A preparation method of MOCVD pulsed growth tungsten selenide film

Abstract

The present invention discloses a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by MOCVD pulsed temperature-variable aging growth, comprising 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 depositing a WSe2 thin film on the sapphire by MOCVD pulsed temperature-variable aging growth using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors; annealing the WSe2 thin film grown on the sapphire to obtain a continuous, large-area, high-quality finished product. The film 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°C to 60°C / hour during the annealing process. The advantages are that the precursors all use gas sources, avoiding carbon contamination of the powder. The high-temperature aging pulsed growth method is used for the first time, effectively controlling the nucleation density, inhibiting secondary layer growth, and promoting WSe2 epitaxial growth. After 6-8 cycles, a continuous, large-area WSe2 film with high electrical properties and controllable growth can be obtained, which has important application prospects in the field of microelectronics.

Description

Technical Field

[0001] The invention relates to a preparation method of a two-dimensional semiconductor tungsten selenide (WSe2) thin film grown by MOCVD pulsed variable temperature aging, belonging to the technical field of semiconductor materials. Background Art

[0002] Two-dimensional transition metal dichalcogenides (TMDs) are atomically thin semiconductor layered materials. Monolayer TMDs have sparked a wave of research due to their unique optoelectronic properties. Common methods for preparing TMDs include mechanical exfoliation, lithium-ion intercalation, chemical vapor deposition, and metal-organic chemical vapor deposition (MOCVD). MOCVD offers a simple structure, good uniformity, in-situ monitoring, and precise control of growth parameters. Its high growth rate facilitates the production of large-scale, wafer-sized thin films, making it promising for widespread industrial application. Currently, MOCVD is primarily used to grow III-V materials, while reports on the growth of TMDs are limited. Therefore, exploring the mechanism and parameters of MOCVD growth of TMDs is of great significance.

[0003] We employed a multi-step, temperature-variable aging pulsed growth method to grow wafer-scale monolayer WSe2 films via a custom-made showerhead cold-wall MOCVD process. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, WSe2 films were synthesized on sapphire via MOCVD pulsed temperature-variable aging, which included periodic interruptions in the precursor supply to suppress secondary nucleation. High-temperature aging also reduced the nucleation density, resulting in larger crystal domains and minimal Se vacancies, thereby improving the crystallinity of TMDs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by MOCVD pulsed temperature-variable aging. The WSe2 thin film prepared by the method has high crystalline quality, large size, excellent electrical properties, and achieves controllable growth. The method is characterized by comprising the following steps:

[0005] Step 1: Clean the c-plane sapphire substrate;

[0006] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0007] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0008] 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.

[0009] 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.

[0010] In step 2, the specific process for growing large-area 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 H2 or Ar atmosphere. High temperatures expose the steps of the sapphire substrate more easily, thereby promoting WSe2 epitaxial growth. After pretreatment, the temperature is lowered to 750-850°C. The precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced into the nucleation chamber under the action of a carrier gas (H2 or Ar) at flow rates of 1 × 10 −3 —2 × 10 −3 The process uses a flow rate of 5-10 sccm and a nucleation time of 10-60 s. The temperature is then raised for high-temperature aging at 800-1000°C for 8-12 minutes. During the aging process, W(CO)6 is stopped, while H2Se flows into the reactor at a constant rate to allow surface diffusion. After the aging phase, W(CO)6 is reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging phase. Six to eight cycles of growth and aging form a high-quality, continuous film. Cooling to 200-300°C under H2Se flow prevents WSe2 decomposition.

[0011] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0012] In the above-mentioned step 2, the advantages of MOCVD equipment are as follows: The graphite turntable in MOCVD 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 beneficial to reduce a series of side reactions at high temperatures and prevent the film from being contaminated. The air inlet of the precursor adopts a shower head design, which is beneficial to control the precursor to fall more evenly on the substrate. The growth of large-area continuous thin films using the MOCVD method has a certain degree of controllability.

[0013] 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 mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C. 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.

[0014] Compared with the prior art, the advantages of the present invention are:

[0015] The precursors are all gas-based, avoiding carbon contamination of the powder. A pulsed growth method with high-temperature aging is employed for the first time, effectively controlling the nucleation density, inhibiting secondary layer growth, and promoting epitaxial WSe2 growth. After 6-8 cycles, continuous, large-area WSe2 films with high electrical properties and controllable growth are obtained, showing promising applications in microelectronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural diagram of the reaction chamber in Example 2.

[0017] Figure 2 These are SEM images of the WSe2 film in Example 2 at different aging temperatures.

[0018] Figure 3 This is a light microscopy image of the film in Example 2. DETAILED DESCRIPTION

[0019] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0020] Example 1:

[0021] This embodiment proposes a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by pulsed MOCVD temperature-variable aging growth, which includes the following steps:

[0022] Step 1: Clean the c-plane sapphire substrate;

[0023] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0024] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0025] 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.

[0026] 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 min.

[0027] In step 2, the specific process of using MOCVD to grow a large-area continuous thin film is as follows: Place the sapphire substrate in the MOCVD growth chamber. First, raise the temperature to 1050°C and perform a high-temperature pretreatment on the sapphire substrate for 1 hour in a H2 atmosphere. At high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2. After pretreatment, the temperature is lowered to 800°C. Under the action of carrier gas H2, the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 30 seconds, with flow rates of 1.5 × 10 −3 The process was repeated with a flow rate of 1 sccm and 7 sccm, followed by a high-temperature aging at 800°C for 10 minutes. During the aging process, W(CO)6 was stopped, while H2Se flowed into the reactor at a constant rate to allow for surface diffusion. After the aging phase, W(CO)6 was reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging. Eight cycles of growth and aging resulted in a high-quality, continuous film. Cooling to 200°C under H2Se flow prevented WSe2 decomposition.

[0028] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0029] In step 3, when the temperature drops below 200°C, the introduction of H2Se and the metal source is stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C, with a ramp rate of 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.

[0030] Example 2:

[0031] This embodiment proposes a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by pulsed MOCVD temperature-variable aging growth, which includes the following steps:

[0032] Step 1: Clean the c-plane sapphire substrate;

[0033] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0034] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0035] 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.

[0036] 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 min.

[0037] In step 2, the specific process of using MOCVD to grow a large-area continuous thin film is as follows: Place the sapphire substrate in the MOCVD growth chamber. First, raise the temperature to 1050°C and perform a high-temperature pretreatment on the sapphire substrate for 1 hour in a H2 atmosphere. At high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2. After pretreatment, the temperature is lowered to 800°C. Under the action of carrier gas H2, the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 30 seconds, with flow rates of 1.5 × 10 −3The process was repeated with a flow rate of 1 sccm and 7 sccm, followed by a high-temperature aging at 900°C for 10 minutes. During the aging process, W(CO)6 was stopped, while H2Se flowed into the reactor at a constant rate to allow for surface diffusion. After the aging phase, W(CO)6 was reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging. Eight cycles of growth and aging resulted in a high-quality, continuous film. Cooling to 200°C under H2Se flow prevented WSe2 decomposition.

[0038] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0039] In step 3, when the temperature drops below 200°C, the introduction of H2Se and the metal source is stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C, with a ramp rate of 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.

[0040] Example 3:

[0041] This embodiment proposes a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by pulsed MOCVD temperature-variable aging growth, which includes the following steps:

[0042] Step 1: Clean the c-plane sapphire substrate;

[0043] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0044] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0045] 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.

[0046] 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 min.

[0047] In step 2, the specific process of using MOCVD to grow a large-area continuous thin film is as follows: Place the sapphire substrate in the MOCVD growth chamber. First, raise the temperature to 1050°C and perform a high-temperature pretreatment on the sapphire substrate for 1 hour in a H2 atmosphere. At high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2. After pretreatment, the temperature is lowered to 800°C. Under the action of carrier gas H2, the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 30 seconds, with flow rates of 1.5 × 10 −3 The process was repeated with a flow rate of 1 sccm and 7 sccm, followed by a high-temperature aging at 1000°C for 10 minutes. During the aging process, W(CO)6 was stopped, while H2Se flowed into the reactor at a constant rate to allow for surface diffusion. After the aging phase, W(CO)6 was reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging. Eight cycles of growth and aging resulted in a high-quality, continuous film. Cooling to 200°C under H2Se flow prevented WSe2 decomposition.

[0048] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0049] In step 3, when the temperature drops below 200°C, the introduction of H2Se and the metal source is stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C, with a ramp rate of 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.

[0050] Example 4:

[0051] This embodiment proposes a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by pulsed MOCVD temperature-variable aging growth, which includes the following steps:

[0052] Step 1: Clean the c-plane sapphire substrate;

[0053] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0054] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0055] 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.

[0056] 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 min.

[0057] In step 2, the specific process of using MOCVD to grow a large-area continuous thin film is as follows: Place the sapphire substrate in the MOCVD growth chamber. First, raise the temperature to 1050°C and perform a high-temperature pretreatment on the sapphire substrate for 1 hour in a H2 atmosphere. At high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2. After pretreatment, the temperature is lowered to 800°C. Under the action of carrier gas H2, the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 30 seconds, with flow rates of 1.5 × 10 −3 The process was repeated with a flow rate of 1 sccm and 7 sccm, followed by a high-temperature aging at 1100°C for 10 minutes. During the aging process, W(CO)6 was stopped, while H2Se flowed into the reactor at a constant rate to allow for surface diffusion. After the aging phase, W(CO)6 was reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging. Eight cycles of growth and aging resulted in a high-quality, continuous film. Cooling to 200°C under H2Se flow prevented WSe2 decomposition.

[0058] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0059] In step 3, when the temperature drops below 200°C, the introduction of H2Se and the metal source is stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C, with a ramp rate of 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.

[0060] Embodiment 5:

[0061] This embodiment proposes a method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by pulsed MOCVD temperature-variable aging growth, which includes the following steps:

[0062] Step 1: Clean the c-plane sapphire substrate;

[0063] Step 2: Place the cleaned substrate into the MOCVD reaction chamber and perform high-temperature pretreatment on the substrate. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire.

[0064] Step 3: Annealing the WSe2 film grown on sapphire yields a continuous, large-area, high-quality finished product. Annealing is performed in a mixture of hydrogen (H2) and argon (Ar) at 200°C to 400°C for 2-3 hours, with a ramp rate of 40°C to 60°C per hour.

[0065] 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.

[0066] 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 min.

[0067] In step 2, the specific process of using the MOCVD method to grow a large-area continuous thin film is as follows: Place the sapphire substrate in the MOCVD growth chamber. First, raise the temperature to 1050°C and perform a high-temperature pretreatment on the sapphire substrate for 1 hour in an Ar atmosphere. At high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2. After pretreatment, the temperature is lowered to 800°C. Under the action of the carrier gas Ar, the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 30 seconds, with flow rates of 1.5 × 10 −3sccm and 7 sccm, followed by high-temperature aging at 1000°C for 10 minutes. During the aging process, W(CO)6 was stopped, while H2Se flowed into the reactor at a constant rate to allow surface diffusion. After the aging phase, W(CO)6 was reintroduced into the reactor at half the flow rate (compared to the nucleation phase) to grow WSe2, followed by another high-temperature aging. Eight cycles of growth and aging formed a high-quality, continuous film. Cooling to 200°C under H2Se flow prevented WSe2 decomposition.

[0068] Here, high-temperature aging inhibits high-density nucleation and second-layer growth, promoting the formation of larger crystal domains and minimal Se vacancies, which is beneficial for epitaxial growth. The number of cycles required to form a continuous film is determined by the amount of precursor introduced.

[0069] In step 3, when the temperature drops below 200°C, the introduction of H2Se and the metal source is stopped. The film is annealed in a mixture of H2 and Ar in the reaction chamber at a temperature of 200°C to 400°C, with a ramp rate of 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.

[0070] 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 higher quality of thin film crystallization. Figure 2 The SEM images of WSe2 at different aging temperatures in Example 2 are shown. The high-temperature aging method effectively promotes the expansion of the crystal domain and inhibits the growth of the second layer. Figure 3 This is a light microscopy image of the WSe2 film in Example 2. It can be seen that the film is continuous and uniform.

Claims

1. A method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by MOCVD pulsed temperature-variable aging growth, 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. Using tungsten hexacarbonyl (W(CO)6) and hydrogen selenide (H2Se) as precursors, MOCVD pulsed temperature-variable aging growth is used to deposit WSe2 thin film on sapphire. 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 MOCVD pulsed temperature-variable aging growth 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 pulsed MOCVD temperature-variable aging growth according to claim 1, characterized in that In step 2, the specific process of growing a large-area continuous thin film using the MOCVD method is as follows: placing a sapphire substrate in 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 a treatment atmosphere of H2 or Ar; at high temperatures, the steps of the sapphire substrate are more easily exposed, thereby promoting the epitaxial growth of WSe2; after pretreatment, the temperature is lowered to 750-850°C, and under the action of a carrier gas (H2 or Ar), the precursors hexacarbonyl tungsten (W(CO)6) and hydrogen selenide (H2Se) are introduced for nucleation for 10s-60s, with flow rates of 1 × 10 −3 —2 × 10 −3 sccm and 5-10 sccm, and then the temperature is raised for high-temperature aging for 8-12 min (800 ℃-1100 ℃); during the aging process, W(CO)6 is stopped, and H2Se flows into the reactor at a constant rate to allow surface diffusion; after the aging stage, W(CO)6 is reintroduced into the reactor at half the flow rate (compared to the nucleation stage) to grow WSe2, and then high-temperature aging is carried out again; high-quality continuous films can be formed after 6-8 cycles of growth and aging; the temperature is cooled to 200 ℃-300 °C under the flow of H2Se to avoid decomposition of WSe2.

4. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by MOCVD pulsed temperature-variable aging growth according to claim 3, characterized in that The high temperature aging inhibits high-density nucleation and two-layer growth, promotes the formation of larger crystal domains and minimal Se vacancies, and is beneficial to epitaxial growth; the number of cycles to form a continuous film is determined by the amount of precursor introduced.

5. The method for preparing a two-dimensional semiconductor tungsten selenide (WSe2) thin film by MOCVD pulsed temperature-variable aging growth according to claim 1, characterized in that In 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 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 carbon contamination of the sample by the precursors; the 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 precursor air inlet adopts a shower head design, which is conducive to controlling the precursor to fall more evenly on the substrate.

Images