Novel vapor phase epitaxial growth method of high-quality WSe2 single crystal film

Abstract

The invention provides a novel vapor phase epitaxial growth method of a high-quality WSe2 single crystal film, and relates to the technical field of semiconductor material science and micro-nano manufacturing engineering, and the method comprises the four steps of substrate pretreatment, precursor loading, temperature field and vacuum establishment and single crystal film growth. According to the preparation method, an improved vapor phase epitaxy process is adopted, the preparation of the large-area and high-uniformity WSe2 single crystal film is realized through precise regulation and control on source material supply, temperature field distribution, atmosphere control and substrate selection, and the preparation of the large-area and high-uniformity WSe2 single crystal film is realized by remarkably improving the crystal integrity and thickness uniformity of the WSe2 film. The core problems that the two-dimensional material is prone to generating polycrystal and inclusion defects, the number of layers is uncontrollable and the like in epitaxial preparation are effectively solved, and the applicability of the two-dimensional material in large-scale chip manufacturing is enhanced. And meanwhile, the method has good repeatability and process compatibility, can be adapted to various substrates such as silicon substrates, sapphire and quartz, and has the potential of being popularized as an industrial-grade standard process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor material science and micro-nano manufacturing engineering, and particularly relates to a novel vapor phase epitaxy growth method of a high-quality WSe2 single crystal thin film. BACKGROUND

[0002] In recent years, as a typical two-dimensional material, tungsten diselenide (WSe2) has made remarkable progress in the research and application in the fields of transistors, photodetectors and flexible electronic devices due to its excellent layered structure, adjustable band gap, high stability and high electron mobility. WSe2 belongs to the family of transition metal dichalcogenides (TMDs), and this kind of material has rich electronic properties, including high carrier mobility, adjustable band gap and excellent optical properties. Due to its excellent performance, WSe2 has been widely used in many fields such as novel transistors, photodetectors, gas sensors, solar cells, flexible displays and optoelectronic devices.

[0003] Due to its layered structure, WSe2 can still maintain good semiconductor properties in a very thin state of a few layers (even a single layer) and exhibit excellent electrical and optical properties. However, although WSe2 has great application potential in various electronic devices, the defect problem, grain size problem and thickness uniformity problem in the growth process have become major challenges to improve its performance in devices.

[0004] Existing WSe2 thin film growth technologies mainly include mechanical exfoliation, liquid phase epitaxy and vapor phase epitaxy. Among them, the vapor phase epitaxy method (CVD method) is the most commonly used preparation method because it can realize efficient growth of large-area thin films. However, the existing vapor phase epitaxy method still has some problems, for example: in the process of growing WSe2 thin films by the current vapor phase epitaxy method, it is often difficult to obtain a single crystal thin film with stable quality due to uneven source supply or uneven temperature field distribution; at the same time, in the traditional CVD method, due to inaccurate temperature control and uneven source distribution, a large number of defects are often generated on the surface of the thin film. These defects may be vacancies, grain boundaries or the introduction of other impurities, which will have a negative impact on the electronic properties of the WSe2 thin film; due to the unevenness of the reaction atmosphere and the temperature field distribution, the WSe2 thin film grown by the traditional CVD method often shows obvious thickness non-uniformity, especially when grown on a large-area substrate, the thickness of the thin film is often difficult to keep consistent, therefore, the application proposes a novel vapor phase epitaxy growth method of a high-quality WSe2 single crystal thin film to solve the problems existing in the prior art. SUMMARY

[0005] In view of the above problems, the present application aims to provide a novel vapor phase epitaxy growth method of high-quality WSe2 single crystal thin film, which has the advantages of improving the quality of the thin film and reducing defects and unevenness in the growth process, and can solve the problems in the prior art.

[0006] To achieve the object of the present application, the present application realizes the following technical scheme: a novel vapor phase epitaxy growth method of high-quality WSe2 single crystal thin film, comprising the following steps:

[0007] Step one, pretreatment of the substrate

[0008] One of silicon-based, sapphire, and quartz glass is selected as the target substrate, and then the substrate is sequentially immersed in acetone, anhydrous ethanol, and deionized water, each for ultrasonic cleaning for 10 min, and then dried with nitrogen, and then placed in a plasma cleaning machine and subjected to plasma treatment in an argon-oxygen mixed gas atmosphere, and then installed in a CVD reaction chamber;

[0009] Step two, precursor loading

[0010] Tungsten powder and selenium powder are loaded into graphite boat A and graphite boat B in the CVD reaction chamber at a molar ratio of 1:8 to 1:12, and then mixed gas is introduced into the reaction chamber through a double-path mass flowmeter device;

[0011] Step three, establishment of a temperature field and vacuum

[0012] After loading is completed, the reaction chamber is evacuated to a base vacuum of <5x10 -4 Pa, and then the substrate is heated to a temperature of 750-850℃;

[0013] Step four, single crystal thin film growth

[0014] In the initial nucleation stage, the mixed gas is again introduced for 5 min, and then the precursor is heated, graphite boat A and graphite boat B are respectively raised to a preset temperature at a rate of 5℃ / min, the heating power of graphite boat B is dynamically adjusted to maintain a selenium-tungsten vapor ratio of 2.1-2.2:1, and then the temperature is maintained in the lateral epitaxy stage, and the mixed gas flow is reduced to 100-150sccm to enable long-range migration of adsorbed atoms to grow epitaxially along the crystal nucleus edge to form a single crystal thin film with a thickness of 1-3nm, the precursor heating is turned off, and the growth is stopped;

[0015] Step five, post-treatment and collection

[0016] The precursor heating is turned off, the mixed gas flow is increased to 200sccm, the reaction chamber is purged for 10 min, and then the sample is taken out after slow cooling to room temperature at a rate of 1-3℃ / min.

[0017] Further improvement lies in that: in the step one, the plasma processing parameters are adjusted according to the substrate material, and the specific adjustment is as follows:

[0018] When the substrate is silicon-based, the argon-oxygen volume ratio is 3:1, the power is 50W, and the processing time is 5min;

[0019] When the substrate is sapphire, the argon-oxygen volume ratio is 2:1, the power is 40W, and the processing time is 3min;

[0020] When the substrate is quartz glass, the argon-oxygen volume ratio is 4:1, the power is 60W, and the processing time is 7min.

[0021] Further improvement lies in that: in the step one, after the plasma processing is completed, the water contact angle of the substrate surface is tested by using a contact angle measuring instrument, and the requirements are: silicon-based ≤30°, sapphire ≤40° and quartz glass ≤50°.

[0022] Further improvement lies in that: in the step two, the main path carrier gas of the double-path mass flowmeter device is argon with a purity of ≥99.9995%, and the total flow is 150-200sccm;

[0023] The branch mixed gas of the double-path mass flowmeter device is composed of hydrogen and hydrogen selenide, and the flow is 5%-25% of the total flow.

[0024] Further improvement lies in that: in the step two, the flow ratio of hydrogen selenide in the branch mixed gas is dynamically adjusted, and the adjustment rule is:

[0025] In the initial nucleation stage, the flow ratio of hydrogen selenide is 3%-5%;

[0026] In the lateral epitaxy stage, the flow ratio of hydrogen selenide is reduced to 1%-2%.

[0027] Further improvement lies in that: in the step three, the temperature is raised at a rate of 5-10℃ / min.

[0028] Further improvement lies in that: in the step three, the temperature gradient is compensated by using a partition heating belt, so that the substrate surface temperature uniformity reaches ±1℃.

[0029] Further improvement lies in that: in the step four, the preset temperature corresponding to the tungsten powder is 850-900℃, and the preset temperature corresponding to the selenium powder is 250-300℃.

[0030] The beneficial effects of the present application are: by using the improved vapor phase epitaxy process, the source material supply, temperature field distribution, atmosphere control and substrate selection are accurately controlled, and large-area and high-uniformity WSe2 single crystal thin film preparation is successfully realized. The crystal integrity and thickness uniformity of the WSe2 thin film are effectively improved, and the core problems such as polycrystalline, inclusion defects and uncontrollable layer number of two-dimensional materials in the epitaxial growth process are solved.

[0031] The application has good repeatability and process compatibility, can adapt to various substrates such as silicon, sapphire and quartz, and has the potential to be promoted to an industrial standard process. The successful obtaining of high-quality WSe2 thin films not only provides a solid foundation for the development of new van der Waals heterostructure devices, two-dimensional photonic crystals and reconfigurable electronic platforms, but also lays a foundation for the application of key materials in the field of future new chips. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a step flowchart of the application. DETAILED DESCRIPTION

[0033] In order to deepen the understanding of the application, the application will be further described below in combination with examples, and the examples are only used to explain the application and do not constitute a limitation on the protection scope of the application.

[0034] In the following examples, a vertical tube CVD reaction chamber is involved, which is integrated with a double-zone independent resistance heating system (composed of two parallel graphite heating blocks, the distance between the heating blocks is 150-200 mm, each heating block is provided with a PID temperature controller with an accuracy of ±1℃, and the heating power range is 0-1000W) at the top of the chamber; a gas inlet (diameter φ10-15mm) is provided at the bottom of the chamber and connected to a double-path mass flow meter (MFC) device (main path MFC1 controls the carrier gas, and branch path MFC2 controls the mixed gas); a high-temperature-resistant observation window (with quartz glass) is provided on the side wall of the chamber for observing the source material loading state. The graphite boat is a precursor carrying device in the reaction chamber, graphite boat A and graphite boat B are symmetrically fixed on the heating surface of the double-zone heating block through a high-temperature-resistant graphite support (thickness 2-3mm) (the bottom of the graphite boat is in contact with the surface of the heating block to ensure uniform heat transfer), the two boats are horizontally spaced 5-8mm (aligned through the positioning scale line on the support), and correspond to the horizontal two sides of the center axis of the chamber. Further, the edge of the substrate is aligned with the side edge of the graphite boat A and B (calibrated by the laser positioning instrument outside the chamber), and the center of the substrate is ensured to coincide with the center axis of the chamber (deviation <0.5mm).

[0035] Example 1

[0036] According to Figure 1 , the present embodiment proposes a new vapor phase epitaxy growth method of high-quality WSe2 single crystal thin film, which comprises the following steps:

[0037] Step 1, pretreatment of the substrate

[0038] Silicon is chosen as the target substrate, and then the substrate is sequentially immersed in acetone, anhydrous ethanol and deionized water, each ultrasonic cleaning for 10 min, the cleaning frequency is 40 kHz, the power is 100 W, the purpose of cleaning is to remove organic matter, metal ions and particle contaminants on the surface of the substrate;

[0039] After cleaning, dry with nitrogen (purity ≥ 99.999%) to avoid surface water stains and ensure that the substrate surface is dry and free of contaminants. Then place it in a plasma cleaner and perform plasma treatment in an argon-oxygen mixed gas atmosphere. The main purpose of plasma treatment is to activate the surface hydroxyl (-OH) through sputter etching and enhance the surface energy of the substrate to improve its hydrophilicity. This allows the substrate surface to better promote uniform nucleation of the WSe2 film, thereby improving film quality. Plasma treatment parameters are adjusted according to the substrate material as follows:

[0040] When the substrate is silicon-based, the argon-oxygen volume ratio is 3:1, the power is 50 W, and the treatment time is 5 min;

[0041] By precisely controlling the water contact angle, it can be ensured that the substrate surface has sufficient activity, which is very critical for subsequent epitaxial growth of WSe2. If the water contact angle does not meet the requirements, the plasma treatment parameters (such as increasing the power or extending the treatment time) need to be adjusted according to the actual situation to ensure the quality of the substrate surface.

[0042] After the plasma treatment is completed, the water contact angle of the substrate surface is measured using a contact angle meter, and the requirement is that the silicon-based substrate is ≤ 30°.

[0043] After treatment, install it in the CVD reaction chamber.

[0044] Step two, precursor loading

[0045] Tungsten powder (≥99.999%) and selenium powder are loaded into graphite boat A and graphite boat B in the CVD reaction chamber according to the molar ratio of 1:12 (tungsten powder: selenium powder), and the two graphite boats are symmetrically installed in the top independent heating area of the reaction chamber to ensure uniform heating. Then the mixed gas is introduced into the reaction chamber through the double mass flowmeter device, and the gas flow in the reaction chamber is controlled by the double mass flowmeter device, and the configuration is as follows:

[0046] The main carrier gas is argon with a purity of ≥99.9995%, and the total flow rate is 200 sccm (standard cubic centimeters per minute) to ensure the stability of the reaction atmosphere;

[0047] The branch mixed gas of the double mass flowmeter device is composed of hydrogen (purity ≥ 99.999%) and hydrogen selenide (purity ≥ 99.99%), and the flow rate is 25% of the total flow rate. The flow rate ratio of the mixed gas needs to be dynamically adjusted to optimize the supply of selenium source during the reaction process.

[0048] Further, the flow ratio of hydrogen selenide in the branch mixed gas should be dynamically adjusted at different epitaxial growth stages, and the adjustment rule is:

[0049] In the initial nucleation stage (0-10 min), the flow ratio of hydrogen selenide is 5%, to ensure uniform nucleation of crystal nucleus and preliminary growth of thin film;

[0050] In the lateral epitaxial stage (10-60 min), the flow ratio of hydrogen selenide is reduced to 2% to avoid excessive supply of selenium source, thereby controlling the thickness and growth rate of the epitaxial film.

[0051] Step three, temperature field and vacuum establishment

[0052] After loading, use a high-efficiency vacuum pump to pump the reaction chamber to a background vacuum of <5x10 -4 Pa, to ensure that the vacuum environment in the reaction chamber can effectively remove residual gas and impurities, thereby providing a stable atmosphere for the subsequent growth process.

[0053] Then heat the substrate, increase the temperature at a rate of 10℃ / min to avoid thermal stress cracking or uneven growth of the substrate caused by sudden temperature rise, and then raise the substrate temperature to 850℃.

[0054] At the same time, compensate the temperature gradient by using a partition heating belt to make the substrate surface temperature uniformity reach ±1℃. Specifically, an annular auxiliary heating belt (width 5-10mm, power 50-200W adjustable) is added below the double-zone graphite heating block, which surrounds the substrate (distance from the substrate edge 10-15mm). The PID controller collects real-time substrate temperature data (infrared thermometer feedback), and if the edge area temperature is higher than the center by >1℃, the power of the annular heating belt is reduced;

[0055] If it is lower, the power is increased, and finally the substrate surface temperature uniformity reaches ±1℃. This control can effectively avoid uneven film growth caused by uneven temperature, and ensure the quality of the WSe2 film.

[0056] Step four, single crystal thin film growth

[0057] In the initial nucleation stage, the mixed gas is again introduced for 5min, and then the precursor is heated, so that graphite boat A and graphite boat B are respectively increased to the preset temperature at a rate of 5℃ / min. The preset temperature of tungsten powder is 900℃, and the preset temperature of selenium powder is 300℃.

[0058] During the heating process, the heating power of graphite boat B is dynamically adjusted to maintain the selenium-tungsten vapor ratio at 2.2:1, which is slightly higher than the stoichiometric ratio of 2:1 (the stoichiometric ratio of WSe2 is tungsten:selenium = 1:2, which corresponds to a selenium-tungsten vapor ratio of 2:1), to avoid excessive or insufficient tungsten source, which can cause element imbalance in the film and affect the crystalline quality of the film.

[0059] Then, the temperature (substrate temperature and temperature inside graphite boat A and graphite boat B) is maintained during the lateral epitaxial stage, and the mixed gas flow is reduced to 150 sccm to reduce the gas concentration in the reaction atmosphere and avoid excessive gas from triggering unnecessary reactions. Then, under the condition of low gas flow, the thin film of WSe2 grows by long-range migration of adsorbed atoms along the edge of the crystal nucleus. This process can effectively control the uniformity and crystal structure of the film, forming a single-crystal thin film with a thickness of 3 nm (corresponding to 3 layers). The precursor heating is turned off, and the growth is stopped.

[0060] In this step, the gas is introduced in step two, vacuum is pumped in step three, and the gas is introduced again in step four. The "fill-pump-fill" cycle achieves exponential improvement in gas purity, avoiding the drawbacks of "single large flow purging" (such as gas flow disturbance causing precursor vapor flow field disorder)

[0061] Step five, post-processing and collection

[0062] The precursor heating is turned off, the mixed gas flow is increased to 200 sccm, the reaction chamber is purged for 10 min, and then the temperature is slowly cooled to room temperature (25±2℃) at a rate of 3℃ / min. The sample is removed.

[0063] Example two

[0064] According to Figure 1 As shown in the figure, the present embodiment proposes a new vapor phase epitaxial growth method for high-quality WSe2 single-crystal thin film, which includes the following steps:

[0065] Step one, pretreatment of the substrate

[0066] Blue sapphire is selected as the target substrate, and then the substrate is sequentially immersed in acetone, anhydrous ethanol and deionized water, each for ultrasonic cleaning for 10 min, with a cleaning frequency of 40 kHz and a power of 100 W. After cleaning, the substrate is dried with nitrogen (purity ≥ 99.999%). Then, the substrate is placed in a plasma cleaning machine and subjected to plasma treatment in an argon-oxygen mixed gas atmosphere. The plasma treatment parameters are adjusted according to the substrate material, as follows:

[0067] When the substrate is blue sapphire, the argon-oxygen volume ratio is 2:1, the power is 40 W, and the treatment time is 3 min.

[0068] After the plasma treatment is completed, the water contact angle of the substrate surface is measured using a contact angle measuring instrument. The requirement is that the blue sapphire is ≤40°.

[0069] After the process is completed, it is installed in the CVD reaction chamber.

[0070] Step two, precursor loading

[0071] Tungsten powder (≥99.999%) and selenium powder are loaded into graphite boat A and graphite boat B in the CVD reaction chamber in a molar ratio of 1:8 (tungsten powder: selenium powder), and the two graphite boats are symmetrically installed in the independent heating area at the top of the reaction chamber to ensure uniform heating. Then the mixed gas is introduced into the reaction chamber through the double mass flowmeter device, and the gas flow in the reaction chamber is controlled through the double mass flowmeter device, and the configuration is as follows:

[0072] The main carrier gas is argon with a purity of ≥99.9995%, and the total flow rate is 150 sccm to ensure the stability of the reaction atmosphere.

[0073] The branch mixed gas of the double mass flowmeter device is composed of hydrogen (purity ≥99.999%) and hydrogen selenide (purity ≥99.99%), and the flow rate is 5% of the total flow rate. The flow rate ratio of the mixed gas needs to be dynamically adjusted to optimize the supply of selenium source during the reaction process.

[0074] Further, the flow rate ratio of hydrogen selenide in the branch mixed gas should be dynamically adjusted at different stages of epitaxial growth, and the adjustment rule is:

[0075] The initial nucleation stage (0-10 min), the flow rate ratio of hydrogen selenide is 3%, to ensure uniform nucleation of crystal nucleus and preliminary growth of thin film;

[0076] The lateral epitaxial stage (10-60 min), the flow rate ratio of hydrogen selenide is reduced to 1% to avoid excessive supply of selenium source, thereby controlling the thickness and growth rate of the epitaxial film.

[0077] Step three, temperature field and vacuum establishment

[0078] After loading is completed, a high-efficiency vacuum pump is used to evacuate the reaction chamber to a background vacuum of <5x10 -4 Pa, to ensure that the vacuum environment in the reaction chamber can effectively remove residual gas and impurities, thereby providing a stable atmosphere for the subsequent growth process.

[0079] Then the substrate is heated, and the temperature is raised at a rate of 5°C / min to avoid thermal stress cracking or uneven growth of the substrate caused by sudden temperature rise, and then the substrate temperature is raised to 750°C.

[0080] Meanwhile, the temperature gradient is compensated by the partition heating belt, so that the substrate surface temperature uniformity reaches ±1℃. Specifically, an annular auxiliary heating belt (width 5-10mm, power 50-200W adjustable) is added below the double-zone graphite heating block, which surrounds the substrate (distance from the substrate edge 10-15mm). The substrate temperature data is collected in real time by the PID controller (feedback by the infrared temperature measuring instrument). If the edge area temperature is higher than the center by >1℃, the power of the annular heating belt is reduced;

[0081] If it is lower, the power is increased. Finally, the substrate surface temperature uniformity reaches ±1℃. This control can effectively avoid the uneven growth of the thin film caused by uneven temperature, and ensure the quality of the WSe2 thin film.

[0082] Step four, single crystal thin film growth

[0083] In the initial nucleation stage, the mixed gas is again introduced for 5min, and then the precursor heating is carried out, so that the graphite boat A and the graphite boat B are respectively increased to the preset temperature at a rate of 5℃ / min. The preset temperature of the tungsten powder is 850℃, and the preset temperature of the selenium powder is 250℃.

[0084] During the heating process, the heating power of the graphite boat B is dynamically adjusted to maintain the selenium-tungsten vapor ratio at 2.1:1, which is slightly higher than the stoichiometric ratio of 2:1 (the stoichiometric ratio of WSe2 is tungsten:selenium = 1:2, and the corresponding selenium-tungsten vapor ratio should be 2:1).

[0085] Then the temperature (substrate temperature and temperature in graphite boat A and graphite boat B) is maintained during the lateral epitaxy stage, and the mixed gas flow is reduced to 100sccm. This process can effectively control the uniformity and crystal structure of the thin film, and form a single crystal thin film with a thickness of 1nm (corresponding to 1 layer). The precursor heating is turned off, and the growth is stopped.

[0086] In this step, the gas is introduced by step two, vacuum is pumped by step three, and the gas is introduced again by step four. The "fill-pump-fill" cycle realizes exponential improvement of gas purity, avoiding the disadvantages of "single large flow sweeping" (such as flow disturbance causing precursor vapor flow field disorder)

[0087] Step five, post-processing and collection

[0088] The precursor heating is turned off, the mixed gas flow is increased to 200sccm, the reaction chamber is swept for 10min, and then it is slowly cooled to room temperature at a rate of 1℃ / min. The sample is taken out.

[0089] Example three

[0090] The difference between this example and examples one and two is:

[0091] Comprising the following steps:

[0092] Step one, pretreatment of the substrate

[0093] Quartz glass was chosen as the target substrate, and then the substrate was sequentially immersed in acetone, anhydrous ethanol and deionized water, each ultrasonic cleaning for 10 min, the cleaning frequency was 40 kHz, and the power was 100 W;

[0094] After cleaning, it was blown dry with nitrogen (purity ≥ 99.999%), and then placed in a plasma cleaning machine and subjected to plasma treatment in an argon-oxygen mixed gas atmosphere. The plasma treatment parameters were adjusted according to the substrate material, as follows:

[0095] When the substrate was quartz glass, the argon-oxygen volume ratio was 4:1, the power was 60 W, and the treatment time was 7 min. After plasma treatment, the water contact angle of the substrate surface was measured using a contact angle measuring instrument, and the requirement was that the quartz glass was ≤ 50°. After treatment, it was installed in the CVD reaction chamber.

[0096] The other steps were the same as in Example 2.

[0097] The silicon-based scheme of Example 1 was compared with the traditional CVD (silicon-based) scheme. The process of the traditional CVD scheme is briefly described as follows: through acetone / ethanol ultrasonic cleaning for 10 min, deionized water washing and nitrogen blowing, then W (tungsten) powder and Se (selenium) powder were mixed and placed in a single boat (W:Se ≈ 1:4) on the upstream of a horizontal tube furnace, single-zone heating, substrate temperature 700-800℃ (heating rate 10-20℃ / min), during which Ar carrier gas (constant flow 100sccm) was supplied, and finally a one-time nucleation and vertical growth (30-60 min) method was used.

[0098] The results are shown in the following table:

[0099] Performance indicators Example one Conventional CVD Grain size > 200 μm 20-50 μm Thickness non-uniformity ±4％ ±15％～30％ Selenium vacancy density 5 x 10 10 cm -2 ]]> >10 12 cm -2 ]]>

[0100] As shown in the above table, in Example 1, due to the use of fine temperature control and gas flow adjustment, the uniform growth of WSe2 single crystal thin film was effectively promoted, thereby obtaining a larger crystal domain size, showing better crystal quality and the formation of large-size single crystals. At the same time, the precise control of temperature and gas flow during growth made the thin film grow uniformly on the entire substrate, avoiding thickness fluctuations caused by temperature gradients or uneven gas concentration, making the film thickness more uniform. Finally, during the entire growth process, the reaction atmosphere was purer and the temperature was more uniform, and there were fewer vacancies and defects in the growth process of the thin film, thereby forming a single crystal thin film with higher quality.

[0101] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the framework and scope of application of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin films, characterized in that: The method comprises the following steps: Step 1: Pretreatment of substrate Select one of silicon-based, sapphire, quartz glass as the target substrate, then immerse the substrate in acetone, anhydrous ethanol and deionized water in sequence, each for 10 minutes of ultrasonic cleaning, then dry with nitrogen, then place in a plasma cleaning machine and perform plasma treatment in an argon-oxygen mixed gas atmosphere, then install in a CVD reaction chamber; Step 2: Precursor loading Load tungsten powder and selenium powder into graphite boat A and graphite boat B in the CVD reaction chamber in a molar ratio of 1:8-1:12, then introduce mixed gas into the reaction chamber through a double-path mass flowmeter device; Step 3: Temperature field and vacuum establishment After the loading, the reaction chamber is evacuated to a base vacuum of <5 x 10 -4 Pa, and substrate heating is then performed to raise the substrate temperature to 750-850°C. Step 4: Single crystal thin film growth In the initial nucleation stage, introduce mixed gas again for 5 minutes, then heat the precursors, make graphite boat A and graphite boat B reach the preset temperature at 5℃ / min, at the same time, dynamically adjust the heating power of graphite boat B to maintain the selenium-tungsten vapor ratio at 2.1-2.2:1, then maintain the temperature in the lateral epitaxy stage, and reduce the mixed gas flow to 100-150sccm to make the long-range migration of adsorbed atoms epitaxially grow along the crystal nucleus edge to form a single crystal thin film with a thickness of 1-3nm, then turn off the precursor heating and stop the growth; Step 5: Post-treatment and collection Turn off the precursor heating, increase the mixed gas flow to 200sccm, blow the reaction chamber for 10 minutes, then slowly cool to room temperature at a rate of 1-3℃ / min, and take out the sample.

2. The novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin film according to claim 1, characterized in that: In step 1, the plasma treatment parameters are adjusted according to the substrate material, as follows: When the substrate is silicon-based, the argon-oxygen volume ratio is 3:1, the power is 50W, and the treatment time is 5 minutes; When the substrate is sapphire, the argon-oxygen volume ratio is 2:1, the power is 40W, and the treatment time is 3 minutes; When the substrate is quartz glass, the argon-oxygen volume ratio is 4:1, the power is 60W, and the treatment time is 7 minutes.

3. The novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin film according to claim 1, characterized in that: In step 1, after plasma treatment, the water contact angle of the substrate surface is tested using a contact angle measuring instrument, with the requirements being: silicon-based ≤30°, sapphire ≤40°, and quartz glass ≤50°.

4. The method of claim 1, wherein the method is characterized by: In step 2, the main path carrier gas of the double-path mass flowmeter device is argon with a purity of ≥99.9995%, and the total flow is 150-200sccm; The branch mixed gas of the double-path mass flowmeter device is composed of hydrogen and hydrogen selenide, and the flow is 5%-25% of the total flow.

5. The novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin film according to claim 4, characterized in that: In step 2, the flow ratio of hydrogen selenide in the branch mixed gas is dynamically adjusted, with the adjustment rules being: In the initial nucleation stage, the flow ratio of hydrogen selenide is 3%-5%; In the lateral epitaxy stage, the flow ratio of hydrogen selenide is reduced to 1%-2%.

6. The method of claim 1, wherein the method is a novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin films. In step 3, the temperature is increased at a rate of 5-10℃ / min.

7. The method of claim 1, wherein the method is a novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin films. In step 3, the temperature gradient is compensated by zoned heating to make the substrate surface temperature uniformity reach ±1℃.

8. The novel vapor phase epitaxy growth method of high-quality WSe2 single-crystal thin film according to claim 1, characterized in that: In step 4, the preset temperature of the tungsten powder is 850-900℃, and the preset temperature of the selenium powder is 250-300℃.

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