Molybdenum tungsten disulfide nanosheet and preparation method thereof

Abstract

This invention provides molybdenum disulfide tungsten nanosheets and their preparation method, belonging to the field of nanomaterials. The method includes: spin-coating a molybdenum source solution onto a first substrate, and spin-coating a mixed solution of a tungsten source and a catalyst onto a second substrate; placing a sulfur source in a first temperature zone of a partitioned heating device, placing the first and second substrates in a second temperature zone of the same device, and controlling the spacing between the first and second substrates; placing the partitioned heating device in a carrier gas atmosphere, with the first temperature zone located upstream of the second temperature zone relative to the carrier gas flow direction; and heating the partitioned heating device using a set heating mode to obtain molybdenum disulfide tungsten nanosheets. By adjusting the spacing between the first and second substrates, the composition of the grown monolayer two-dimensional molybdenum disulfide tungsten alloy can be controlled, with the tungsten composition adjustable over a wide range from 0 to 0.8.

Description

Technical Field

[0001] This application relates to the field of nanomaterials technology, and in particular to a molybdenum disulfide tungsten nanosheet and its preparation method. Background Technology

[0002] Transition metal dichalcogenides, such as MoS2, MoSe2, WS2, and WSe2, have attracted considerable interest due to their atomically thin structure, unique electronic and optical properties, and potential applications in nanoscale semiconductor devices. Unlike graphene, which has a zero bandgap, these two-dimensional materials possess a direct bandgap and can emit light at room temperature, which is crucial for their applications in electronics and optoelectronics. A sufficiently large and tunable bandgap is essential for the full application of two-dimensional materials in optoelectronics; therefore, bandgap engineering is of great significance for the commercial development of two-dimensional materials. Material alloying is a highly effective way to achieve tunable bandgap. Considering that the direct bandgap of monolayer MoS2 and WS2 are approximately 1.8 eV and 2.0 eV, respectively, and that these two materials share similar atomic structures, they are well-suited for creating alloy systems with tunable bandgaps through alloy construction.

[0003] Currently, the preparation of two-dimensional molybdenum disulfide tungsten alloys is mainly achieved through two technical routes: top-down and bottom-up. Compared to the cumbersome top-down methods such as mechanical exfoliation, the bottom-up method, represented by chemical vapor deposition (CVD), has many advantages such as higher yield, larger size, and better controllability, and is widely used in the preparation of two-dimensional materials. However, due to the different evaporation temperatures of commonly used tungsten and molybdenum sources, and the different growth temperatures of MoS2 and WS2, the preparation of MoS2 using CVD faces challenges. (1-x) W x Achieving controllable composition of S2 alloys remains a considerable challenge. Summary of the Invention

[0004] This application provides a two-dimensional molybdenum disulfide tungsten nanosheet and its preparation method, in order to solve the technical problem of uncontrollable chemical composition of molybdenum disulfide tungsten nanosheet.

[0005] In a first aspect, this application provides a method for preparing molybdenum disulfide tungsten nanosheets, the method comprising:

[0006] A molybdenum source solution was spin-coated onto a first substrate, and a mixed solution of a tungsten source and a catalyst was spin-coated onto a second substrate.

[0007] The sulfur source is placed in the first temperature zone of the partitioned heating device, the first substrate and the second substrate are placed in the second temperature zone of the partitioned heating device, and the spacing between the first substrate and the second substrate is controlled.

[0008] The partitioned heating device is placed in a carrier gas atmosphere, with the first temperature zone located upstream of the second temperature zone relative to the carrier gas flow direction.

[0009] The partitioned heating device heats the material using a set heating method to obtain molybdenum disulfide tungsten nanosheets.

[0010] Optionally, the distance between the first substrate and the second substrate is 0cm to 5cm.

[0011] Optionally, the molybdenum source solution is an aqueous solution of soluble molybdate, the tungsten source is an aqueous solution of soluble tungstate, the sulfur source is elemental sulfur, and the catalyst is an alkaline solution containing alkali metal ions.

[0012] Optionally, the molybdenum source solution includes at least one of sodium molybdate solution, ammonium molybdate solution, and potassium molybdate solution; the tungsten source includes at least one of sodium tungstate solution, potassium tungstate solution, and ammonium tungstate solution; and the catalyst includes at least one of sodium hydroxide solution and potassium hydroxide solution.

[0013] Optionally, a transition temperature zone is set between the first temperature zone and the second temperature zone, and the distance between the first temperature zone and the second temperature zone is 45cm to 55cm.

[0014] Optionally, the heating temperature of the first temperature zone is 150℃~250℃; and / or,

[0015] The heating temperature of the transition temperature zone is 300℃~400℃; and / or

[0016] The heating temperature of the second temperature zone is 750℃~900℃, and the holding time of the second temperature zone is 5min~20min.

[0017] Optionally, the spin coating is a multi-step spin coating, the spin coating speed is 1000rpm~4000rpm, and the spin coating time is ≥30s.

[0018] Optionally, the first substrate includes at least one of a quartz wafer, a silicon wafer, and sapphire, and the second substrate includes at least one of a silicon wafer and sapphire.

[0019] Secondly, this application provides a molybdenum disulfide tungsten nanosheet, which is prepared by the method described in any embodiment of the first aspect, and the chemical formula of the molybdenum disulfide tungsten nanosheet is: Mo(1-x)WxS2, wherein 0≤x≤0.8.

[0020] Optionally, if the second substrate is a silicon wafer, the average size of the molybdenum disulfide tungsten nanosheets is 50 μm to 70 μm;

[0021] If the second substrate is sapphire, the average size of the molybdenum disulfide tungsten nanosheets is 15 μm to 25 μm.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a two-dimensional molybdenum disulfide tungsten nanosheet and its preparation method. By adjusting the spacing between the first substrate and the second substrate, the composition of the grown monolayer two-dimensional molybdenum disulfide tungsten alloy can be controlled, and the tungsten composition has a large adjustable range from 0 to 0.8.

[0024] Furthermore, by using transition metal salt solutions as both molybdenum and tungsten sources, the melting point of the reactants was effectively lowered, overcoming the problem of inconsistent evaporation temperatures associated with commonly used oxide tungsten and molybdenum sources. The spin-coating method on the substrate, compared to using reactant powders, is more conducive to obtaining materials with better uniformity and higher coverage on the substrate. Simultaneously, the catalyst better maintains the fluidity of intermediate products formed during the growth of molybdenum disulfide tungsten. Thus, the preparation of single-layer two-dimensional molybdenum disulfide tungsten alloy nanosheets with good crystal quality was successfully achieved.

[0025] In particular, this application enables direct chemical vapor deposition of a single layer of two-dimensional molybdenum disulfide tungsten alloy on commonly used substrates, including sapphire and silicon, effectively avoiding contamination and defects introduced through cumbersome mechanical stripping processes. Furthermore, the fabrication process is simple, has low production costs, and offers good controllability, making it suitable for mass production. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic flowchart illustrating a method for preparing molybdenum disulfide tungsten nanosheets provided in this application embodiment;

[0029] Figure 2 A schematic diagram of the experimental method for preparing two-dimensional molybdenum disulfide tungsten nanosheets provided in the embodiments of this application;

[0030] Figure 3 An optical micrograph of a single-layer two-dimensional molybdenum disulfide tungsten nanosheet provided in Example 1 of this application;

[0031] Figure 4 An optical micrograph of a single-layer two-dimensional molybdenum disulfide tungsten nanosheet provided in Example 2 of this application;

[0032] Figure 5 Raman spectra of monolayer two-dimensional molybdenum disulfide tungsten nanosheets with spacings of 3 cm, 4 cm and 5 cm between the first and second substrates provided in the embodiments of this application;

[0033] Figure 6 The photoluminescence spectra of monolayer two-dimensional molybdenum disulfide tungsten nanosheets with a spacing of 3 cm, 4 cm and 5 cm between the first substrate and the second substrate provided in the embodiments of this application are shown.

[0034] Figure 7 Raman spectrum (7a) and photoluminescence spectrum (7b) of the monolayer two-dimensional molybdenum disulfide tungsten nanosheet provided in Example 5 of this application;

[0035] Figure 8 An optical micrograph of two-dimensional molybdenum disulfide tungsten nanosheets provided in Comparative Example 1 of this application;

[0036] Figure 9 An optical microscopic image of two-dimensional molybdenum disulfide tungsten nanosheets provided in Comparative Example 2 of this application;

[0037] Figure 10 An optical micrograph of two-dimensional molybdenum disulfide tungsten nanosheets provided in Comparative Example 3 of this application;

[0038] Figure 11 An optical micrograph of two-dimensional molybdenum disulfide tungsten nanosheets provided in Comparative Example 4 of this application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0041] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0043] Firstly, this application provides a method for preparing molybdenum disulfide tungsten nanosheets, please refer to [link to method]. Figure 1 The method includes:

[0044] S1. Spin-coat the molybdenum source solution onto the first substrate, and spin-coat the mixed solution of the tungsten source and the catalyst onto the second substrate;

[0045] In some embodiments, before step S1, a first substrate of 1cm×1cm and a second substrate of 1.5cm×1.5cm are cut, and the first substrate and the second substrate are ultrasonically cleaned in acetone, isopropanol and deionized water for 15 minutes in sequence, dried with nitrogen, and then treated with an oxygen plasma treatment machine for 5 minutes.

[0046] In some embodiments, prior to step S1, the preparation of a molybdenum source solution, a tungsten source solution, and a catalyst solution is further included, wherein the molar concentrations of the molybdenum source solution, the tungsten source solution, and the catalyst solution are all 0.005 mol / L to 0.010 mol / L.

[0047] The molar concentrations of the molybdenum source solution, tungsten source solution, and catalyst solution can all be 0.005 mol / L, 0.006 mol / L, 0.007 mol / L, 0.008 mol / L, 0.009 mol / L, 0.010 mol / L, etc.

[0048] In some embodiments, the molybdenum source solution is an aqueous solution of soluble molybdate, the tungsten source is an aqueous solution of soluble tungstate, the sulfur source is elemental sulfur, and the catalyst is an alkaline solution containing alkali metal ions.

[0049] In some embodiments, the molybdenum source solution includes at least one of sodium molybdate solution, ammonium molybdate solution, and potassium molybdate solution; the tungsten source includes at least one of sodium tungstate solution, potassium tungstate solution, and ammonium tungstate solution; and the catalyst includes at least one of sodium hydroxide solution and potassium hydroxide solution.

[0050] By employing transition metal salt solutions as both molybdenum and tungsten sources, the melting point of the reactants was effectively lowered, overcoming the problem of inconsistent evaporation temperatures associated with commonly used oxide tungsten and molybdenum sources. The spin-coating method on the substrate, compared to using reactant powders, is more conducive to obtaining materials with better uniformity and higher coverage on the substrate. Simultaneously, the catalyst better maintains the fluidity of intermediate products formed during the growth of molybdenum disulfide tungsten. Thus, the preparation of single-layer two-dimensional molybdenum disulfide tungsten alloy nanosheets with good crystal quality was successfully achieved.

[0051] In some embodiments, the spin coating is a multi-step spin coating, the spin coating speed is 1000 rpm to 4000 rpm, and the spin coating time is ≥30 s.

[0052] The spin coating speed can be 1000rpm, 1500rpm, 2000rpm, 3000rpm, 3500rpm, 4000rpm, etc., and the spin coating time can be 30s, 35s, 40s, 45s, 50s, etc.

[0053] Furthermore, when the spin coating is a two-step spin coating, the rotation speed of the first spin coating is 1000rpm~2000rpm and the time of the first spin coating is ≤30s; the rotation speed of the second spin coating is 2000rpm~4000rpm and the time of the first spin coating is ≥30s.

[0054] The spin coating speed for the first step can be 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm, 2000 rpm, etc., and the spin coating time for the first step can be 10 s, 15 s, 20 s, 25 s, 30 s, etc. The spin coating speed for the second step can be 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, etc., and the spin coating time for the second step can be 30 s, 35 s, 40 s, 45 s, 50 s, etc.

[0055] In some embodiments, the first substrate includes at least one of a quartz wafer, a silicon wafer, and sapphire, and the second substrate includes at least one of a silicon wafer and sapphire.

[0056] S2. Place the sulfur source into the first temperature zone of the partitioned heating device, place the first substrate and the second substrate into the second temperature zone of the partitioned heating device, and control the spacing between the first substrate and the second substrate.

[0057] In some embodiments, the distance between the first substrate and the second substrate is 0 cm to 5 cm.

[0058] The positive effects of controlling the spacing between the first and second substrates to be 0cm to 5cm include: controllable composition of the grown monolayer two-dimensional molybdenum disulfide tungsten alloy by adjusting the spacing, with the tungsten composition adjustable over a wide range from 0 to 0.8. A negative effect of excessively large spacing is that it extends beyond the central heating zone, leading to unstable temperature control. Suitable spacing values ​​include 0cm, 0.5cm, 1cm, 2cm, 2.5cm, 3cm, 4cm, 4.5cm, and 5cm.

[0059] S3. Place the partitioned heating device in a carrier gas atmosphere, with the first temperature zone located upstream of the second temperature zone relative to the carrier gas flow direction.

[0060] Elemental sulfur is located in the first temperature zone, and the first and second substrates are located in the second temperature zone. After heating, the elemental sulfur sublimates and flows with the carrier gas to the second temperature zone to react. Therefore, relative to the direction of carrier gas flow, the first temperature zone needs to be located upstream of the second temperature zone.

[0061] In some embodiments, a transition temperature zone is set between the first temperature zone and the second temperature zone, and the distance between the first temperature zone and the second temperature zone is 45cm to 55cm.

[0062] A transition temperature zone is set for transitioning temperatures, avoiding interference between the first and second temperature zones.

[0063] The positive effects of controlling the distance between the first and second temperature zones to be 45cm to 55cm: Too small or too large a distance will cause the raw material to deviate from the center of the temperature zone, easily leading to poor temperature control. This distance can be 45cm, 47cm, 49cm, 51cm, 53cm, 55cm, etc.

[0064] In some embodiments, the first substrate is located upstream of the second substrate relative to the direction of carrier gas flow.

[0065] In some embodiments, the carrier gas is an inert gas, and the flow rate of the carrier gas is ≥100 sccm.

[0066] By using an inert gas to eliminate interference from air, the flow rate of the carrier gas can be 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, etc.

[0067] In some implementations, the zone heating device can be a three-zone tubular furnace.

[0068] S4. The partitioned heating device is heated in a set heating mode to obtain molybdenum disulfide tungsten nanosheets.

[0069] In some embodiments, the heating temperature of the first temperature zone is 150°C to 250°C; and / or,

[0070] The heating temperature of the transition temperature zone is 300℃~400℃; and / or

[0071] The heating temperature of the second temperature zone is 750℃~900℃, and the holding time of the second temperature zone is 5min~20min.

[0072] The positive effects of controlling the heating temperature of the first temperature zone to be between 150℃ and 250℃ are as follows: Too low a temperature is detrimental to the evaporation of the sulfur source, while too low a temperature can lead to excessive sulfur vapor evaporation, which is unfavorable for the reaction. This heating temperature can be 150℃, 170℃, 190℃, 210℃, 230℃, 250℃, etc.

[0073] The positive effects of controlling the heating temperature of the transition zone to 300℃~400℃: This temperature lies between two heating zones, and setting a reasonable temperature avoids cross-temperature interference between the heating zones. Heating temperatures that are too high or too low are detrimental to maintaining temperature stability in the heating zone. The heating temperature of this transition zone can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc.

[0074] The positive effects of controlling the heating temperature of the second temperature zone to be between 750℃ and 900℃ are as follows: if the heating temperature is too low, the required reaction temperature will not be reached; if the temperature is too high, the evaporation rate of the reactants on the substrate will be too fast, resulting in incomplete reaction with sulfur vapor and smaller material size. The heating temperature of this second temperature zone can be 750℃, 770℃, 800℃, 830℃, 860℃, 880℃, 900℃, etc.

[0075] The positive effects of controlling the holding time in the second temperature zone to be 5 to 20 minutes are as follows: Too short a holding time leads to incomplete reaction and smaller material size; too long a time can easily result in thick layers, reducing the proportion of single layers obtained. The holding time can be 5 minutes, 7 minutes, 10 minutes, 20 minutes, etc.

[0076] In some embodiments, the heating rates of the first temperature zone, the second temperature zone, and the transition temperature zone are the same, and are all 10°C / min to 40°C / min.

[0077] The heating rate can be 10℃ / min, 15℃ / min, 20℃ / min, 25℃ / min, 35℃ / min, 40℃ / min, etc.

[0078] The method provided in this application can directly achieve the direct chemical vapor deposition of a single layer of two-dimensional molybdenum disulfide tungsten alloy on commonly used substrates, including sapphire and silicon, effectively avoiding contamination and defects introduced by the cumbersome mechanical stripping process. Furthermore, the fabrication process is simple, has low production costs, and offers good controllability, making it suitable for mass production.

[0079] Secondly, this application provides a molybdenum disulfide tungsten nanosheet, which is prepared by the method described in any embodiment of the first aspect, and the chemical formula of the molybdenum disulfide tungsten nanosheet is: Mo(1-x)WxS2, wherein 0≤x≤0.8.

[0080] Depending on the desired composition of the two-dimensional molybdenum disulfide tungsten nanosheets, the spacing between the first and second substrates can be adjusted. A smaller spacing results in a lower tungsten content in the molybdenum disulfide tungsten nanosheets; a larger spacing results in a higher tungsten content. In the chemical formula of the molybdenum disulfide tungsten nanosheets, x can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc.

[0081] In some embodiments, if the second substrate is a silicon wafer, the average size of the molybdenum disulfide tungsten nanosheets is 50 μm to 70 μm;

[0082] If the second substrate is sapphire, the average size of the molybdenum disulfide tungsten nanosheets is 15 μm to 25 μm.

[0083] If the second substrate is a silicon wafer, the average size of the molybdenum disulfide tungsten nanosheets can be 50μm, 55μm, 60μm, 65μm, 70μm, etc.; if the second substrate is sapphire, the average size of the molybdenum disulfide tungsten nanosheets can be 15μm, 17μm, 19μm, 21μm, 23μm, 25μm, etc.

[0084] The monolayer two-dimensional molybdenum disulfide tungsten nanosheets obtained by the method of this application have excellent crystal quality, large size, and high uniformity, and have great potential for practical applications.

[0085] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0086] Example 1

[0087] The method for preparing the monolayer two-dimensional molybdenum disulfide tungsten nanosheets in this embodiment includes the following steps:

[0088] S21. Dissolve 155 mg of sodium molybdate in 100 ml of deionized water to obtain a molybdenum source solution; dissolve 220 mg of sodium tungstate and 30 mg of sodium hydroxide in 100 ml of deionized water to obtain a mixed solution of tungsten source and catalyst.

[0089] S22. Cut a 1cm×1cm quartz wafer (first substrate) and a 1.5cm×1.5cm silicon wafer (second substrate) as target substrates. Clean them sequentially with acetone, isopropanol and deionized water by ultrasonication for 15min, and dry them with nitrogen. Then treat them with oxygen plasma for 5min. Add the prepared molybdenum source and tungsten source solutions to them respectively, spin coat them at 1500rpm for 20s, spin coat them at 3000rpm for 40s, and then air dry them.

[0090] S23. Place the spin-coated first and second substrates face up in a quartz boat and lay them flat. The first substrate is located upstream of the second substrate, and the distance between the first and second substrates is set to 3cm. Place the quartz boat into the second temperature zone of a 3-inch three-zone tube furnace. At the same time, place a ceramic boat containing 400mg of sulfur powder in the first temperature zone upstream, with a distance of 50cm between the quartz boat and the ceramic boat.

[0091] S24. Perform CVD growth. Turn on the chemical vapor deposition system, evacuate and purge the gas, and control the carrier gas (nitrogen) flow rate at 250 sccm, maintaining the gas pressure at atmospheric pressure. In the first temperature zone, transition temperature zone, and second temperature zone, the temperature is increased from room temperature at a rate of 30℃ / min, reaching 200℃, 350℃, and 850℃ respectively, and maintained for 10 minutes (growth time).

[0092] S25. After the reaction is complete and the system is naturally cooled to room temperature, the sample is taken out, thus obtaining two-dimensional molybdenum disulfide tungsten nanosheets with specific components.

[0093] Combination Figure 5 and Figure 6 Raman and photoluminescence spectroscopy revealed that the tungsten content in the grown monolayer two-dimensional molybdenum disulfide tungsten nanosheets was 0.5%, with the chemical formula Mo. 0.5 W 0.5 S2. Figure 2 The results show that the monolayer two-dimensional molybdenum disulfide tungsten single crystals grown on the silicon substrate have excellent uniformity, with the largest single crystal molybdenum disulfide tungsten triangular domain having a side length exceeding 70 μm.

[0094] Example 2

[0095] The difference between this embodiment and Embodiment 1 is that:

[0096] The second substrate is sapphire, and the distance between the first and second substrates is set to 3 cm. The remaining parameters of the preparation method are the same as in Example 1.

[0097] Combination Figure 5 and Figure 6 Raman and photoluminescence spectroscopy revealed that the tungsten content in the grown monolayer two-dimensional molybdenum disulfide tungsten nanosheets was 0.5%, with the chemical formula Mo. 0.5W 0.5 S2. Figure 3 The monolayer two-dimensional molybdenum disulfide tungsten nanosheets grown on sapphire exhibit high uniformity, with an average size of approximately 20 μm.

[0098] Example 3

[0099] The difference between this embodiment and Embodiment 1 is that:

[0100] The second substrate is sapphire, and the distance between the first and second substrates is set to 4 cm. The remaining parameters of the preparation method are the same as in Example 1.

[0101] Combination Figure 5 and Figure 6 Raman and photoluminescence spectroscopy revealed that the tungsten content in the grown monolayer two-dimensional molybdenum disulfide tungsten nanosheets was 0.65%, with the chemical formula Mo. 0.35 W 0.65 S2.

[0102] Example 4

[0103] The difference between this embodiment and Embodiment 1 is that:

[0104] The second substrate is sapphire, and the distance between the first and second substrates is set to 5 cm. The remaining parameters of the preparation method are the same as in Example 1.

[0105] Combination Figure 5 and Figure 6 Raman and photoluminescence spectroscopy revealed that the tungsten content in the grown monolayer two-dimensional molybdenum disulfide tungsten nanosheets was 0.8%, with the chemical formula Mo. 0.2 W 0.8 S2.

[0106] Example 5

[0107] The difference between this embodiment and Embodiment 1 is that:

[0108] The second substrate is sapphire, and the distance between the first and second substrates is set to 0 cm. The remaining parameters of the preparation method are the same as in Example 1.

[0109] Combination Figure 7 Raman and photoluminescence spectra showed that the tungsten content in the monolayer two-dimensional molybdenum disulfide tungsten nanosheets obtained by growth was 0, and the chemical formula was written as MoS2.

[0110] Comparative Example 1

[0111] The difference between this embodiment and Embodiment 1 is that:

[0112] The second substrate is sapphire, the distance between the first and second substrates is set to 5 cm, and the heat treatment (growth) time is 3 min. The remaining parameters of the preparation method are the same as in Example 1.

[0113] Combination Figure 4 and Figure 8 Optical microscopic images show that shorter growth times result in smaller material sizes.

[0114] Comparative Example 2

[0115] The second substrate is sapphire, the distance between the first and second substrates is set to 5 cm, and the heat treatment (growth) time is 30 min. The remaining parameters of the preparation method are the same as in Example 1.

[0116] Combination Figure 4 and Figure 9 Optical microscopic images show that excessively long growth times can easily lead to overreaction and the formation of thicker materials, which is detrimental to product acquisition. Only when the reaction time is appropriate (5–20 min) can the obtained material be larger in size with less thick layer formation.

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 1 is that:

[0119] The second substrate is sapphire, the distance between the first and second substrates is 5 cm, and the heating temperature of the second temperature zone is 700℃. The remaining parameters of the preparation method are the same as in Example 1.

[0120] Combination Figure 4 and Figure 10 Optical microscopic images show that when the growth temperature is too low, the required temperature for the reaction is not reached, and the material cannot be grown.

[0121] Comparative Example 4

[0122] The difference between this embodiment and Embodiment 1 is that:

[0123] The second substrate is sapphire, the distance between the first and second substrates is 5 cm, and the heating temperature of the second temperature zone is 950℃. The remaining parameters of the preparation method are the same as in Example 1.

[0124] Combination Figure 4 and Figure 11 Optical microscopic images show that at higher growth temperatures, excessive evaporation of the reactants results in very small material sizes, which is detrimental to product acquisition. Only when the reaction temperature is appropriate (750℃~900℃) can larger material sizes be obtained.

[0125] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing molybdenum disulfide tungsten nanosheets, characterized in that, The method includes: A molybdenum source solution was spin-coated onto a first substrate, and a mixed solution of a tungsten source and a catalyst was spin-coated onto a second substrate. The sulfur source is placed in the first temperature zone of the partitioned heating device, and the first substrate and the second substrate are placed separately in the second temperature zone of the partitioned heating device, while controlling the spacing between the first substrate and the second substrate. The partitioned heating device is placed in a carrier gas atmosphere, with the first temperature zone located upstream of the second temperature zone relative to the carrier gas flow direction. The partitioned heating device heats the material using a set heating mode to obtain molybdenum disulfide tungsten nanosheets. The chemical formula of the molybdenum disulfide tungsten nanosheets is: Mo (1-x) W x S2, where 0.5 ≤ x ≤ 0.8; The distance between the first substrate and the second substrate is 3cm to 5cm; The first substrate includes at least one of a quartz wafer, a silicon wafer, and sapphire, and the second substrate includes at least one of a silicon wafer and sapphire. A transition temperature zone is set between the first temperature zone and the second temperature zone, and the distance between the first temperature zone and the second temperature zone is 45cm~55cm; The heating temperature of the first temperature zone is 150℃~250℃; the heating temperature of the transition temperature zone is 300℃~400℃; the heating temperature of the second temperature zone is 750℃~900℃, and the holding time of the second temperature zone is 5min~20min; The catalyst is an alkaline solution containing alkali metal ions.

2. The method according to claim 1, characterized in that, The molybdenum source solution is an aqueous solution of soluble molybdate, the tungsten source is an aqueous solution of soluble tungstate, and the sulfur source is elemental sulfur.

3. The method according to claim 2, characterized in that, The molybdenum source solution includes at least one of sodium molybdate solution, ammonium molybdate solution, and potassium molybdate solution; the tungsten source includes at least one of sodium tungstate solution, potassium tungstate solution, and ammonium tungstate solution; and the catalyst includes at least one of sodium hydroxide solution and potassium hydroxide solution.

4. The method according to claim 1, characterized in that, The spin coating is a multi-step spin coating, the spin coating speed is 1000rpm~4000rpm, and the spin coating time is ≥30s.

Images