A method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide film on a liquid phase layer surface

Abstract

The application relates to the field of new materials, in particular to a method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide film on a liquid phase layer surface. The method specifically comprises the following steps: depositing a non-metallic element capable of forming a low-melting-point alloy phase with gold on the surface of a clean gold substrate by physical vapor deposition under an argon atmosphere; annealing the substrate treated above under certain parameters to build an alloy surface layer and use the alloy surface layer as a growth substrate; introducing a volatile sulfur source and a molybdenum source at high temperature to grow a uniform multilayer molybdenum-based transition metal chalcogenide film. The thickness of the alloy surface layer, the atmosphere and the growth temperature are adjusted to control the number of layers of the molybdenum-based transition metal chalcogenide film. The method can be used to prepare a high-quality and uniform-thickness multilayer molybdenum-based transition metal chalcogenide film, lays a foundation for the application of the molybdenum-based transition metal chalcogenide in the fields of nanoelectronic devices and photoelectric devices, and can be widely applied to the field of thin film chemical vapor deposition preparation.

Description

Technical Field

[0001] This invention relates to the field of new materials, specifically to a method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of a liquid phase layer. The method combines physical vapor deposition (PVD) and chemical vapor deposition (CVD) to prepare the thin film. The PVD method is used to prepare an alloy-pure metal composite substrate, and the substrate is used to grow high-quality uniform multilayer molybdenum-based transition metal chalcogenide thin films. This method is expected to be extended to the field of large-area thin film preparation. Background Technology

[0002] Two-dimensional transition metal chalcogenides (TMCs) are novel two-dimensional materials with unique properties in optoelectronics and electrocatalysis. They possess stable structures and excellent electronic, optical, mechanical, chemical, and thermal properties. These materials have a two-dimensional layered structure similar to graphene, with layers held together by weak van der Waals forces. However, they differ significantly from graphene in structure and properties. Taking molybdenum disulfide (MoD) as an example, a single layer of MoD consists of a central molybdenum atom flanked by sulfur atoms. With varying numbers of MoD layers, the material undergoes a transition from a direct bandgap to an indirect bandgap, and the bandgap can be adjusted within a range of 1.2 eV to 1.8 eV. This makes it one of the most promising two-dimensional materials for current applications, and the preparation of high-quality multilayer MoD film is fundamental to its outstanding performance in various fields.

[0003] Although molybdenum-based transition metal chalcogenides (TMCs) can now be mechanically exfoliated from bulk materials, this method is inefficient, uncontrollable, and unable to produce large-area films with uniform thickness. Chemical vapor deposition (CVD) is currently one of the most efficient methods for preparing MTCs, offering advantages such as high efficiency, good growth quality, and high controllability. However, controlling the number of MTC film layers remains a challenge in CCV. This is because the CCV process often requires the volatilization of a solid precursor as a growth source, and this volatilization process is often characterized by inhomogeneity and low rates. This results in a growth rate gradient on the substrate (i.e., the growth rate near the source is greater than that far from the source), leading to uneven thickness and slow growth rates. Under these conditions, it is often difficult to prepare uniform, multilayered MTCs. Therefore, efficiently growing high-quality, uniformly layered MTCs remains a challenge, significantly limiting the application of MTCs in various fields.

[0004] Magnetron sputtering, thermal evaporation, and electron beam evaporation in physical vapor deposition (PVD) are traditional thin film preparation processes with advantages such as low cost, good controllability, and scalability. They are currently commonly used methods in industrial thin film preparation. This approach is characterized by process compatibility, high efficiency, and high controllability, and can be combined with chemical vapor deposition (CVD) to improve the controllability of the growth process and ultimately enhance the quality of molybdenum-based transition metal chalcogenide thin films. However, the key to this process lies in how to more effectively combine the aforementioned two methods, utilizing their synergistic effect to significantly improve the quality of the prepared thin film. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on a liquid phase surface. This method utilizes physical vapor deposition (PVD) to pretreat the substrate, constructing a liquid-solid composite substrate composed of an alloy and a pure-phase metal. The solid gold substrate possesses a certain amount of dissolved molybdenum, while the liquid structure exhibits a low melting point, ensuring it remains liquid at the growth temperature and serves as a diffusion channel for molybdenum atoms. This develops a method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films. The thickness of the molybdenum-based transition metal chalcogenide thin film can be controlled by adjusting parameters such as the liquid layer thickness, atmosphere, and growth temperature. This method offers advantages such as high efficiency, high controllability, and high-quality film samples, and can serve as a method for preparing uniform multilayer molybdenum-based transition metal chalcogenide continuous thin films.

[0006] The technical solution of the present invention:

[0007] A method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on a liquid phase layer surface involves physical vapor deposition of a non-metallic thin film with a thickness of 25-500 nm on a gold substrate surface after a cleaning process and annealing at 800-1200℃ for 5-15 hours. This film can form a low-melting-point alloy with gold. After a second annealing, a liquid-solid composite substrate composed of a liquid alloy and gold is constructed at high temperatures. The solid phase structure constructed by gold has a high melting point, does not react with sulfur, and has a certain amount of molybdenum solubility, serving as a storage and supply source for molybdenum. The liquid layer constructed by the liquid alloy has a low melting point and remains liquid at a high growth temperature, covering the surface of the gold substrate solid phase structure with a high melting point and a certain amount of molybdenum solubility, acting as a molybdenum diffusion layer. Using chemical vapor deposition, a structure of liquid alloy encapsulating a solid gold substrate is formed at the growth temperature. By adjusting the thickness of the liquid layer and the growth temperature and atmosphere parameters, a uniform multilayer molybdenum-based transition metal chalcogenide thin film is prepared by controlling the diffusion of molybdenum atoms in the liquid layer.

[0008] The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer involves forming a stable liquid-solid structure at the growth temperature. A non-metallic thin film that can form a low-melting-point alloy with gold is prepared by physical vapor deposition and covered on the upper surface of a gold substrate with a high melting point and a certain amount of dissolved molybdenum.

[0009] The method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of the liquid phase layer comprises an alloy and a gold substrate constituting a liquid-solid composite substrate. The gold substrate has catalytic activity and a certain solubility for molybdenum, with a purity greater than 99.9 wt% and a thickness greater than 50 micrometers.

[0010] The method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of the liquid phase layer comprises an alloy and a gold substrate constituting a liquid-solid composite substrate. The alloy is formed by the combination of gold and one or two non-metallic elements at high temperature. These non-metallic elements include, but are not limited to, one or more of silicon, germanium, gallium, and antimony. The alloy is required to have a low melting point and be liquid at the growth temperature.

[0011] The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer involves depositing non-metallic elements onto a clean gold substrate surface via physical vapor deposition, such as magnetron sputtering or thermal evaporation. To construct a liquid alloy surface layer at the growth temperature, the substrate with deposited non-metallic elements is annealed at 900–1100°C in hydrogen or a hydrogen-containing mixed gas, wherein the volume ratio of hydrogen is not less than 5%, the gas flow rate is 500–1000 s·ccm, and the annealing time is 0.5–10 h.

[0012] The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer, wherein the process for preparing a multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer is as follows:

[0013] The first stage involves using a liquid-solid composite substrate composed of an alloy and gold as the growth substrate, and selecting a gaseous, liquid, or solid sulfur source. At the growth temperature, a liquid-solid stacked structure is constructed with a liquid alloy layer covering a solid pure gold layer. With the assistance of a carrier gas, a monolayer of molybdenum-based transition metal chalcogenide film is first grown on the surface of the liquid alloy. At the same time, some molybdenum atoms pass through the liquid alloy layer and are pre-stored in a gold substrate with a certain amount of dissolved molybdenum.

[0014] The second stage involves fine-tuning the growth atmosphere and slowly lowering the reaction temperature to release molybdenum atoms pre-stored in the solid gold matrix. These atoms then diffuse controllably through the liquid alloy layer to the space between the liquid surface and the monolayer molybdenum-based transition metal chalcogenide, where they react with the chalcogen elements that have diffused into this gap, ultimately forming a multilayer molybdenum-based transition metal chalcogenide film with a uniform number of layers.

[0015] The method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of the liquid phase layer, in the first stage, uses gaseous or solid chalcogenide compounds or chalcogenide elements as the sulfur source: hydrogen sulfide, sulfur powder, sodium sulfite, zinc sulfide, or di-tert-butyl disulfide, selenium particles, tellurium particles, or one or more of these; or the sulfur source is a liquid sulfur-containing solution: a sulfur solution of carbon disulfide; the carrier gas atmosphere is one or a mixture of two or more of nitrogen, argon, and hydrogen, and the carrier gas flow rate is 50-500 s·ccm.

[0016] In the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer, in the second stage, the molybdenum source for growing the multilayer molybdenum-based transition metal chalcogenide thin film comes from molybdenum atoms pre-stored in the solid pure gold layer in the first stage. The number of layers of the resulting uniform multilayer molybdenum-based transition metal chalcogenide thin film is controlled by parameters such as the selected non-metal type, the thickness of the liquid alloy, the growth temperature of the first layer of molybdenum-based transition metal chalcogenide thin film, the sulfur source supply method, and the cooling rate during the cooling process.

[0017] The method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of the liquid phase layer involves the following steps: After the preparation of the uniform multilayer molybdenum-based transition metal chalcogenide thin film, a polymer is coated onto its surface for protection using spin coating or blade coating. An electrochemical bubbling method is then used to transfer the uniform multilayer molybdenum-based transition metal chalcogenide thin film onto the target substrate. Subsequently, different types of organic solvents are used to remove the polymer protective layer, resulting in a clean, uniform multilayer molybdenum-based transition metal chalcogenide thin film with good device processability. The used alloy-gold composite substrate is then subjected to ultrasonic, annealing, and chemical treatments to restore its purity for repeated use.

[0018] The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide film on the surface of the liquid phase layer uses a polymer protective layer composed of one or more of polyethylene, polystyrene, polymethyl methacrylate and polypropylene, and the organic solvent used to clean the protective layer is composed of one or more of ketones, halogenated hydrocarbons, chlorinated hydrocarbons and aromatic hydrocarbons.

[0019] The design concept of this invention is:

[0020] This invention provides a method for preparing multilayer molybdenum-based transition metal chalcogenide thin films by constructing a liquid-solid composite substrate composed of an alloy / gold using physical vapor deposition (PVD) pretreatment. The solid gold layer has a certain molybdenum solubility, while the liquid layer has a low melting point and remains liquid at the growth temperature, serving as a diffusion channel for molybdenum. This substrate is applied to the chemical vapor deposition process, thereby developing a method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films. The thickness of the molybdenum-based transition metal chalcogenide thin film can be controlled by adjusting parameters such as the thickness of the liquid layer, the atmosphere, and the growth temperature. This method has advantages such as high efficiency, high controllability, and high-quality film samples, and can be used as a method for preparing uniform multilayer continuous molybdenum-based transition metal chalcogenide thin films.

[0021] This invention involves depositing a non-metallic thin film on a gold substrate (the only substrate that does not react with chalcogenides) using physical vapor deposition methods such as magnetron sputtering and thermal evaporation. A surface alloy is then prepared by annealing, forming a layer of gold over the non-metallic film. This alloy is required to have a low melting point, remaining liquid at the growth temperature (700–900°C) to form a liquid growth layer. A uniform, large-area, multilayered molybdenum-based transition metal chalcogenide film is then grown on the surface of this liquid layer using chemical vapor deposition. By adjusting the thickness of the surface alloy, the atmosphere, and the growth temperature, the number of layers in the molybdenum-based transition metal chalcogenide film can be controlled.

[0022] The advantages and beneficial effects of this invention are:

[0023] 1. This invention proposes a method combining physical vapor deposition and chemical vapor deposition to construct a clean and flat substrate. It combines gold with a certain amount of molybdenum and alloys formed by gold and different types of non-metals to form a liquid-solid composite substrate. The solid gold layer stores molybdenum, and the liquid alloy layer serves as a diffusion channel for molybdenum. This solves the problem of uneven molybdenum source supply in the preparation of molybdenum-based transition metal chalcogenides by traditional chemical vapor deposition methods, and achieves uniform and controllable number of layers in molybdenum-based transition metal chalcogenide films.

[0024] 2. The controllability of the number of layers in the molybdenum-based transition metal chalcogenide thin film of the present invention is specifically reflected in the following aspects: the length of the diffusion channel can be controlled by controlling the thickness of the non-metallic layer in physical vapor deposition, thereby controlling the molybdenum supply rate; the molybdenum supply can be adjusted by selecting the type of non-metal and the different diffusion rates of molybdenum by different alloys; at the same time, the controlled preparation of multilayer molybdenum-based transition metal chalcogenide thin films can be achieved by adjusting parameters such as gas flow rate, growth temperature, and cooling rate in the chemical vapor deposition process.

[0025] 3. The multilayer molybdenum-based transition metal chalcogenide thin films prepared by this invention have good crystallinity, which lays the foundation for the application of multilayer molybdenum-based transition metal chalcogenide thin films in nanoelectronic devices, optoelectronic devices, spintronic devices and other fields.

[0026] 4. The preparation process of this invention is simple, the substrate can be repeatedly recycled and reused, and it has the characteristics of low cost and scalability.

[0027] 5. The present invention can be used to prepare high-quality and uniformly thick multilayer molybdenum-based transition metal chalcogenide thin films, laying the foundation for the application of molybdenum-based transition metal chalcogenides in nanoelectronic devices, optoelectronic devices and other fields, and can be widely used in the field of chemical vapor deposition preparation of thin films. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process of the present invention, which utilizes physical vapor deposition technology to pre-treat the substrate, constructs a liquid-solid composite substrate, and then uses chemical vapor deposition technology to grow a molybdenum disulfide thin film on the liquid phase layer.

[0029] Figure 2 This is a schematic diagram of the apparatus used for magnetron sputtering pretreatment of pure gold substrates according to the present invention. In the figure, 21 represents the growth substrate, 22 represents the magnetron sputtering cathode, and a high-purity target is placed thereon.

[0030] Figure 3 This is a schematic diagram of the apparatus used in the annealing and chemical vapor deposition process of this invention. In the figure, 31 is the growth substrate, 32 is the molybdenum source, 33 is the sulfur source, 34 is the temperature control knob of the heating stage, 35 is the tube furnace, 36 is the quartz tube, 37 is the gas inlet, and 38 is the gas outlet.

[0031] Figure 4 This is a cross-sectional schematic diagram of the gold-silicon composite substrate produced by depositing silicon on a gold foil using magnetron sputtering on a substrate according to the present invention. In the figure, 41 is a pure-phase metal substrate, and 42 is a non-metallic thin film.

[0032] Figure 5 This is a schematic cross-sectional view of the gold-silicon composite substrate during the chemical vapor deposition process of this invention. After annealing, the upper non-metallic layer alloys with some pure phase metal to form a low-melting-point alloy layer. In the figure, 51 is the unalloyed pure phase metal, and 52 is the alloy layer.

[0033] Figure 6 This is a schematic diagram of the apparatus used for the thermal evaporation pretreatment of pure gold substrates according to the present invention. In the figure, 61 is the metal substrate, 62 is the evaporation boat, 63 is the non-metallic source, and 64 is the resistance heating device.

[0034] Figure 7 This figure shows the Raman spectra of molybdenum disulfide films prepared using different silicon film thicknesses according to the present invention. In the figure, the horizontal axis Raman Shift represents the Raman shift (cm). -1 The vertical axis Intensity represents the intensity (cnt). Detailed Implementation

[0035] In its specific implementation, this invention provides a method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on a liquid phase layer. First, the gold foil intended for chemical vapor deposition is pretreated. Then, a non-metallic thin film is deposited on the gold foil substrate using physical vapor deposition. Finally, a uniform multilayer molybdenum-based transition metal chalcogenide thin film is prepared using a chemical deposition process. Figure 1 This invention utilizes physical vapor deposition (PVD) technology to deposit a non-metallic thin film on a pre-treated, clean, pure-phase metal substrate, with a thickness ranging from 5 to 500 nm. Using this system, a liquid-solid composite substrate composed of a liquid alloy and gold is constructed. The gold foil substrate has a certain amount of dissolved molybdenum, ranging from 0.79 to 1.27 wt%, and the liquid alloy has a low melting point, remaining a liquid layer at the growth temperature. Using this composite substrate and during chemical vapor deposition, uniform multilayer molybdenum-based transition metal chalcogenide thin films are prepared by controlling parameters such as the thickness of the deposited non-metallic layer, the growth temperature, and the cooling rate. The number of layers ranges from 1 to 8, and the thickness ranges from 0.65 to 5.2 nm.

[0036] like Figure 3 As shown, the chemical vapor deposition system of the present invention mainly includes a growth substrate 31 located in the central heating zone of a tube furnace, a molybdenum source 32, a sulfur source 33 for the growth of transition metal sulfides, a heating stage temperature control knob 34 for controlling the heating of the sulfur source 33 to volatilize, a tube furnace 35, a quartz tube 36, a gas inlet 37, a gas outlet 38, and a gas mass flow controller (MFC). The quartz tube 36 is horizontally inserted into the tube furnace 35, and the growth substrate 31 is provided inside the quartz tube 36 corresponding to the central heating zone of the tube furnace 35. The molybdenum source 32 is located upstream of the tube furnace heating zone of the quartz tube 36, and the sulfur source 33 is located on the heating stage inside the quartz tube 36 outside the upstream of the tube furnace heating zone. The heating stage heats the sulfur source 33 by controlling the heating stage temperature control knob 34. Under the action of the gas mass flow controller (MFC), the carrier gas enters the quartz tube 36 of the tube furnace 35 from the gas inlet 37 and exits from the gas outlet 38.

[0037] To make the objectives, technical solutions, and effects of this invention clearer, the following will be combined with... Figure 1 A further detailed description of the present invention is provided below. It should be understood that the specific embodiments described below are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] Example 1

[0039] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0040] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0041] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0042] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0043] like Figure 2 As shown, magnetron sputtering was used. The cleaned growth substrate 21 was fixed on the sample disk in the magnetron sputtering working chamber. The sample disk was rotated at a speed of 20 rpm. After a silicon target with a purity of 99.999 wt% was placed at the magnetron sputtering cathode 22, the vacuum level of the magnetron sputtering chamber was evacuated to 5 × 10⁻⁶. -5 mbar is used to remove oxygen and other impurities from the chamber, followed by the introduction of argon gas at a flow rate of 50 s.ccm, maintaining a stable working pressure of 10. -2 The sputtering process used a DC power supply of mbar, with a sputtering voltage of 600V, a sputtering power of 25W, and a sputtering rate of 0.2 Å / s, to sputter a 500nm thick silicon film on the substrate. After sputtering, the power was turned off, and argon gas was introduced as a protective atmosphere. The sputtered gold-silicon composite substrate was removed only after the chamber cooled to room temperature to prevent oxidation at higher temperatures. Figure 4 As shown, this is a cross-sectional schematic diagram after the magnetron sputtering process in step S2. The pure phase metal substrate 41 (pure gold) is the gold foil processed in step S1. A non-metallic thin film 42 with a thickness of 500 nm is deposited on the pure phase metal substrate 41 by magnetron sputtering.

[0044] After sputtering, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed only after the chamber has cooled to room temperature to prevent oxidation at higher temperatures. The magnetron-sputtered substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at a flow rate of 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5 As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0045] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0046] like Figure 3As shown, the aforementioned gold-silicon composite substrate was placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum disulfide film at a set temperature. The composite substrate, placed in the central heating zone of a horizontal tube furnace, served as the growth substrate 31 for the molybdenum disulfide film. The molybdenum source 32 and sulfur source 33 were placed 10 cm and 20 cm away from the growth substrate 31, respectively. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0047] (1) The chemical vapor deposition process was carried out in an argon atmosphere with a flow rate of 50 s·ccm. The growth temperature was set at 850℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. At the same time, 99.99% pure sulfur powder was selected as the sulfur source, and 1g of the reagent was placed at position 33. A heating stage was placed under the sulfur source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 200℃.

[0048] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove the adsorbed impurities on the substrate surface. At the same time, the heating platform is turned on to raise the temperature of the heating platform to above the sulfur melting point. Liquid sulfur begins to volatilize and the growth step begins. After the 20-minute growth process is completed, the sulfur source temperature is reduced to 180°C. The horizontal tube furnace is set to slowly cool down at a rate of 10°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum disulfide film.

[0049] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0050] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread. The sample was then placed on a heating stage at 180°C for 10 minutes to cure the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to obtain a clean multilayer molybdenum disulfide film with a thickness of ~1.3 nm.

[0051] In this embodiment, the thin film prepared by this method is subjected to Raman spectroscopy testing. Figure 7 As shown, the Raman spectra of molybdenum disulfide films prepared by this invention using different silicon film thicknesses show that, regardless of the thickness of the silicon film, all samples exhibit Raman spectra. and The characteristic peaks corresponding to the two vibration modes (located at ~380cm) -1 With ~404cm -1 ),in, The peaks represent the relative vibrational modes between molybdenum and sulfur along the interlayer direction, while The peaks represent the relative vibrational modes of molybdenum-sulfur bonds along a direction perpendicular to the interlayer, while through... Peak and The peak position difference can be used to determine the number of layers in the molybdenum disulfide thin film: In this embodiment, the silicon layer thickness is 500 nm, corresponding to a 71 Raman spectrum. Peak and The peak position difference is approximately 25.4 cm. -1 This indicates that the molybdenum disulfide film grown in this embodiment is a double layer.

[0052] Example 2

[0053] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0054] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0055] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0056] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0057] like Figure 6As shown, unlike Example 1, a thermal evaporation method is used. The cleaned metal substrate 61 is fixed on a sample tray within the thermal evaporation working chamber. The sample tray is rotated at a speed of 15 rpm. A non-metallic source 63 (silicon-based target) with a purity of 99.999 wt% is loaded into the evaporation boat 62 below, and then heated and melted using a resistance heating device 64. The chamber vacuum is then evacuated to 5 × 10⁻⁶. -2 The pressure is set at mPa to remove oxygen and other impurities from the cavity and reduce particle collisions within the vacuum chamber. This deposition process uses a DC power supply with a heating power of 250W and a deposition rate of 0.2 Å / s to deposit a 500nm thick silicon film on the substrate.

[0058] After evaporation, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed after the chamber cools to room temperature to prevent oxidation at higher temperatures. The coated substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at a flow rate of 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5 As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0059] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0060] like Figure 3 As shown, the aforementioned gold-silicon composite substrate is placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum disulfide thin film at a set temperature. The composite substrate, placed in the central heating zone of a horizontal tube furnace, serves as the growth substrate 31 for the molybdenum disulfide thin film. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0061] (1) The chemical vapor deposition process was carried out in an argon atmosphere with a flow rate of 50 s·ccm. The growth temperature was set at 850℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. At the same time, 99.99% pure sulfur powder was selected as the sulfur source, and 1g of the reagent was placed at position 33. A heating stage was placed under the sulfur source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 200℃.

[0062] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove the adsorbed impurities on the substrate surface. At the same time, the heating platform is turned on to raise the temperature of the heating platform to above the sulfur melting point. Liquid sulfur begins to volatilize and the growth step begins. After the 20-minute growth process is completed, the sulfur source temperature is reduced to 180°C. The horizontal tube furnace is set to slowly cool down at a rate of 10°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum disulfide film.

[0063] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0064] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread. The sample was then placed on a heating stage at 180°C for 10 minutes to cure the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to obtain a clean, multilayered molybdenum disulfide film with a thickness of 1.3 nm.

[0065] Example 3

[0066] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0067] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0068] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0069] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0070] like Figure 2As shown, magnetron sputtering was used. The cleaned growth substrate 21 was fixed on the sample disk in the magnetron sputtering working chamber. The sample disk was rotated at a speed of 20 rpm. After a silicon target with a purity of 99.999 wt% was placed at the magnetron sputtering cathode 22, the vacuum level of the magnetron sputtering chamber was evacuated to 5 × 10⁻⁶. -5 mbar is used to remove oxygen and other impurities from the chamber, followed by the introduction of argon gas at a flow rate of 50 s.ccm, maintaining a stable working pressure of 10. -2 The sputtering process used a DC power supply with a sputtering voltage of 600V, a sputtering power of 25W, and a sputtering rate of 0.2 Å / s. Unlike Example 1, a 250nm thick silicon film was sputtered onto the substrate. After sputtering, the power was turned off, and argon gas was introduced as a protective atmosphere. The sputtered gold-silicon composite substrate was removed after the chamber cooled to room temperature to prevent oxidation at higher temperatures.

[0071] After sputtering, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed only after the chamber has cooled to room temperature to prevent oxidation at higher temperatures. The magnetron-sputtered substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at a flow rate of 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5 As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0072] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0073] like Figure 3 As shown, the aforementioned gold-silicon composite substrate is placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum disulfide thin film at a set temperature. The composite substrate placed in the central heating zone of a horizontal tube furnace serves as the growth substrate 31 for the molybdenum disulfide thin film. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0074] (1) The chemical vapor deposition process was carried out in an argon atmosphere with a flow rate of 50 s·ccm. The growth temperature was set at 850℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. At the same time, 99.99% pure sulfur powder was selected as the sulfur source, and 1g of the reagent was placed at position 33. A heating stage was placed under the sulfur source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 200℃.

[0075] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove adsorbed impurities on the substrate surface. At the same time, the heating platform is turned on to raise the temperature of the heating platform to above the sulfur melting point. Liquid sulfur begins to volatilize and the growth step begins. After the 20-minute growth process is completed, the sulfur source temperature is reduced to 180°C. The horizontal tube furnace is set to slowly cool down at a rate of 5°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum disulfide film.

[0076] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0077] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread. The sample was then placed on a heating stage at 180°C and baked for 10 minutes to complete the curing of the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to finally obtain a clean multilayer molybdenum disulfide film with a thickness of ~2 nm.

[0078] In this embodiment, the thin film prepared by this method is subjected to Raman spectroscopy testing. Figure 7 As shown, when the silicon layer thickness is 250 nm, the corresponding 72 Raman spectrum is... Peak and The peak position difference is approximately 27.3 cm. -1 This indicates that the molybdenum disulfide film grown in this embodiment is three-layered. The reduction in the thickness of the silicon layer reduces the length of the diffusion channel, decreases the diffusion time of molybdenum atoms, and increases the number of molybdenum disulfide film layers obtained.

[0079] Example 4

[0080] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0081] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0082] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0083] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0084] like Figure 2 As shown, magnetron sputtering was used. The cleaned growth substrate 21 was fixed on the sample disk in the magnetron sputtering working chamber. The sample disk was rotated at a speed of 20 rpm. After a silicon target with a purity of 99.999 wt% was placed at the magnetron sputtering cathode 22, the vacuum level of the magnetron sputtering chamber was evacuated to 5 × 10⁻⁶. -5 mbar is used to remove oxygen and other impurities from the chamber, followed by the introduction of argon gas at a flow rate of 50 s.ccm, maintaining a stable working pressure of 10. -2 The sputtering process used a DC power supply of mbar, with a sputtering voltage of 600V, a sputtering power of 25W, and a sputtering rate of 0.2 Å / s. Unlike Example 1, a 100nm thick silicon film was sputtered on the substrate. After sputtering, the power was turned off, and argon gas was introduced as a protective atmosphere. The sputtered gold-silicon composite substrate was removed after the chamber cooled to room temperature to prevent oxidation at higher temperatures. Figure 4 As shown, this is a cross-sectional schematic diagram after the magnetron sputtering process in step S2. The pure phase metal substrate 41 is the gold foil processed in step S1, and a non-metallic thin film 42 is deposited on the pure phase metal substrate 41 by magnetron sputtering.

[0085] After sputtering, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed only after the chamber has cooled to room temperature to prevent oxidation at higher temperatures. The magnetron-sputtered substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5 As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0086] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0087] like Figure 3 As shown, the aforementioned gold-silicon composite substrate is placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum disulfide thin film at a set temperature. The composite substrate placed in the central heating zone of a horizontal tube furnace serves as the growth substrate 31 for the molybdenum disulfide thin film. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0088] (1) The chemical vapor deposition process was carried out entirely in an argon atmosphere with a flow rate of 50 s·ccm. Unlike Example 1, the growth temperature was set to 800℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. At the same time, 99.99% pure sulfur powder was selected as the sulfur source, and 1g of the reagent was placed at position 33. A heating stage was placed under the sulfur source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 200℃.

[0089] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove adsorbed impurities on the substrate surface. At the same time, the heating platform is turned on to raise the temperature of the heating platform to above the sulfur melting point. Liquid sulfur begins to volatilize and the growth step begins. After the 20-minute growth process is completed, the sulfur source temperature is reduced to 180°C. The horizontal tube furnace is set to slowly cool down at a rate of 5°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum disulfide film.

[0090] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0091] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread. The sample was then placed on a heating stage at 180°C and baked for 10 minutes to complete the curing of the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to finally obtain a clean multilayer molybdenum disulfide film with a thickness of ~2.6 nm.

[0092] In this embodiment, the thin film prepared by this method is subjected to Raman spectroscopy testing. Figure 7 As shown, when the silicon layer thickness is 100 nm, the corresponding Raman spectrum is 73. Peak and The peak position difference is approximately 29.7 cm. -1 This indicates that the molybdenum disulfide film grown in this embodiment has four layers. The further reduction in the thickness of the silicon layer reduces the length of the diffusion channel, decreases the diffusion time of molybdenum atoms, and increases the number of molybdenum disulfide film layers obtained.

[0093] Example 5

[0094] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0095] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0096] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0097] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0098] like Figure 2As shown, magnetron sputtering was used. The cleaned growth substrate 21 was fixed on the sample disk in the magnetron sputtering working chamber. The sample disk was rotated at a speed of 20 rpm. After a silicon target with a purity of 99.999 wt% was placed at the magnetron sputtering cathode 22, the vacuum level of the magnetron sputtering chamber was evacuated to 5 × 10⁻⁶. -5 mbar is used to remove oxygen and other impurities from the chamber, followed by the introduction of argon gas at a flow rate of 50 s.ccm, maintaining a stable working pressure of 10. -2 The sputtering process used a DC power supply of mbar, with a sputtering voltage of 600V, a sputtering power of 25W, and a sputtering rate of 0.2 Å / s. Unlike Example 1, a 50nm thick silicon film was sputtered on the substrate. After sputtering, the power was turned off, and argon gas was introduced as a protective atmosphere. The sputtered gold-silicon composite substrate was removed after the chamber cooled to room temperature to prevent oxidation at higher temperatures. Figure 4 As shown, this is a cross-sectional schematic diagram after the magnetron sputtering process in step S2. The pure phase metal substrate 41 is the gold foil processed in step S1, and a non-metallic thin film 42 is deposited on the pure phase metal substrate 41 by magnetron sputtering.

[0099] After sputtering, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed only after the chamber has cooled to room temperature to prevent oxidation at higher temperatures. The magnetron-sputtered substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at a flow rate of 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5 As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0100] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0101] like Figure 3 As shown, the aforementioned gold-silicon composite substrate is placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum disulfide thin film at a set temperature. The composite substrate placed in the central heating zone of a horizontal tube furnace serves as the growth substrate 31 for the molybdenum disulfide thin film. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0102] (1) The chemical vapor deposition process was carried out entirely in an argon atmosphere with a flow rate of 50 s·ccm. Unlike Example 1, the growth temperature was set to 800℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. At the same time, 99.99% pure sulfur powder was selected as the sulfur source, and 1g of the reagent was placed at position 33. A heating stage was placed under the sulfur source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 200℃.

[0103] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove adsorbed impurities on the substrate surface. At the same time, the heating platform is turned on to raise the temperature of the heating platform to above the sulfur melting point. Liquid sulfur begins to volatilize and the growth step begins. After the 20-minute growth process is completed, the sulfur source temperature is reduced to 180°C. The horizontal tube furnace is set to slowly cool down at a rate of 5°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum disulfide film.

[0104] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0105] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate (PMMA) ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread. The sample was then placed on a heating stage at 180°C and baked for 10 minutes to complete the curing of the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to finally obtain a clean multilayer molybdenum disulfide film with a thickness of ~2.6 nm.

[0106] In this embodiment, the thin film prepared by this method is subjected to Raman spectroscopy testing. Figure 7 As shown, when the silicon layer thickness is 50 nm, the corresponding Raman spectrum is 74. Peak and The peak position difference is approximately 30.1 cm. -1 This indicates that the molybdenum disulfide film grown in this embodiment consists of four layers.

[0107] Example 6

[0108] like Figure 1 As shown, the method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of the liquid phase layer in this embodiment is as follows:

[0109] S1: Pretreatment of gold foil intended for use in chemical vapor deposition process.

[0110] A pure metal substrate (100 μm thick, 10 mm long, 10 mm wide, 99.95 wt% pure) was ultrasonicated for 1 hour each with 1 mol / L nitric acid, acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun to remove surface chemical residues. The ultrasonically treated substrate was then heated to 1000°C in air and annealed for 10 hours to remove surface impurities as much as possible and improve the surface smoothness.

[0111] S2: A silicon thin film is deposited on a gold foil substrate using physical vapor deposition to construct a liquid-solid composite substrate composed of alloys and metals.

[0112] like Figure 2 As shown, magnetron sputtering was used. The cleaned growth substrate 21 was fixed on the sample disk in the magnetron sputtering working chamber. The sample disk was rotated at a speed of 20 rpm. After a silicon target with a purity of 99.999 wt% was placed at the magnetron sputtering cathode 22, the vacuum level of the magnetron sputtering chamber was evacuated to 5 × 10⁻⁶. -5 mbar is used to remove oxygen and other impurities from the chamber, followed by the introduction of argon gas at a flow rate of 50 s.ccm, maintaining a stable working pressure of 10. -2 The sputtering process used a DC power supply of mbar, with a sputtering voltage of 600V, a sputtering power of 25W, and a sputtering rate of 0.2 Å / s, to sputter a 5nm thick silicon film on the substrate. After sputtering, the power was turned off, and argon gas was introduced as a protective atmosphere. The sputtered gold-silicon composite substrate was removed only after the chamber cooled to room temperature to prevent oxidation at higher temperatures. Figure 4 As shown, this is a cross-sectional schematic diagram after the magnetron sputtering process in step S2. The pure phase metal substrate 41 is the gold foil processed in step S1, and a non-metallic thin film 42 is deposited on the pure phase metal substrate 41 by magnetron sputtering.

[0113] After sputtering, the power is turned off, and argon gas is introduced as a protective atmosphere. The sputtered gold-silicon composite substrate is removed only after the chamber has cooled to room temperature to prevent oxidation at higher temperatures. The magnetron-sputtered substrate is then placed in the central heating zone of a horizontal tube furnace and heated to 1000°C in a hydrogen reducing atmosphere at a flow rate of 500 s·ccm, and held at that temperature for 10 hours to obtain a composite substrate composed of an alloy and a pure-phase metal. Figure 5As shown, after annealing, the upper silicon and gold are annealed to form a low-melting-point alloy layer 52, and the lower layer is an unalloyed pure phase metal 51.

[0114] S3: Molybdenum disulfide thin films were prepared using a chemical deposition process.

[0115] like Figure 3 As shown, the aforementioned gold-silicon composite substrate is placed in a sealed quartz tube within a chemical vapor deposition system to grow a molybdenum diselenide thin film at a set temperature. The composite substrate, placed in the central heating zone of a horizontal tube furnace, serves as the growth substrate 31 for the molybdenum diselenide thin film. The liquid phase layer significantly improves the surface smoothness of the substrate and the uniformity and speed of precursor diffusion on the substrate surface, ultimately enhancing the sample quality. The specific steps and parameters in this process are as follows:

[0116] (1) The chemical vapor deposition process was carried out in an argon atmosphere with a flow rate of 50 s·ccm. The growth temperature was set at 800℃, the heating rate was 30℃ / min, and the growth time was 20min. In this experiment, 99.99% pure molybdenum oxide powder was selected as the molybdenum source, and 1g of the reagent was placed at position 32, where the temperature was about 300℃. Unlike Example 1, this experiment selected 99.99% pure selenium particles as the selenium source, and 1g of the reagent was placed at position 33. A heating stage was placed under the selenium source to heat the sulfur powder to generate sulfur vapor, which was supplied for growth. The control knob 34 was used to set the temperature of the heating stage to 350℃.

[0117] (2) After the furnace body is heated to the growth temperature, it is kept at the temperature for 10 minutes to remove adsorbed impurities on the substrate surface. At the same time, the heating stage is turned on to raise the temperature of the heating stage to above the melting point of selenium. Liquid selenium begins to volatilize, and the growth step begins. After the 20-minute growth process is completed, the selenium source temperature is reduced to 330°C. The horizontal tube furnace is set to slowly cool down at a rate of 5°C / minute. The temperature is reduced to 750°C, so that molybdenum atoms slowly precipitate from the solid layer, diffuse through the liquid layer to the surface, and react with sulfur vapor to form a multilayer molybdenum diselenide film.

[0118] (3) After the growth process is completed, maintain an argon flow rate of 50 s.ccm, turn off the heating stage and tube furnace, and take out the substrate after it has cooled naturally to room temperature with the furnace to prevent the rapid cooling process from affecting the sample quality.

[0119] (4) A protective layer covering the sample surface was prepared by spin coating using a 4 wt% polymethyl methacrylate ethyl lactate solution. The polymer mixture was dropped onto the sample surface, and the sample was rotated at 2000 rpm to ensure the protective layer was evenly spread on the sample surface. The sample was then placed on a heating stage at 180°C and baked for 10 minutes to complete the curing of the polymer protective layer. The sample covered with the protective layer was placed as the cathode in a 1 mol / L sodium hydroxide aqueous solution, and a constant current of 0.3 A was passed through it. The hydrogen gas generated at the cathode could completely peel the sample, along with the protective layer, from the substrate and transfer it to the desired substrate. The polymer protective layer could be dissolved in hot acetone to finally obtain a clean multilayer molybdenum diselenide film with a thickness of ~0.7 nm.

[0120] The results show that this invention utilizes magnetron sputtering to introduce silicon to construct an alloy-gold composite substrate. Through alloying at the growth temperature, a liquid phase layer is formed, significantly improving the diffusion rate and uniformity of the precursor on the substrate surface compared to a solid substrate. This ultimately yields a uniform, high-quality molybdenum-based transition metal chalcogenide thin film. This invention successfully combines physical vapor deposition (PVD) with chemical vapor deposition (CVD), solving the problem of low controllability in purely CVD methods. It improves the controllability and repeatability of the method, laying the foundation for the application of molybdenum-based transition metal chalcogenide thin films in optics, electronics, and other fields. It also provides a new approach to thin film fabrication and holds promise for application in the preparation of other two-dimensional material thin films.

Claims

1. A method for preparing uniform multilayer molybdenum-based transition metal chalcogenide thin films on the surface of a liquid phase layer, characterized in that, After cleaning and annealing at 800–1200 °C for 5–15 hours, a thin film with a thickness of 25–500 nm, capable of forming a low-melting-point alloy with gold, is deposited on the gold substrate surface via physical vapor deposition. The film composition is one or more of silicon, germanium, gallium, and antimony. After a second annealing, a liquid-solid composite substrate consisting of a liquid alloy and gold is constructed at high temperatures. The thin film composition capable of forming a low-melting-point alloy with gold is deposited on the clean gold substrate surface via physical vapor deposition using magnetron sputtering or thermal evaporation. To construct the liquid alloy surface layer at the growth temperature, the substrate with the deposited film composition is annealed at 900–1100 °C in hydrogen or a hydrogen-containing gas mixture, wherein the hydrogen volume ratio is not less than 5%, the gas flow rate is 500–1000 sccm, and the annealing time is 0.5–10 h. The solid-phase structure constructed from gold has the characteristics of high melting point, non-reaction with sulfur, and a certain molybdenum solubility, ranging from 0.79 to 1.

27. The liquid alloy layer, at a growth temperature of 800-900℃, is liquid and covers the surface of the solid structure of the gold substrate, serving as a diffusion layer for molybdenum. Using chemical vapor deposition, a structure of liquid alloy encapsulating solid gold substrate is formed at the growth temperature. By adjusting the thickness of the liquid layer and the growth temperature and atmosphere parameters, and utilizing the controllable diffusion of molybdenum atoms in the liquid layer, a uniform multilayer molybdenum-based transition metal chalcogenide film is prepared. The process for preparing multilayer molybdenum-based transition metal chalcogenide thin films on the surface of a liquid phase layer is as follows: The first stage: Using a liquid-solid composite substrate composed of alloy and gold as the growth substrate, gaseous, liquid or solid chalcogenide sources are selected. At the growth temperature, a liquid-solid stacked structure is constructed with a liquid alloy layer covering a solid pure gold layer. With the assistance of a carrier gas, a monolayer molybdenum-based transition metal chalcogenide film is first grown on the surface of the liquid alloy. At the same time, some molybdenum atoms pass through the liquid alloy layer and are pre-stored in the gold substrate. The second stage involves cooling the reaction temperature to 750°C at a rate of 5°C / min or 10°C / min, causing the molybdenum atoms pre-stored in the solid gold matrix to be released and precipitated. These atoms then diffuse controllably through the liquid alloy layer to the space between the liquid surface and the monolayer molybdenum-based transition metal chalcogenide, where they react with the chalcogen source diffused into this gap, ultimately forming a multilayer molybdenum-based transition metal chalcogenide film with a uniform number of layers.

2. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, To form a stable liquid-solid structure at the growth temperature, a thin film capable of forming a low-melting-point alloy with gold is prepared by physical vapor deposition and coated on the upper surface of a gold substrate.

3. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, In the alloy and gold substrate constituting the liquid-solid composite substrate, the gold has catalytic activity, a purity greater than 99.9 wt%, and a thickness greater than 50 micrometers.

4. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, In the liquid-solid composite substrate, the alloy and the gold substrate are formed by the combination of gold with one or more elements selected from silicon, germanium, gallium and antimony at high temperature, and the resulting alloy is in a liquid state at the growth temperature.

5. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, In the first stage, the chalcogen source is selected from gaseous or solid chalcogen compounds or chalcogen elements: hydrogen sulfide, sulfur powder, sodium sulfite, zinc sulfide or di-tert-butyl disulfide, selenium particles, tellurium particles or one or more of these, or the chalcogen source is a liquid sulfur-containing solution: a sulfur solution of carbon disulfide; the carrier gas atmosphere is a mixture of one or more of nitrogen, argon, and hydrogen, and the carrier gas flow rate is 50~500 sccm.

6. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, In the second stage, the molybdenum source for growing the multilayer molybdenum-based transition metal chalcogenide film comes from the molybdenum atoms pre-stored in the solid pure gold layer in the first stage. The number of layers of the resulting uniform multilayer molybdenum-based transition metal chalcogenide film is controlled by the selected film composition, the thickness of the liquid alloy, the growth temperature of the first layer of molybdenum-based transition metal chalcogenide film, the chalcogen source supply method, and the cooling rate parameters during the cooling process.

7. The method for preparing a uniform multilayer molybdenum-based transition metal chalcogenide thin film on the surface of a liquid phase layer according to claim 1, characterized in that, After the preparation of a uniform multilayer molybdenum-based transition metal chalcogenide film, a polymer is coated onto its surface for protection using spin coating or blade coating. The uniform multilayer molybdenum-based transition metal chalcogenide film is then transferred to the target substrate using an electrochemical bubbling method. Subsequently, an organic solvent is used to remove the polymer protective layer, resulting in a clean, uniform multilayer molybdenum-based transition metal chalcogenide film with good device processability. The selected polymer protective layer is composed of one or more of polyethylene, polystyrene, polymethyl methacrylate, and polypropylene. The organic solvent used to clean the protective layer is composed of one or more of ketones, halogenated hydrocarbons, chlorinated hydrocarbons, and aromatic hydrocarbons.

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