A method for growing two-dimensional materials based on counterflow non-metal source supply

Abstract

The application discloses a two-dimensional material growth method based on countercurrent non-metal source supply, and belongs to the technical field of two-dimensional materials. In the preparation, a non-metal source is placed in a single-port quartz test tube and arranged downstream of a tube furnace by using countercurrent supply of a chemical vapor deposition system. After the non-metal source is gasified at high temperature, the non-metal source is diffused to the surface of a substrate by using a concentration gradient, and the flow rate of a carrier gas can be regulated to regulate the non-metal source gas phase concentration on the surface of the substrate. Compared with a conventional chemical vapor deposition method, the method solves the problems of surface "deactivation" of a metal source and substrate pollution caused by diffusion of the non-metal source to the metal source and the substrate before the growth process. The preparation method provided by the application has strong controllability, the morphology, domain size and optical quality of the obtained two-dimensional transition metal chalcogenide are uniform, and the two-dimensional transition metal chalcogenide has excellent optical and electrical properties and wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional material preparation and semiconductor material technology, specifically relating to a method for preparing two-dimensional transition metal chalcogenides based on countercurrent non-metallic source supply and its dedicated chemical vapor deposition apparatus. Background Technology

[0002] Two-dimensional transition metal chalcogenides, represented by MS2 and WSe2, have shown great application potential in next-generation integrated circuits, flexible electronic devices, and photoelectric detection due to their atomic-level thickness, high carrier mobility, and tunable direct bandgap. Achieving high-quality, large-area, and uniform controllable growth of transition metal chalcogenides is a key prerequisite for their transition from laboratory research to industrial application.

[0003] Currently, chemical vapor deposition (CVD) has become the mainstream technology for preparing large-area two-dimensional transition metal chalcogenides due to its potential for large-scale preparation. In typical CVD processes, metal oxides (such as MoO3 and WO3) and non-metallic powders (such as sulfur powder and selenium powder) are usually used as the reaction source. However, traditional supply methods often employ "co-current transport," where the non-metallic source is located upstream, and the carrier gas is directly blown to the substrate and metal source downstream. This approach has the following problems: (1) Side reaction problems during the heating stage: The sublimation temperature of non-metallic sources (such as sulfur powder / selenium powder) is usually much lower than the reaction temperature of metal sources. During the heating stage, a large amount of gaseous non-metals arrive at the surface of the metal source with the carrier gas in advance, causing the metal source to undergo surface sulfidation / selenization before reaching the ideal volatilization temperature, forming a dense passivation shell, which severely inhibits the effective supply of subsequent metal precursors. At the same time, the reaction between the metal source and the non-metallic source near the substrate surface during the low-temperature stage leads to excessively dense nucleation, making it difficult to grow large-area single crystals.

[0004] (2) Spatial growth non-uniformity: In the downstream system, the precursor concentration is significantly consumed along the gas flow direction. This leads to an imbalance in the ratio of metal / non-metal source components at different locations on the substrate, which easily results in excessively dense nucleation upstream of the substrate, limited downstream domain size, or uneven number of layers. The grain morphology and size change significantly along the gas flow direction.

[0005] (3) The timing of non-metallic source supply is difficult to control precisely: Traditional methods can only control the concentration of non-metallic source by adjusting the heating temperature of non-metallic source. However, due to the thermal inertia in the tube and the dynamic changes in the concentration of metal source, it is difficult to achieve dynamic matching between the supply rate of gaseous non-metallic source and metal source. This usually leads to the presence of sulfur vacancy defects in crystal, affecting its electrical properties.

[0006] To address the aforementioned issues with co-current layouts, improved counter-current layout solutions have emerged in the prior art. For example, CN107385508B discloses a method for preparing monolayer molybdenum disulfide thin films by reusing molybdenum trioxide. In this method, sulfur powder (a non-metallic source) is placed downstream of the carrier gas flow, while MoO3 powder (a metallic source) and a sapphire substrate are placed upstream. By adjusting the carrier gas flow rate, the concentration of sulfur vapor in the temperature zone is controlled, thereby preventing MoO3 sulfidation poisoning and reusing the metallic source. Furthermore, it can grow MoS2 thin films with grain sizes exceeding 100 μm. This scheme effectively alleviates the pre-sulfurization problem of the metal source through counter-current layout, which is an important improvement over the traditional co-current process. However, it still has obvious technical limitations: First, the carrier gas flow rate uses only a single constant value, which cannot achieve on-demand supply of non-metallic sources. During the heating stage, there may still be slight pre-reactions where non-metallic source vapor diffuses to the surface of the metal source in advance. During the cooling stage, it cannot adapt to the change in the amount of metal source volatilization, which can easily cause an imbalance in precursor concentration matching. Second, the non-metallic source is simply placed in an ordinary ceramic boat without a directional constraint structure. The diffusion direction of non-metallic vapor is random, which can easily lead to uneven distribution of precursor concentration field on the substrate surface, affecting the large-area uniformity of the film. Third, this scheme is only designed for the MoS2 single system and does not consider the compatibility with other transition metal chalcogenides such as selenides, resulting in poor process versatility.

[0007] In summary, neither traditional co-current transport processes nor existing improved schemes based on counter-current layouts have fundamentally solved the core technical challenges in the dual-source chemical vapor deposition (CVD) preparation of two-dimensional transition metal chalcogenides: the concentration of the non-metallic source vapor phase cannot be dynamically and precisely controlled throughout the entire growth stage; the lack of directional constraint on the diffusion of non-metallic source vapors leads to uneven substrate concentration fields; and some solutions are only applicable to single systems with stringent process conditions, failing to meet the demands for high-quality, large-area, and uniform large-scale preparation. Therefore, designing a layout structure suitable for the separate placement of dual reaction sources, achieving directional diffusion of the non-metallic source and on-demand supply and precise timing control throughout the entire growth stage, fundamentally avoiding pre-reactions during the heating stage, maintaining a uniform distribution of the precursor concentration field on the substrate surface, and simultaneously improving the versatility and scalability of the process are key technical challenges that urgently need to be addressed for the large-scale preparation of high-quality two-dimensional transition metal chalcogenides. Summary of the Invention

[0008] This invention aims to solve the technical problems in the existing chemical vapor deposition (CVD) growth of two-dimensional transition metal chalcogenides, such as metal source surface "deactivation," uncontrollable nucleation density, and poor crystal quality caused by the asynchronous supply of non-metallic and metallic sources. To address these problems, this invention proposes a method and apparatus for growing two-dimensional transition metal chalcogenides based on countercurrent non-metallic source supply. By precisely controlling the carrier gas flow rate, accurate dynamic control of the timing and concentration of non-metallic source supply is achieved.

[0009] To achieve the above objectives, the present invention first provides a two-dimensional material growth method based on countercurrent non-metallic source supply, comprising the following steps: (1) Place the transition metal source and substrate in the central heating zone of the tube furnace, and place the solid non-metal source in a single-port container with the opening facing upstream, and place it in the non-metal source heating zone downstream of the airflow direction of the tube furnace. (2) Continuously introduce protective carrier gas into the tubular furnace, start the tubular furnace heating program, divide the growth process into a heating stage, an isothermal growth stage and a cooling stage, regulate the gas phase concentration of the non-metallic source by adjusting the flow rate of the carrier gas, and the flow rate of the carrier gas in each stage satisfies: the flow rate in the heating stage ≥ the flow rate in the cooling stage > the flow rate in the isothermal growth stage. After the cooling stage ends, keep the carrier gas continuously introduced to cool the tubular furnace to room temperature and obtain a two-dimensional transition metal chalcogenide.

[0010] In one embodiment of the present invention, the transition metal source in step (1) is a molybdenum source or a tungsten source, wherein the molybdenum source includes at least one of molybdenum oxide, elemental molybdenum, molybdenum halide and molybdate; and the tungsten source includes at least one of tungsten oxide, elemental tungsten, tungsten halide and tungstate.

[0011] In one embodiment of the present invention, in step (1), the substrate includes at least one of silicon / silicon dioxide, sapphire, fused glass, and mica.

[0012] In one embodiment of the present invention, in step (1), the solid non-metallic source includes any one of sulfur powder, selenium powder, and tellurium powder.

[0013] In one embodiment of the present invention, in step (1), the transition metal source is preferably placed between two substrates, and more preferably between two substrates bonded together.

[0014] In one embodiment of the present invention, in step (1), the transition metal source is placed inside the bonded glass substrate. Specifically, the transition metal source is uniformly laid on the surface of the first glass substrate, dried, covered with the second glass substrate, and placed in a muffle furnace for heat treatment to obtain bonded glass containing the transition metal source. The heat treatment is performed at 680~720℃ for 30~60min, and the heating rate during the heat treatment is 10~30℃ / min.

[0015] This invention achieves uniform supply of a transition metal source by bonding it to the interior of a glass substrate and diffusing the metal source to the glass surface at high temperature. Simultaneously, the metal and non-metal sources are supplied via different pathways, thus confining the growth of transition metal chalcogenides to the substrate surface and preventing gas-phase reactions and byproduct formation. This method facilitates the growth of uniformly distributed, high-quality two-dimensional materials on centimeter-scale substrate surfaces.

[0016] In one embodiment of the present invention, in step (2), the protective carrier gas includes at least one of nitrogen, argon, nitrogen / hydrogen mixture, and argon / hydrogen mixture.

[0017] In one embodiment of the present invention, in step (2), after starting the tubular furnace heating program, the heating temperature of the non-metallic source heating zone is 100~500℃, and the specific heating temperature range is determined according to the type of non-metallic source. For example, the heating temperature of the sulfur source is 100~250℃, preferably 150~210℃; the heating temperature of the selenium source is 200~350℃; and the heating temperature of the tellurium source is 400~500℃.

[0018] In one embodiment of the present invention, in step (2), after the heating program is started, the heating rate of the sulfur source is 15~55 ℃ / min, preferably 35~45 ℃ / min.

[0019] In one embodiment of the present invention, in step (2), after the heating program is started, the heating temperature of the central heating zone during the constant temperature stage is 500~1200 ℃, preferably 600~1100 ℃. When the transition metal source is sodium molybdate, the heating temperature is 650~800 ℃; when the transition metal source is sodium tungstate, the heating temperature is 750~900 ℃. In one embodiment of the present invention, in step (2), the heating rate of the central heating zone during the heating stage is 15~50 ℃ / min, preferably 25~45 ℃ / min. The cooling stage is natural cooling, and the final temperature of the cooling stage is 20-60 ℃.

[0020] In one embodiment of the present invention, in step (2), the rate of introduction of protective carrier gas during the heating stage is 30-100 sccm; the rate of introduction of protective gas during the isothermal stage is 3-10 sccm; and the rate of introduction of protective gas during the cooling stage is 10-100 sccm.

[0021] In one embodiment of the present invention, in step (2), the heat preservation time of the heat preservation stage is 2 to 60 minutes, preferably 10 to 30 minutes.

[0022] In one embodiment of the present invention, in step (2), the pressure in the tubular furnace is 760 torr.

[0023] In one embodiment of the present invention, the molar ratio of the transition metal source to the sulfur source is 1:3 to 1:100.

[0024] This invention provides a chemical vapor deposition apparatus with a countercurrent non-metallic source supply, comprising a reaction chamber, a substrate located in a central heating zone, and a non-metallic source located in a downstream heating zone. A single-port container (such as a single-port quartz tube) with its opening facing upstream is placed within the non-metallic source heating zone. This structure, opposite to the direction of the carrier gas, constitutes a diffusion resistance field.

[0025] This invention relates to a method for growing two-dimensional transition metal chalcogenides using a countercurrent non-metallic source. The core feature is that the non-metallic source is placed in a container with its opening facing upstream, downstream of a chemical vapor deposition tube furnace. The concentration gradient generated after the non-metallic source vaporizes drives its diffusion countercurrently to the substrate surface located in the middle downstream. The diffusion rate of the non-metallic source is controlled by adjusting the carrier gas flow rate at different growth stages, utilizing the carrier gas dynamic pressure resistance. Specifically, the carrier gas flow rate during the heating stage ≥ the carrier gas flow rate during the cooling stage > the carrier gas flow rate during the isothermal stage. This growth method has the following advantages: during the heating stage, the non-metallic source sublimates. With a carrier gas flow rate of 30-100 sccm, the high-flow-rate carrier gas effectively prevents the low-temperature sublimated non-metallic vapor from entering the reaction zone, preventing premature sulfidation / selenization of the metal source surface. During the isothermal stage, the carrier gas flow rate is reduced to 3-10 sccm to decrease carrier gas resistance, allowing the non-metallic source to smoothly diffuse countercurrently to the substrate under the drive of the concentration gradient to participate in growth, providing sufficient non-metallic source for the reaction. Simultaneously, due to the unidirectional opening, the non-metallic source is consumed slowly, allowing for a continuous supply over a longer period. During the cooling stage, the carrier gas flow rate is 10-100 sccm, with a moderate increase in flow rate to supply a small amount of sulfur vapor while preventing secondary deposition or contamination during cooling, thus avoiding the formation of sulfur vacancies. This method effectively overcomes the sulfur source supply problem in existing technologies by avoiding premature nucleation at low temperatures while ensuring sufficient sulfidation reaction at high temperatures. It improves the quality of two-dimensional crystals such as molybdenum disulfide grown by chemical vapor deposition and makes the film morphology more uniform and controllable.

[0026] In a specific embodiment of the present invention, the preparation process of the two-dimensional transition metal chalcogenide adopts a segmented control strategy, and the specific steps are as follows: (1) A transition metal source (such as a molybdenum source or a tungsten source) is uniformly deposited on the surface of the bottom glass substrate (thickness 1.0–5.0 mm), and the loading of the transition metal source is controlled to be 0.2–2 mg / cm². After being completely dried in a forced-air drying oven, a thin upper glass substrate of the same size (thickness 0.01–0.2 mm) is placed on top. The structure is then placed in a muffle furnace and heat-treated at 100–720 °C for 60 min (heating rate 40 °C / min) to melt and bond the two glass substrates together, forming a composite substrate containing the metal source.

[0027] (2) The bonded glass substrate prepared in step 1 is placed in the central heating zone (substrate heating zone) of the tube furnace, serving as both the substrate and the transition metal source. The solid non-metallic source (such as sulfur powder, selenium powder, tellurium powder, etc.) is placed in a single-port container with the opening facing upstream, and positioned downstream of the airflow direction of the tube furnace (non-metallic source heating zone). With this arrangement, the non-metallic source flows in the opposite direction to the carrier gas, forming the basis for countercurrent diffusion.

[0028] (3) During growth, a protective carrier gas is first introduced into the tube. During the heating stage, the substrate area is heated to 600–800 °C at a rate of 25–45 °C / min. During this stage, the carrier gas flow rate is set to 30–100 sccm. The dynamic pressure generated by the high flow rate effectively blocks the vapor generated by the downstream non-metallic source at low temperature, preventing it from prematurely diffusing backflow into the substrate area and avoiding passivation of the metal source surface and excessive nucleation. During the isothermal growth stage, when the substrate reaches the target growth temperature, the carrier gas flow rate is reduced to 3–10 sccm. At this time, the carrier gas resistance decreases, and the non-metallic source vapor, driven by the concentration gradient, diffuses backflow into the surface of the bonded glass substrate, where it undergoes a chemical vapor deposition reaction with the heat-dissolved and precipitated transition metal source. This state is maintained for 10–60 min, during which a stable supply of non-metallic components is maintained by a low flow rate. During the cooling phase after the reaction, the carrier gas flow rate is adjusted back to 10-100 sccm, and the system is allowed to cool naturally. The appropriately increased carrier gas flow rate can remove residual vapor and prevent unnecessary byproducts from being generated during the cooling process. At the same time, a small amount of vapor concentration helps to repair sulfur vacancies.

[0029] Beneficial effects: (1) This invention places the transition metal source and the substrate in the central heating zone of a tube furnace, and the solid non-metal source in a single-port container with the opening facing upstream. Simultaneously, it regulates the flow rate of the carrier gas to fundamentally suppress the premature diffusion of non-metal source vapor to the metal source surface, preventing the formation of a passivation shell on the metal source and ensuring an effective supply of the metal precursor. This also avoids the problem of excessively dense substrate nucleation caused by low-temperature non-ideal reactions. Furthermore, placing the non-metal source in a container with the opening facing upstream further constrains the non-metal source vapor to diffuse only directionally towards the metal source and substrate, preventing random diffusion. This approach avoids precursor waste, uneven substrate surface concentration, and insufficient non-metal diffusion to the precursor surface. It ensures a consistent metal / non-metal source component ratio at different locations on the substrate, resulting in the fabrication of large-area uniform thin films. The design incorporates a carrier gas flow rate control logic where the flow rate during the heating stage is greater than or equal to the flow rate during the cooling stage, which is greater than that during the isothermal growth stage. High flow rates during the heating stage prevent pre-reactions, low flow rates during the isothermal stage achieve precise precursor matching, and medium flow rates during the cooling stage prevent defects and secondary nucleation. This dynamic matching of non-metal and metal sources is achieved throughout the process, significantly reducing vacancy defects in the product and improving electrical and optoelectronic properties.

[0030] (2) This invention enables precise definition of the precursor supply timing through simple "flow rate control," which helps solve the problem of uneven film thickness and domain size caused by gas flow gradients in traditional chemical vapor deposition. The countercurrent diffusion mechanism makes the gas phase concentration distribution on the substrate surface more stable, and the resulting material has better optical and electrical quality. The preparation method provided by this invention only requires simple adjustments to the consumable layout of conventional single-temperature or multi-temperature tube furnaces to achieve the preparation of large-area, high-quality two-dimensional transition metal chalcogenides, which has broad prospects for industrial application. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the growth process of the two-dimensional transition metal sulfide of the present invention.

[0032] Figure 2 This is a microscopic observation result of the two-dimensional transition metal chalcogenide in Example 1.

[0033] Figure 3 This is a Raman diagram of the two-dimensional transition metal chalcogenide of Example 1.

[0034] Figure 4 Photoluminescence patterns of two-dimensional transition metal chalcogenides at different locations on the substrate of Example 1.

[0035] Figure 5 This is a microscopic observation result of the two-dimensional transition metal chalcogenide in Example 2.

[0036] Figure 6 This is a microscopic observation of the two-dimensional transition metal chalcogenide of Example 3.

[0037] Figure 7 This is a microscopic observation of the two-dimensional transition metal chalcogenide compound in Comparative Example 1.

[0038] Figure 8 This is a schematic diagram of the growth process of the two-dimensional transition metal chalcogenide in Comparative Example 2.

[0039] Figure 9 The image shows the microscopic observation results of the two-dimensional transition metal chalcogenide in Comparative Example 2. Detailed Implementation

[0040] The following will clearly and completely describe the concept of the present invention and its resulting technical effects with reference to embodiments. The described embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the invention.

[0041] In the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Unless otherwise specified, "room temperature" in this invention means 25°C ± 5°C, and "about" in this invention means an allowable error within ± 2%.

[0042] Example 1 In this embodiment, MoS2 was prepared using a countercurrent nonmetallic source supply method, and the layout of the growth apparatus is as follows: Figure 1 As shown, the specific preparation process is as follows: (1) Place 20mg of sulfur powder (non-metallic source) at the bottom of a single-port quartz tube and place the single-port quartz tube in the downstream heating zone of a chemical vapor deposition tube furnace, with the opening of the single-port quartz tube facing upstream, i.e. towards the direction of the carrier gas flow.

[0043] (2) 0.5 mg of sodium molybdate (metal source) was uniformly spread on the surface of a 9 mm × 9 mm × 2 mm soda-lime glass substrate. After complete drying in a forced-air drying oven, an ultra-thin soda-lime glass substrate of the same size but only 0.15 mm thick was placed on top. The assembly was placed in a muffle furnace and heat-treated to 700 °C at 20 °C / min for 30 min. After heat treatment, the two glass layers fused and bonded together to form a composite substrate containing the molybdenum source. The substrate was then placed in the heating zone at the center of a tube furnace, with the specific placement and carrier gas flow direction as shown in the figure. Figure 1 As shown.

[0044] (3) High-purity argon gas (99.999% purity) was continuously introduced at a flow rate of 50 sccm as the carrier gas. The argon gas flow direction was from the substrate to the single-port quartz tube, and the pressure inside the tube was 760 Torr. This was continued for 20 min to remove air. During the heating stage, the carrier gas flow rate was maintained at 50 sccm. The temperature was increased at a rate of 40 ℃ / min, raising the sulfur source to 150 ℃ and the substrate area to 750 ℃. At this time, the high-flow-rate carrier gas effectively blocked the backflow diffusion of sulfur vapor, preventing the substrate from being exposed prematurely. During the isothermal growth stage, the carrier gas flow rate was rapidly reduced to 5 sccm. The reduction in carrier gas resistance allowed the sulfur vapor to diffuse backflow to the substrate surface and react with the molybdenum source based on the concentration gradient. Heating was stopped after 30 min of temperature maintenance. During the cooling stage, the carrier gas flow rate was adjusted back to 50 sccm, and the system was allowed to cool naturally to room temperature.

[0045] Figure 2 The image shows the microscopic observation results of MoS2 in this embodiment. It can be seen that the synthesized nanosheets have a triangular morphology with neat edges and an average lateral size of about 17 μm.

[0046] Figure 3This is the Raman spectrum of MoS2 in this embodiment. The spectral peak corresponds to the Raman characteristic peak of MoS2, indicating that the obtained material is pure MoS2 material.

[0047] Figure 4 The image shows the photoluminescence of MoS2 at different locations on the substrate in this embodiment. The peaks correspond to the photoluminescence peaks of the monolayer MoS2 nanosheets, and the half-widths of the photoluminescence peaks at different locations are close, indicating that the quality of MoS2 is uniform at different locations on the substrate.

[0048] Example 2 To verify the ability of the present invention to regulate the growth process, the carrier gas flow rate in the isothermal growth stage of step (3) was changed, while the other conditions remained the same as in Example 1.

[0049] The carrier gas flow rate during the heat preservation stage is 7 sccm. Figure 5 The image shows the microscopic observation results of MoS2 in this embodiment. It can be seen that the synthesized nanosheets have a triangular morphology with neat edges and an average lateral size of about 10 μm.

[0050] Example 3 To verify the ability of the present invention to regulate the growth process, the carrier gas flow rate in the isothermal growth stage of step (3) was changed, while the other conditions remained the same as in Example 1.

[0051] The carrier gas flow rate during the heat preservation stage is 10 sccm. Figure 6 The image shows the microscopic observation results of MoS2 in this embodiment. It can be seen that the synthesized nanosheets have a triangular morphology with neat edges and an average lateral size of about 5 μm.

[0052] Comparative Example 1 The difference between this comparative example and Example 1 is that the flow rate during the isothermal stage is set to 15 sccm.

[0053] Figure 7 This indicates that there is almost no obvious nanosheet nucleation on the substrate surface, or only a very small number of particles of extremely small size. This proves that when the carrier gas dynamic pressure exceeds the diffusion driving force, the sulfur source cannot flow backward to the reaction zone, confirming the effectiveness of the "flow barrier mechanism" of this invention.

[0054] Comparative Example 2 This comparative example uses a traditional chemical vapor deposition layout, such as... Figure 8 As shown, 20 mg of sulfur powder was placed upstream, and a fixed carrier gas flow rate of 50 sccm was maintained throughout the process to directly blow sulfur vapor onto the substrate.

[0055] Figure 9 This is a microscopic observation result of MoS2 in this embodiment.

[0056] The results of the above comparative examples show that the countercurrent supply method proposed in this invention significantly improves the morphological controllability, crystal quality, and uniformity of optical quality of two-dimensional materials by avoiding premature exposure during the heating stage. Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the carrier gas flow rate during the cooling stage is the same as that during the isothermal stage.

[0057] Experiments revealed that the carrier gas during the cooling stage significantly impacts the surface morphology and properties of the final prepared molybdenum sulfide. If the carrier gas flow rate during the cooling stage is the same as or lower than that during the isothermal stage, a large number of particles will adhere to the surface of the nanosheets, severely affecting their performance. Conversely, if the carrier gas flow rate during the cooling stage is higher than, or even higher than, that during the heating stage, the prepared nanosheets will contain more sulfur vacancies, which will also greatly affect their performance.

[0058] Comparative Example 4 The difference between Comparative Example 4 and Comparative Example 2 is that 20 mg of sulfur powder was placed downstream and a pipe facing upstream was not used; otherwise, they were the same as Comparative Example 2.

[0059] Experiments have shown that if an upstream pipe is not used and sulfur powder is placed downstream, a large amount of sulfur is blown away when carrier gas is introduced, making it difficult for enough sulfur to diffuse to the surface of the precursor source, resulting in a significant decrease in the morphology and properties of the prepared molybdenum sulfide.

[0060] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for growing two-dimensional materials based on countercurrent non-metallic source supply, characterized in that, Includes the following steps: (1) Place the transition metal source and substrate in the central heating zone of the tube furnace, and place the solid non-metal source in a single-port container with the opening facing upstream, and place it in the non-metal source heating zone downstream of the airflow direction of the tube furnace. (2) Continuously introduce protective carrier gas into the tubular furnace, start the tubular furnace heating program, divide the growth process into a heating stage, an isothermal growth stage and a cooling stage, regulate the gas phase concentration of the non-metallic source by adjusting the flow rate of the carrier gas, and the flow rate of the carrier gas in each stage satisfies: the flow rate in the heating stage ≥ the flow rate in the cooling stage > the flow rate in the isothermal growth stage. After the cooling stage ends, keep the carrier gas continuously introduced to cool the tubular furnace to room temperature and obtain a two-dimensional transition metal chalcogenide.

2. The two-dimensional material growth method according to claim 1, characterized in that, The transition metal source mentioned in step (1) is a molybdenum source or a tungsten source. The molybdenum source includes at least one of molybdenum oxide, elemental molybdenum, molybdenum halide, and molybdate. The tungsten source includes at least one of tungsten oxide, elemental tungsten, tungsten halide, and tungstate. The substrate includes at least one of silicon / silicon dioxide, sapphire, fused glass, and mica. The solid non-metal source includes any one of sulfur powder, selenium powder, and tellurium powder.

3. The two-dimensional material growth method according to claim 1, characterized in that, In step (1), the transition metal source is placed between two substrates.

4. The two-dimensional material growth method according to claim 1, characterized in that, In step (1), the transition metal source is placed inside the bonded glass substrate and obtained by the following method: the transition metal source is uniformly spread on the surface of the first glass substrate, dried and covered with the second glass substrate, and placed in a muffle furnace for heat treatment to obtain bonded glass containing the transition metal source; the heat treatment is performed at 680~720℃ for 30~60min, and the heating rate during the heat treatment is 10~30 ℃ / min.

5. The two-dimensional material growth method according to claim 1, characterized in that, In step (2), the protective carrier gas includes at least one of nitrogen, argon, nitrogen / hydrogen mixture, and argon / hydrogen mixture. After the tubular furnace heating program is started, the heating temperature of the non-metallic source heating zone is 100~500℃, and the heating rate of the sulfur source is 15~55℃ / min.

6. The two-dimensional material growth method according to claim 1, characterized in that, In step (2), the heating rate of the central heating zone during the heating stage is 15~50 ℃ / min, the cooling stage is natural cooling, and the final temperature of the cooling stage is 20-60℃.

7. The two-dimensional material growth method according to claim 1, characterized in that, In step (2), the rate of introduction of protective carrier gas during the heating stage is 30-100 sccm; the rate of introduction of protective gas during the isothermal stage is 3-10 sccm; the rate of introduction of protective gas during the cooling stage is 10-100 sccm; the holding time during the holding stage is 2-60 min; and the pressure in the tubular furnace is 760 torr.

8. The two-dimensional material growth method according to claim 1, characterized in that, The molar ratio of transition metal source to sulfur source is 1:3 to 1:

100.

9. A two-dimensional transition metal chalcogenide prepared by the growth method according to any one of claims 1 to 8.

10. The application of the two-dimensional transition metal chalcogenide of claim 9 in the fields of integrated circuits, flexible electronic devices and photoelectric detection.

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