turntable and custom-made showerhead-style inlet facilitate uniform film growth. A cold wall design minimizes side reactions at high temperatures. For the first time, a three-step, continuous growth process (nucleation, maturation, and growth) using self-assembled MOCVD was employed to synthesize WSe2 thin films on sapphire. This method allows for controlled growth, effectively controlling nucleation density, suppressing secondary layer growth, and promoting epitaxial WSe2 growth. The result is a continuous, large-area WSe2 film with high electrical properties and controllable growth, offering promising applications in microelectronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of the reaction chamber in Example 2.

[0018] Figure 2 These are SEM images of the WSe2 film nucleation, ripening, and growth stages in Example 2.

[0019] Figure 3 This is the AFM image of the WSe2 film in Example 2. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0021] Example 1:

[0022] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0023] Step 1: Clean the c-plane sapphire substrate;

[0024] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0025] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 400°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a heating rate of 40°C / hour.

[0026] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0027] The sapphire substrate has a CM surface of 0.2°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 minutes.

[0028] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 0.5 hours in an H2 atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe2 epitaxial growth. After substrate pretreatment, the temperature is lowered to 800°C for the three steps of nucleation, maturation, and growth. H2 is used as the carrier gas throughout the entire growth process.

[0029] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0030] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0031] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 400°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0032] Example 2:

[0033] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0034] Step 1: Clean the c-plane sapphire substrate;

[0035] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0036] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 400°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a heating rate of 40°C / hour.

[0037] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0038] The sapphire substrate has a CM surface of 0.2°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 minutes.

[0039] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 0.5 hours in an Ar atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe2 epitaxial growth. After substrate pretreatment, the temperature is lowered to 800°C for the nucleation, maturation, and growth steps. Ar is used as the carrier gas throughout the entire growth process.

[0040] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0041] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0042] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 400°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0043] Example 3:

[0044] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0045] Step 1: Clean the c-plane sapphire substrate;

[0046] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0047] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 400°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a heating rate of 40°C / hour.

[0048] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0049] The sapphire substrate has a CM plane of 0.5°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 minutes.

[0050] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 0.5 hours in an Ar atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe2 epitaxial growth. After substrate pretreatment, the temperature is lowered to 800°C for the nucleation, maturation, and growth steps. Ar is used as the carrier gas throughout the entire growth process.

[0051] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0052] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0053] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 400°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0054] Example 4:

[0055] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0056] Step 1: Clean the c-plane sapphire substrate;

[0057] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0058] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 300°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a ramp rate of 40°C / hour.

[0059] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0060] The sapphire substrate has a CM surface of 4°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 minutes.

[0061] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 0.5 hours in an Ar atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe2 epitaxial growth. After substrate pretreatment, the temperature is lowered to 800°C for the nucleation, maturation, and growth steps. Ar is used as the carrier gas throughout the entire growth process.

[0062] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0063] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0064] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 300°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0065] Embodiment 5:

[0066] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0067] Step 1: Clean the c-plane sapphire substrate;

[0068] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0069] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 300°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a ramp rate of 40°C / hour.

[0070] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0071] The sapphire substrate has a CA plane of 0.2°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 minutes.

[0072] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 0.5 hours in an Ar atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting WSe2 epitaxial growth. After substrate pretreatment, the temperature is lowered to 800°C for the nucleation, maturation, and growth steps. Ar is used as the carrier gas throughout the entire growth process.

[0073] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0074] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0075] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 300°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0076] Example 6:

[0077] This embodiment proposes a method for continuously growing a high-quality two-dimensional semiconductor thin film (WSe2) using MOCVD, which includes the following steps:

[0078] Step 1: Clean the c-plane sapphire substrate;

[0079] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors.

[0080] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed at 300°C for two hours in a mixture of hydrogen (H2) and argon (Ar) at a ramp rate of 40°C / hour.

[0081] The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

[0082] The sapphire substrate has a CA plane of 4°, and the parameters of the room temperature ultrasound and plasma setting are: power 100W, oxygen flow rate 15 sccm, and time 10 min.

[0083] In step 2, the specific process for growing large, continuous thin films using MOCVD is as follows: A sapphire substrate is placed in an MOCVD growth chamber. The temperature is first raised to 1050°C and pretreated for 2 hours in an Ar atmosphere. This high-temperature pretreatment helps expose the steps on the sapphire substrate, thereby promoting epitaxial growth of WSe2. After substrate pretreatment, the temperature is lowered to 800°C for the three steps of nucleation, maturation, and growth. Ar is used as the carrier gas throughout the entire growth process.

[0084] Here, using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 nucleation took 30 seconds, aging for 10 minutes, and growth for 60 minutes, ultimately forming a high-quality, continuous monolayer film. The temperature was then cooled to 200°C while H2Se was introduced to prevent WSe2 decomposition.

[0085] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: the sapphire substrate is placed on a graphite disk in the MOCVD growth chamber. The graphite turntable is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2. All precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor. MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

[0086] In step 3, when the temperature drops below 200°C, the H2Se and metal source are stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber. The annealing temperature is 300°C, and the heating and cooling rate during the annealing process is 40°C / hour. After annealing, the film is cooled to room temperature and purged with nitrogen. The WSe2 film is placed in a nitrogen-purged glove box to avoid exposure and minimize further sample degradation.

[0087] Figure 1 The structure diagram of the reaction chamber in Example 2. The self-assembled MOCVD equipment adopts a cold wall and shower head design, which is conducive to obtaining a continuous and uniform single-layer film with high crystal quality. Figure 2 These are SEM images of the WSe2 nucleation, ripening and growth stages in Example 2. Figure 3 This is an AFM image of WSe2 in Example 2. It can be seen from the image that the thickness of WSe2 is 0.8 nm, which is a single layer.

Claims

1. A method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD, characterized in that The following steps are involved: Step 1: Clean the c-plane sapphire substrate; Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Then, WSe2 thin film is deposited on sapphire by continuous MOCVD growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors. Step 3: Annealing the WSe2 film grown on sapphire to obtain a continuous, large-area, high-quality finished product; annealing is performed in a mixed atmosphere of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2 to 3 hours, with a heating and cooling rate of 40 to 60°C per hour.

2. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD according to claim 1, characterized in that The specific process of step 1 is as follows: immersing the sapphire substrate in acetone, ultrasonically treating it for 10 minutes, then immersing it in isopropanol and ultrasonically treating it for 10 minutes, and then immersing it in ethanol and ultrasonically treating it for 10 minutes. After taking it out, it is blown dry with a nitrogen gun and finally cleaned with an oxygen plasma machine for 10 minutes.

3. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD according to claim 2, characterized in that The sapphire substrate has a CM plane of 0.2°-4° and a CA plane of 0.2°-4°. The parameters of the room temperature ultrasound plasma setting are: power 100 W, oxygen flow rate 10-15 sccm, and time 10 minutes.

4. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD according to claim 1, characterized in that In the step 2, the specific process of using the MOCVD method to grow a large-area continuous single-layer film is as follows: placing a sapphire substrate into an MOCVD growth chamber; first raising the temperature to 1000-1050°C, and performing a high-temperature pretreatment on the sapphire substrate for 0.5h-2h in an atmosphere of H2 or Ar; at high temperature, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2; after pretreatment, the temperature is lowered to 750°C-850°C, and the nucleation, aging, and growth steps are performed; during the entire growth process, the carrier gas is H2 or Ar; the precursors are tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se), WSe2 nucleation takes 10 s-60 s, aging takes 8-12 min, and growth takes 60-100 min, and finally a high-quality continuous single-layer film can be formed; while H2Se is introduced, the temperature is cooled to 200°C-300°C to avoid decomposition of WSe2.

5. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD according to claim 1, characterized in that In the above-mentioned step 2, the advantages of the MOCVD equipment are as follows: the graphite turntable on which the sapphire substrate is placed is driven by a spin motor and can rotate at a constant speed during the growth process to promote the uniform nucleation of WSe2; all precursors use gas sources, including tungsten hexacarbonyl (W(CO)6), hydrogen selenide (H2Se), H2 and Ar, which can greatly reduce the carbon contamination of the sample by the precursor; MOCVD adopts a cold wall design, which is conducive to reducing a series of side reactions at high temperatures and preventing the film from being contaminated; the air inlet of the precursor adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

6. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by continuous growth of MOCVD according to claim 1, characterized in that In step three, when the temperature drops below 200°C - 300°C, the H2Se and metal source are stopped from being introduced; the film is annealed in a mixed atmosphere of H2 and Ar in the reaction chamber; the annealing temperature is 200°C ~ 400°C, and the heating and cooling rate during the annealing process is 40~60°C / hour; after the annealing is completed, it is cooled to room temperature, taken out and purged with nitrogen; the WSe2 is placed in a nitrogen-purged glove box to avoid exposure and reduce further sample degradation.

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