A method for preparing multilayer molybdenum disulfide thin films

Abstract

This invention provides a method for preparing a multilayer molybdenum disulfide thin film, belonging to the field of thin film material preparation technology. In this invention, an ammonium tetrathiomolybdate solution is coated onto one side of a first substrate. After removing the mixed organic solvent, a solid thin film is formed. The resulting first substrate-solid thin film workpiece is pre-annealed to transform the solid thin film into a precursor film. A second substrate is then stacked on the surface of the precursor film in the resulting first substrate-precursor thin film workpiece. Bonding and annealing processes are performed sequentially, resulting in the multilayer molybdenum disulfide thin film between the first and second substrates. This invention utilizes bonding technology to reduce film quality damage during annealing, enabling the production of high-quality multilayer molybdenum disulfide thin films while shortening the processing time.

Description

Technical Field

[0001] This invention relates to the field of thin film material preparation technology, and in particular to a method for preparing multilayer molybdenum disulfide thin films. Background Technology

[0002] Molybdenum disulfide (MoS2) is a graphene-like two-dimensional (2D) van der Waals material. When the size of MoS2 is reduced from bulk form to two-dimensional single-layer or multi-layer sheets, the band gap changes from an indirect band gap to a direct band gap, and it can be thinned to atomic thickness while maintaining or enhancing its overall electrical and optical properties. Because of this, MoS2 has enormous potential for future electronic and optoelectronic miniaturization, enabling devices that surpass the limitations of traditional semiconductors and move towards the goal of atomic-level devices.

[0003] Despite its enormous potential, the industrialization of MoS2 thin films has been hampered. The main challenge is the excessively long growth time, which limits the total production volume of MoS2 films. Currently, MoS2 film preparation remains in the laboratory research stage. The most commonly used MoS2 film preparation techniques in laboratories include: 1. Chemical vapor deposition (CVD) using MoO3 or MoCl5 precursors, which typically requires a total heat treatment time of 4–6 hours; 2. Large-area MoS2 films can also be prepared by flowing hot sulfur vapor over a molybdenum precursor in a vacuum tube furnace, which, in addition to the external metal deposition step, also requires 4–6 hours; 3. Organometallic chemical vapor deposition (MOCVD) can prepare higher-quality MoS2 films, but requires an even longer total heat treatment time, exceeding 24 hours. In summary, how to achieve large-scale preparation of high-quality multilayer MoS2 films is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing multilayer molybdenum disulfide thin films. The method provided by this invention can obtain high-quality multilayer molybdenum disulfide thin films while shortening the processing time.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a multilayer molybdenum disulfide thin film, comprising the following steps:

[0007] Ammonium tetrathiomolybdate was mixed with a mixed organic solvent to obtain an ammonium tetrathiomolybdate solution;

[0008] The ammonium tetrathiomolybdate solution is coated on one side of the first substrate, the mixed organic solvent in the ammonium tetrathiomolybdate solution is removed, and a solid film is formed on one side of the first substrate to obtain a first substrate-solid film workpiece.

[0009] The first substrate-solid thin film workpiece is pre-annealed to convert the solid thin film into a precursor thin film, thus obtaining the first substrate-precursor thin film workpiece.

[0010] A second substrate is stacked on the surface of the precursor thin film in the first substrate-precursor thin film workpiece, and bonding treatment is performed to obtain the first substrate-precursor thin film-second substrate workpiece.

[0011] The first substrate-precursor film-second substrate workpiece is annealed to obtain the multilayer molybdenum disulfide film between the first substrate and the second substrate.

[0012] Preferably, the mixed organic solvent is a mixture of N-methylpyrrolidone, n-butylamine, and monoethanolamine, or a mixture of N,N-dimethylformamide, n-butylamine, and monoethanolamine; the volume ratio of N-methylpyrrolidone, n-butylamine, and monoethanolamine in the mixture of N-methylpyrrolidone, n-butylamine, and monoethanolamine is 4.5–5:1.5–2:1; the volume ratio of N,N-dimethylformamide, n-butylamine, and monoethanolamine in the mixture of N,N-dimethylformamide, n-butylamine, and monoethanolamine is 4.5–5:1.5–2:1.

[0013] Preferably, the concentration of ammonium tetrathiomolybdate in the ammonium tetrathiomolybdate solution is 4–8 mg / mL.

[0014] Preferably, the first substrate and the second substrate independently comprise a sapphire wafer, a silicon substrate, or a glass substrate.

[0015] Preferably, the method for removing the mixed organic solvent from the ammonium tetrathiomolybdate solution is heat treatment, wherein the temperature of the heat treatment is 130-150°C and the time is 3-5 min.

[0016] Preferably, the bonding treatment conditions include: a temperature of 100–120°C, a pressure of 13000–15000 N, and a time of 40–60 min.

[0017] Preferably, the pre-annealing treatment is performed at a temperature of 350–400°C for a holding time of 20–30 min; the annealing treatment is performed at a temperature of 900–1000°C for a holding time of 10–20 min.

[0018] Preferably, the heating rate to the temperature required for the pre-annealing treatment and the annealing treatment is independently 10-15°C / s.

[0019] Preferably, the pre-annealing treatment further includes: cooling to room temperature at a first cooling rate; the annealing treatment further includes: cooling to room temperature at a second cooling rate; wherein the first cooling rate and the second cooling rate are independently 5-10℃ / s.

[0020] Preferably, the pre-annealing treatment is carried out in the presence of a protective gas and hydrogen, wherein the volume fraction of hydrogen is 5-10%; and the total pressure of the protective gas and hydrogen during the pre-annealing treatment is 0.5-1 standard atmosphere.

[0021] The annealing process is carried out in the presence of a protective gas, and the pressure of the protective gas during the annealing process is 0.5 to 1 standard atmosphere.

[0022] The pre-annealing and annealing processes are carried out in a rapid heat treatment annealing furnace.

[0023] This invention provides a method for preparing a multilayer molybdenum disulfide thin film, comprising the following steps: mixing ammonium tetrathiomolybdate with a mixed organic solvent to obtain an ammonium tetrathiomolybdate solution; coating the ammonium tetrathiomolybdate solution onto one side of a first substrate, removing the mixed organic solvent from the ammonium tetrathiomolybdate solution, forming a solid film on one side of the first substrate, obtaining a first substrate-solid film workpiece; pre-annealing the first substrate-solid film workpiece to convert the solid film into a precursor film, obtaining a first substrate-precursor film workpiece; stacking a second substrate on the surface of the precursor film in the first substrate-precursor film workpiece, and performing a bonding process to obtain a first substrate-precursor film-second substrate workpiece; annealing the first substrate-precursor film-second substrate workpiece to obtain the multilayer molybdenum disulfide thin film between the first substrate and the second substrate. This invention utilizes bonding technology to reduce film quality damage during annealing, and can obtain a high-quality multilayer molybdenum disulfide thin film while shortening the processing time. Meanwhile, the present invention uses a coating method to prepare multilayer molybdenum disulfide thin films, which can realize the large-area growth of multilayer continuous molybdenum disulfide thin films, and solves the problems of limited film growth area and film discontinuity in traditional growth methods.

[0024] Furthermore, this invention does not require expensive and complex equipment, such as a rapid thermal annealing furnace, to achieve the preparation of high-quality multilayer molybdenum disulfide films, which greatly reduces costs. Moreover, the rapid thermal annealing furnace can grow up to 8-inch multilayer molybdenum disulfide films, effectively solving the problem of low output and low efficiency of existing growth equipment, which prevents large-scale industrial production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the rapid heat treatment annealing furnace used to prepare the multilayer molybdenum disulfide thin film in Example 1;

[0026] Figure 2 The image shows a physical photograph of the multilayer molybdenum disulfide thin film prepared in Example 1.

[0027] Figure 3This is a high-resolution optical microscope image of the multilayer molybdenum disulfide thin film prepared in Example 1;

[0028] Figure 4 The Raman spectrum of the multilayer molybdenum disulfide thin film prepared in Example 1;

[0029] Figure 5 Comparative diagrams of the multilayer molybdenum disulfide films prepared in Examples 1-3. Detailed Implementation

[0030] This invention provides a method for preparing a multilayer molybdenum disulfide thin film, comprising the following steps:

[0031] Ammonium tetrathiomolybdate was mixed with a mixed organic solvent to obtain an ammonium tetrathiomolybdate solution;

[0032] The ammonium tetrathiomolybdate solution is coated on one side of the first substrate, the mixed organic solvent in the ammonium tetrathiomolybdate solution is removed, and a solid film is formed on one side of the first substrate to obtain a first substrate-solid film workpiece.

[0033] The first substrate-solid thin film workpiece is pre-annealed to convert the solid thin film into a precursor thin film, thus obtaining the first substrate-precursor thin film workpiece.

[0034] A second substrate is stacked on the surface of the precursor thin film in the first substrate-precursor thin film workpiece, and bonding treatment is performed to obtain the first substrate-precursor thin film-second substrate workpiece.

[0035] The first substrate-precursor film-second substrate workpiece is annealed to obtain the multilayer molybdenum disulfide film between the first substrate and the second substrate.

[0036] In this invention, unless otherwise specified, all raw materials used are commercially available products known to those skilled in the art, and all equipment used is equipment known to those skilled in the art.

[0037] This invention involves mixing ammonium tetrathiomolybdate with a mixed organic solvent to obtain an ammonium tetrathiomolybdate solution. In this invention, the mixed organic solvent is preferably a mixture of N-methylpyrrolidone, n-butylamine, and monoethanolamine, or a mixture of N,N-dimethylformamide, n-butylamine, and monoethanolamine; the volume ratio of N-methylpyrrolidone, n-butylamine, and monoethanolamine in the mixture is 4.5–5:1.5–2:1, more preferably 5:2:1; the volume ratio of N,N-dimethylformamide, n-butylamine, and monoethanolamine in the mixture is preferably 4.5–5:1.5–2:1, more preferably 2.5:1:0.5. In this invention, the concentration of ammonium tetrathiomolybdate in the ammonium tetrathiomolybdate solution is preferably 4–8 mg / mL, more preferably 5–6 mg / mL. In this invention, the components in a mixed organic solvent are subjected to a first ultrasonic mixing, followed by the addition of ammonium tetrathiomolybdate to the resulting mixed organic solvent for a second ultrasonic mixing, thereby obtaining the ammonium tetrathiomolybdate solution. In this invention, the first and second ultrasonic mixing times are preferably 25–35 min, more preferably 30 min; this invention does not impose any particular limitation on the ultrasonic power of the first and second ultrasonic mixing.

[0038] After obtaining the ammonium tetrathiomolybdate solution, the present invention coats the ammonium tetrathiomolybdate solution onto one side of a first substrate, removes the mixed organic solvent in the ammonium tetrathiomolybdate solution, and forms a solid film on one side of the first substrate, thereby obtaining a first substrate-solid film workpiece. In the present invention, the first substrate preferably includes a sapphire wafer, a silicon substrate, or a glass substrate, more preferably a sapphire wafer. In the present invention, the first substrate is preferably pretreated before use, and the pretreatment preferably includes sequential cleaning, drying, and oxygen treatment; the cleaning is preferably ultrasonic cleaning, and the reagents used for ultrasonic cleaning are preferably acetone, anhydrous ethanol, and deionized water, respectively, and the ultrasonic cleaning time for each reagent is preferably 10-20 min, more preferably 15-20 min; the drying method is preferably nitrogen blowing; the oxygen treatment is preferably carried out in a UV photo-oxidation treatment device, and the oxygen treatment time is preferably 2-5 min, more preferably 2-3 min.

[0039] The present invention preferably involves coating one side of the pretreated first substrate with the ammonium tetrathiomolybdate solution; the coating method is preferably spin coating, and the equipment used for spin coating is preferably a spin coater. In the present invention, the spin coating preferably includes performing a first spin coating and a second spin coating sequentially; the conditions for the first spin coating include: the initial rotation speed is preferably 300-500 rpm, more preferably 400-500 rpm; the time is preferably 5-10 s, more preferably 5-7 s; the acceleration is preferably 100-300 rpm, more preferably 100-200 rpm; the conditions for the second spin coating include: the initial rotation speed is preferably 2000-2500 rpm, more preferably 2400-2500 rpm; the time is preferably 30-60 s, more preferably 30-40 s; the acceleration is preferably 300-500 rpm, more preferably 300-400 rpm.

[0040] After the coating is completed, the present invention removes the mixed organic solvent from the ammonium tetrathiomolybdate solution and forms a solid film on one side of the first substrate to obtain a first substrate-solid film workpiece. In the present invention, the method for removing the mixed organic solvent from the ammonium tetrathiomolybdate solution is preferably heat treatment. The temperature of the heat treatment is preferably 130–150°C, more preferably 140–150°C; the time is preferably 3–5 min, more preferably 4–5 min. In embodiments of the present invention, the heat treatment is preferably performed on a hot plate.

[0041] After obtaining the first substrate-solid thin film workpiece, the present invention performs a pre-annealing treatment on the first substrate-solid thin film workpiece to convert the solid film into a precursor film, thereby obtaining the first substrate-precursor thin film workpiece. In the present invention, the temperature of the pre-annealing treatment is preferably 350-400℃, more preferably 380-400℃; the holding time is preferably 20-30 min, more preferably 20-25 min; the heating rate to the temperature required for the pre-annealing treatment is preferably 10-15℃ / s, more preferably 13-15℃ / s; the pre-annealing treatment is preferably carried out in the presence of a protective gas and hydrogen, wherein the volume fraction of hydrogen is preferably 5-10%, more preferably 5-7%; the protective gas is preferably nitrogen; the total pressure of the protective gas and hydrogen during the pre-annealing treatment is preferably 0.5-1 standard atmospheres, more preferably 0.8-1 standard atmospheres. In an embodiment of the present invention, the pre-annealing treatment is performed in a rapid thermal annealing furnace. Specifically, the first substrate-solid film workpiece is placed in the cavity of the rapid thermal annealing furnace for gas purging to prevent a large amount of residual oxygen in the cavity. Then, a protective gas and hydrogen are introduced, and the temperature is raised to the required temperature for pre-annealing at the aforementioned heating rate. In the present invention, the gas purging method preferably includes: first, evacuating the vacuum for 2 minutes to achieve a vacuum degree of 15 Pa, then introducing nitrogen at 1 standard atmosphere, and then evacuating the vacuum for 6-10 minutes to achieve a vacuum degree of 4.5 Pa. In the present invention, the pre-annealing treatment preferably further includes: cooling to room temperature at a first cooling rate; the first cooling rate is preferably 5-10°C / s, more preferably 5-7°C / s.

[0042] In this invention, during the pre-annealing process, ammonium tetrathiomolybdate ((NH4)2MoS4) decomposes into MoS2, while excess substances in the ammonium tetrathiomolybdate are released in gaseous form, such as NH3 and H2S. Hydrogen accelerates the decomposition of ammonium tetrathiomolybdate and prevents MoS2 from being oxidized to MoS3. The relevant reaction formula is: (NH4)2MoS4 + H2 → MoS2 + NH3 + H2S. Although ammonium tetrathiomolybdate decomposes into MoS2 during the pre-annealing process, the resulting film quality is poor. Therefore, subsequent annealing is required to improve the film quality through high-temperature crystallization.

[0043] After obtaining the first substrate-precursor thin film workpiece, the present invention places a second substrate on the surface of the precursor thin film in the first substrate-precursor thin film workpiece and performs bonding processing to obtain the first substrate-precursor thin film-second substrate workpiece. In the present invention, the optional type of the second substrate is preferably the same as the known type of the first substrate, and will not be described again here; the second substrate is preferably pretreated before use, and the method of pretreatment of the second substrate is preferably the same as the method of pretreatment of the first substrate, and will not be described again here. In the present invention, the bonding processing conditions include: the temperature is preferably 100-120°C, more preferably 100-110°C; the pressure is preferably 13000-15000N, more preferably 14000-15000N; and the time is preferably 40-60min, more preferably 40-50min. In the embodiments of the present invention, the bonding processing is specifically performed in a bonding machine. In this invention, the film quality after pre-annealing is poor, requiring further annealing at higher temperatures to crystallize the film and improve its quality. However, MoS2 evaporates very easily at higher temperatures, and the S atoms in MoS2 are unstable and easily diffuse, leading to a decrease in film quality. This invention uses bonding to obtain a first substrate-precursor film-second substrate workpiece, which reduces the redissolution and evaporation of MoS2 during subsequent annealing. Furthermore, the closer the precursor film is to the substrate (by bonding the entire structure of the first substrate-precursor film-second substrate, reducing the distance between the precursor film and the substrate), the more likely the diffused S atoms are to be reflected back into the precursor film, thus improving film quality.

[0044] After obtaining the first substrate-precursor film-second substrate workpiece, the present invention performs an annealing treatment on the first substrate-precursor film-second substrate workpiece to obtain the multilayer molybdenum disulfide film between the first substrate and the second substrate. In the present invention, the annealing temperature is preferably 900-1000℃, more preferably 950℃; the holding time is preferably 10-20 min, more preferably 15-20 min; the heating rate to the required annealing temperature is preferably 10-15℃ / s, more preferably 13-15℃ / s; the annealing treatment is preferably carried out in the presence of a protective gas, preferably nitrogen; the pressure of the protective gas during the annealing treatment is preferably 0.5-1 standard atmosphere, more preferably 0.8-1 standard atmosphere. In an embodiment of the present invention, the annealing process is performed in a rapid thermal annealing furnace. Specifically, the first substrate-precursor film-second substrate workpiece is placed in the chamber of the rapid thermal annealing furnace for gas purging to prevent a large amount of residual oxygen in the chamber. Then, a protective gas is introduced, and the temperature is raised to the required annealing temperature at the aforementioned heating rate for annealing. In the present invention, the gas purging method preferably includes: first, evacuating the vacuum for 2 minutes to achieve a vacuum degree of 15 Pa, then introducing nitrogen at 1 standard atmosphere, and then evacuating the vacuum for 6-10 minutes to achieve a vacuum degree of 4.5 Pa. In the present invention, the annealing process preferably further includes: cooling to room temperature at a second cooling rate; the second cooling rate is preferably 5-10°C / s, more preferably 5-7°C / s.

[0045] In this invention, after the annealing process is completed, the multilayer molybdenum disulfide film is obtained between the first substrate and the second substrate. The multilayer molybdenum disulfide film is grown on the surface of the first substrate, and the second substrate can be directly detached. Subsequently, this invention preferably peels the multilayer molybdenum disulfide film off the surface of the first substrate as needed. Specifically, the first substrate on which the multilayer molybdenum disulfide film is grown can be immersed in a potassium hydroxide solution for 1 hour to achieve the peeling of the multilayer molybdenum disulfide film.

[0046] The method of this invention can prepare continuous and uniform multilayer molybdenum disulfide films, suitable for large-scale industrial production. In this invention, the number of layers in the multilayer molybdenum disulfide film is preferably 2 to 7, specifically 2, 3, 4, 5, 6, or 7 layers; the total thickness of the multilayer molybdenum disulfide film is preferably 1.36 to 4.76 nm, specifically 1.36 nm, 2.04 nm, 2.72 nm, 3.40 nm, 4.08 nm, or 4.76 nm; the diameter of the multilayer molybdenum disulfide film is preferably 1 to 8 inches, more preferably 4 to 6 inches.

[0047] Figure 1This is a schematic diagram of the rapid thermal annealing furnace used to prepare multilayer molybdenum disulfide thin films in Example 1. It includes a centrally located substrate for placing samples and heating lamps positioned above and below the substrate. It also has an evacuation port and two air inlets above the evacuation port.

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] Example 1

[0050] S1: Mix 2.5 mL of N,N-dimethylformamide, 1 mL of n-butylamine and 0.5 mL of monoethanolamine, sonicate for 30 min, add 16 mg of ammonium tetrathiomolybdate powder to the resulting mixed organic solvent, and then sonicate for another 30 min to obtain an ammonium tetrathiomolybdate solution.

[0051] S2: Two sapphire wafers (referred to as the first sapphire substrate and the second sapphire substrate, respectively) are ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 20 min each, dried with nitrogen, and then placed in a UV photo-oxidation treatment device for oxygen treatment for 2 min. The ammonium tetrathiomolybdate solution is dropped onto the oxygen-treated first sapphire substrate and spread evenly on a spin coater. The operating conditions of the spin coater are: initial speed of 500 rpm and acceleration of 100 rpm for 5 s, then initial speed of 2500 rpm and acceleration of 300 rpm for 30 s. After spreading, the substrate is placed on a 150℃ hot stage and heated for 5 min to remove the mixed organic solvent in the ammonium tetrathiomolybdate solution, forming a solid film on one side of the first sapphire substrate, thus obtaining the first sapphire substrate-solid film workpiece.

[0052] S3: Place the first sapphire substrate-solid film workpiece into the cavity of the rapid thermal annealing furnace, close the cavity door, and evacuate the rapid thermal annealing furnace for 2 minutes to achieve a vacuum of 15 Pa. Then, introduce nitrogen gas at 1 atmosphere and evacuate for another 6 minutes to achieve a vacuum of 4.5 Pa to purge the rapid thermal annealing furnace. After purging, introduce nitrogen gas with a volume fraction of 95% and hydrogen gas with a volume fraction of 5% into the cavity. The total pressure of the nitrogen and hydrogen gas introduced into the cavity is 1 atmosphere. Then, heat the rapid thermal annealing furnace from room temperature (25°C) to 400°C at a heating rate of 15°C / s for pre-annealing for 20 minutes. After the pre-annealing, cool the rapid thermal annealing furnace to room temperature at a cooling rate of 5°C / s to form a precursor film on the surface of the first sapphire substrate, thus obtaining the first sapphire substrate-precursor film workpiece.

[0053] S4: Place an oxygen-treated second sapphire substrate (i.e., the overall structure is first sapphire substrate-precursor film-second sapphire substrate) on the surface of the precursor film in the first sapphire substrate-precursor film workpiece, and perform bonding treatment for 10 minutes at a temperature of 100℃ and a pressure of 15000N using a bonding machine to obtain the first sapphire substrate-precursor film-second sapphire substrate workpiece.

[0054] S5: Place the first sapphire substrate-precursor film-second sapphire substrate workpiece into the cavity of the rapid heat treatment annealing furnace, close the cavity door, and evacuate the rapid heat treatment annealing furnace for 2 minutes to achieve a vacuum degree of 15 Pa. Then, introduce nitrogen gas at 1 atmosphere and evacuate for another 6 minutes to achieve a vacuum degree of 4.5 Pa to purge the rapid heat treatment annealing furnace. After purging, introduce nitrogen gas at 1 atmosphere into the cavity, and then heat the rapid heat treatment annealing furnace from room temperature to 950°C at a heating rate of 15°C / s for annealing for 10 minutes. After annealing, at a cooling rate... To achieve this, a rapid heat treatment annealing furnace was cooled to room temperature at 5℃ / s, resulting in a continuous and uniform multilayer molybdenum disulfide film between a first sapphire substrate and a second sapphire substrate. (The multilayer molybdenum disulfide film is grown on the surface of the first sapphire substrate, and the second sapphire substrate can be directly detached. Subsequently, the multilayer molybdenum disulfide film can be peeled off from the surface of the first substrate as needed. Specifically, the first sapphire substrate with the multilayer molybdenum disulfide film can be immersed in a potassium hydroxide solution for 1 hour to achieve the peeling of the multilayer molybdenum disulfide film.) The multilayer molybdenum disulfide film has two layers, a total thickness of 1.36 nm, and a diameter of 4 inches.

[0055] Figure 2The image shown is a physical picture of the multilayer molybdenum disulfide film prepared in Example 1. The results show that the multilayer molybdenum disulfide film prepared by the present invention using a rapid heat treatment annealing furnace is continuous and uniformly formed, indicating that the method of the present invention has successfully prepared a large-scale continuous multilayer molybdenum disulfide film.

[0056] Figure 3 The image shown is a high-resolution optical microscope image of the multilayer molybdenum disulfide thin film prepared in Example 1. The results show that the surface of the multilayer molybdenum disulfide thin film is clean and continuous. At the same time, the scratches indicate that the multilayer molybdenum disulfide thin film has good adhesion to the sapphire wafer.

[0057] Figure 4 The image shows the Raman spectrum of the multilayer molybdenum disulfide thin film prepared in Example 1. The results show that the EL of the multilayer molybdenum disulfide thin film prepared by the rapid thermal annealing furnace in this invention is significantly higher than that of the original film. 1 The characteristic peaks of 2g and A1g are located at 384.6 cm⁻¹. -1 and 407.9cm -1 The difference is 23.3cm. -1 The results are consistent with those in the literature (H.Li, Q.Zhang, CCRYap, BKTay, THTEdwin, A.Olivier, et al. From Bulk to Monolayer MoS2: Evolution of Raman Scattering, Advanced Functional Materials, 22(7), 2012, 1385-1390), further proving that the present invention has prepared a high-quality multilayer molybdenum disulfide film.

[0058] Example 2

[0059] Multilayer molybdenum disulfide films were prepared according to the method of Example 1, except that the amount of ammonium tetrathiomolybdate powder used in this example was 24 mg; the number of layers of multilayer molybdenum disulfide films in this example was 4, and the total thickness was 2.72 nm.

[0060] Example 3

[0061] Multilayer molybdenum disulfide films were prepared according to the method of Example 1, except that the amount of ammonium tetrathiomolybdate powder used in this example was 32 mg; the number of layers of multilayer molybdenum disulfide films in this example was 7, and the total thickness was 4.76 nm.

[0062] Figure 5Comparative images of the multilayer molybdenum disulfide films prepared in Examples 1-3 are shown, where a and b are optical and microscopic images of a clean sapphire wafer and a multilayer molybdenum disulfide film, respectively, and c and d are AFM images of the multilayer molybdenum disulfide film. The results show that the thickness of the multilayer molybdenum disulfide film is increased with the increase of the amount of ammonium tetrathiomolybdate powder.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multilayer molybdenum disulfide thin film, characterized in that, Includes the following steps: Ammonium tetrathiomolybdate was mixed with a mixed organic solvent to obtain an ammonium tetrathiomolybdate solution; The ammonium tetrathiomolybdate solution is coated on one side of the first substrate, the mixed organic solvent in the ammonium tetrathiomolybdate solution is removed, and a solid film is formed on one side of the first substrate to obtain a first substrate-solid film workpiece. The first substrate-solid thin film workpiece is pre-annealed to convert the solid thin film into a precursor thin film, thus obtaining the first substrate-precursor thin film workpiece. The pre-annealing treatment is performed at a temperature of 350–400°C for 20–30 minutes. A second substrate is stacked on the surface of the precursor thin film in the first substrate-precursor thin film workpiece, and bonding treatment is performed to obtain the first substrate-precursor thin film-second substrate workpiece. The bonding process conditions include: a temperature of 100–120°C, a pressure of 13000–15000 N, and a time of 40–60 min; The first substrate-precursor film-second substrate workpiece is annealed to obtain the multilayer molybdenum disulfide film between the first substrate and the second substrate; the annealing temperature is 950-1000℃ and the holding time is 10-20min; the annealing is carried out in the presence of a protective gas and the pressure of the protective gas during the annealing process is 0.5-1 standard atmosphere.

2. The preparation method according to claim 1, characterized in that, The mixed organic solvent is a mixture of N-methylpyrrolidone, n-butylamine, and monoethanolamine, or a mixture of N,N-dimethylformamide, n-butylamine, and monoethanolamine; the volume ratio of N-methylpyrrolidone, n-butylamine, and monoethanolamine in the mixture of N-methylpyrrolidone, n-butylamine, and monoethanolamine is 4.5–5:1.5–2:1; the volume ratio of N,N-dimethylformamide, n-butylamine, and monoethanolamine in the mixture of N,N-dimethylformamide, n-butylamine, and monoethanolamine is 4.5–5:1.5–2:

1.

3. The preparation method according to claim 2, characterized in that, The concentration of ammonium tetrathiomolybdate in the ammonium tetrathiomolybdate solution is 4–8 mg / mL.

4. The preparation method according to claim 1, characterized in that, The first substrate and the second substrate independently comprise a sapphire wafer, a silicon substrate, or a glass substrate.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The mixed organic solvent in the ammonium tetrathiomolybdate solution is removed by heat treatment, wherein the temperature of the heat treatment is 130-150°C and the time is 3-5 min.

6. The preparation method according to claim 1, characterized in that, The heating rate to the temperature required for the pre-annealing treatment and the annealing treatment is independent of each other and is 10-15°C / s.

7. The preparation method according to claim 1, characterized in that, The pre-annealing treatment further includes: cooling to room temperature at a first cooling rate; the annealing treatment further includes: cooling to room temperature at a second cooling rate; the first cooling rate and the second cooling rate are independent and are 5-10℃ / s.

8. The preparation method according to claim 1, 6, or 7, characterized in that, The pre-annealing treatment is carried out in the presence of a protective gas and hydrogen, wherein the volume fraction of hydrogen is 5-10%; the total pressure of the protective gas and hydrogen during the pre-annealing treatment is 0.5-1 standard atmosphere. The pre-annealing and annealing processes are carried out in a rapid heat treatment annealing furnace.

Images