Method for growing MoSe2 / WSe2 transverse heterojunction nanosheet by aluminum powder catalytic CVD (chemical vapor deposition)

Abstract

The invention discloses a method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalytic CVD (chemical vapor deposition), which comprises the following steps: S1, pretreating a SiO2 / Si sheet to serve as a growth substrate; s2, spin-coating a precursor solution containing a molybdenum source and a tungsten source to the surface of the growth substrate; s3, the growth substrate obtained in the S2, aluminum powder and selenium powder are jointly placed in a two-temperature-zone tube furnace, the growth substrate and the aluminum powder are jointly placed in a second temperature zone of the tube furnace, and the selenium powder is placed in a first temperature zone; the surface, coated with the precursor, of the growth substrate faces the aluminum powder; and S4, heating the first temperature zone to 400 DEG C in an inert atmosphere, and simultaneously heating the second temperature zone to 900-950 DEG C to grow the MoSe2 / WSe2 transverse heterojunction nanosheet. Compared with the prior art, the method for growing the MoSe2 / WSe2 transverse heterojunction nanosheet through aluminum powder catalytic CVD has the advantages that hydrogen is not used, growth is more controllable, and the experimental process is safer.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a method for growing MoSe2 / WSe2 transverse heterojunction nanosheets by aluminum powder catalytic CVD. Background Technology

[0002] With the development of modern society, the environmental problems caused by human energy consumption are becoming increasingly severe. Developing low-pollution, sustainable, and renewable clean energy has become a key concern for countries worldwide. Hydrogen energy, as a pollution-free, high-energy, and long-term storable secondary clean energy source, plays a crucial role in the renewable energy system. Therefore, finding efficient hydrogen production methods and low-cost hydrogen production materials has become a key task in the current renewable energy field. Hydrogen can be produced in various ways, such as traditional fossil fuel conversion, steam reforming, and partial oxidation technologies, as well as alternative renewable methods such as electrocatalytic water splitting, photocatalysis, and biohydrogen production. Among these, using renewable energy for electrocatalytic water splitting to produce hydrogen is considered one of the important clean energy technologies for achieving sustainable development and has received increasing attention in recent years.

[0003] Noble metals such as Pt and Pb possess excellent electrocatalytic hydrogen production performance, but their scarcity and high cost severely limit their application in basic research and practical applications. Two-dimensional nanomaterials, due to their high specific surface area and tunable electronic properties, have broad application prospects in the field of catalysis. Among them, MoSe2 exhibits a near-ideal hydrogen adsorption free energy, WSe2 possesses bipolar semiconductor properties, and the interfacial charge redistribution and pn heterojunction effect resulting from their formation as heterostructures combine to make MoSe2 / WSe2 heterojunctions promising materials for electrocatalytic hydrogen production. Methods for preparing MoSe2 / WSe2 heterojunctions mainly include mechanical exfoliation transfer, liquid-phase synthesis, and chemical vapor deposition (CVD). CVD is the most commonly used method, yielding materials with high crystal quality, clean interfaces, good structural integrity, and suitability for constructing electronic devices. In the process of growing MoSe2 / WSe2 lateral heterojunctions using CVD, hydrogen is often used as a carrier gas or reactant gas to catalyze the reduction and selenization of the precursor and promote the lateral growth of the two-dimensional material.

[0004] However, there are some significant problems with using hydrogen: First, hydrogen is highly reactive, which may lead to excessively high nucleation density in the grown two-dimensional materials. Additionally, hydrogen can erode the material edges, hindering the acquisition of high-quality heterojunctions. Second, precise control of hydrogen is difficult; even slight fluctuations in its flow rate and concentration can significantly affect the nucleation and growth kinetics, making it difficult to precisely control the number of layers, stacking order, and interface quality of the heterojunction. Furthermore, hydrogen is a flammable and explosive gas, posing potential risks to its safe use in laboratories and future large-scale production.

[0005] Therefore, in order to obtain MoSe2 / WSe2 lateral heterojunctions with higher controllability, better quality, and safer process, it is particularly important to develop a new CVD growth method that can reduce or even avoid the use of hydrogen. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned technical defects and provide a method for growing MoSe2 / WSe2 transverse heterojunction nanosheets by aluminum powder catalytic CVD, which avoids the use of hydrogen gas and has the characteristics of more controllable growth and safer experimental process.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD, comprising the following steps: S1: SiO2 / Si wafers after pretreatment, used as the growth substrate; S2: Spin-coat a precursor solution containing molybdenum and tungsten sources onto the surface of the growth substrate; S3: The growth substrate obtained in S2 is placed together with aluminum powder and selenium powder in a two-temperature zone tube furnace, wherein: The growth substrate and aluminum powder are placed together in the second temperature zone of the tube furnace, while the selenium powder is placed in the first temperature zone. The growth substrate is coated with a precursor facing the aluminum powder. S4: In an inert atmosphere, heat the first temperature zone to 400℃ while simultaneously heating the second temperature zone to 900-950℃ to grow MoSe2 / WSe2 lateral heterojunction nanosheets.

[0008] Preferably, the pretreatment in S1 includes sequential ultrasonic cleaning with acetone, ethanol and deionized water, followed by UV cleaning to enhance hydrophilicity.

[0009] Preferably, in the precursor solution of S2, the molybdenum source is anhydrous sodium molybdate, and the tungsten source is anhydrous sodium tungstate. After being dissolved in deionized water, the solutions are spin-coated at 3000 rpm / s for 30 seconds.

[0010] Preferably, the amount of aluminum powder used in S3 is 30 mg, and the inert atmosphere in S4 is argon gas with a gas flow rate of 80 sccm.

[0011] Preferably, in step S4, the first temperature zone is heated to 400°C for 20 minutes and held for 15 minutes. The second temperature zone is heated to 900-950℃ for 20 minutes and held for 15-20 minutes. After growth, the temperature is allowed to drop naturally to 500-600℃ before the tubular furnace cavity is opened to cool to room temperature.

[0012] Preferably, the SiO2 / Si sheet in S1 has a size of 1cm × 1cm; Acetone, ethanol and deionized water were each ultrasonically cleaned for 10 minutes, and then treated with UV cleaning machine for 5 minutes.

[0013] This invention discloses a method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalytic CVD. The nanosheets are formed by laterally connecting MoSe2 regions and WSe2 regions in the same plane, with a clear and continuous interface and no edge defects caused by hydrogen etching.

[0014] Compared with the prior art, the advantages of the present invention are: the MoSe2 / WSe2 lateral heterojunction prepared by the method provided by the present invention has the characteristics of higher growth controllability and film uniformity, and avoids the use of hydrogen gas in general CVD growth process, making the growth process safer. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of MoSe2 / WSe2 transverse heterojunction nanosheets grown by aluminum powder-catalyzed CVD, as provided in this embodiment of the invention. Figure 2 This is an optical microscope image of WSe2 after aluminum powder-catalyzed CVD growth, provided in an embodiment of the present invention. Figure 3 The image shown is an SEM image of WSe2 after aluminum powder catalyzed CVD growth in this embodiment of the invention. The magnification is 200x, and the growth state of the triangular WSe2 can be clearly seen. Figure 4 The Raman spectrum of WSe2 after aluminum powder-catalyzed CVD growth in the embodiment of the present invention shows the characteristic peaks of WSe2, indicating the growth of WSe2 on the SiO2 / Si substrate. Figure 5 An optical microscope image of MoSe2 grown by CVD with aluminum powder as a catalyst, provided in an embodiment of the present invention. Figure 6The image shown is an SEM image of MoSe2 grown by CVD with aluminum powder in an embodiment of the present invention. The image is magnified 1000 times and clearly shows the growth of triangular MoSe2. Figure 7 The Raman spectrum of MoSe2 after CVD growth of WSe2 using aluminum powder provided in this embodiment of the invention shows the characteristic peaks of MoSe2, indicating the growth of MoSe2 on the SiO2 / Si substrate. Figure 8 An optical microscope image of the MoSe2 / WSe2 lateral heterojunction after aluminum powder-catalyzed CVD growth provided in this embodiment of the invention. Figure 9 The image provided in this embodiment of the invention shows the SEM image of the MoSe2 / WSe2 lateral heterojunction after aluminum powder-catalyzed CVD growth. The magnification is 1200 times, and it can be clearly seen that the MoSe2 / WSe2 lateral heterojunction grows uniformly on the SiO2 / Si substrate. Figure 10 The image provided in this embodiment of the invention is a SEM image of the MoSe2 / WSe2 lateral heterojunction after aluminum powder-catalyzed CVD growth. The magnification is 30,000 times, and the growth status of the MoSe2 / WSe2 lateral heterojunction can be clearly seen. Figure 11 The Raman spectrum of the MoSe2 / WSe2 lateral heterojunction after aluminum powder catalyzed CVD growth in the embodiment of the present invention shows the characteristic peaks of MoSe2 and WSe2, indicating the growth of the MoSe2 / WSe2 lateral heterojunction on the SiO2 / Si substrate. Figure 12 The image shows the Raman mapping of the MoSe2 / WSe2 lateral heterojunction after aluminum powder-catalyzed CVD growth in this embodiment of the invention. The Raman shift in Figure (a) is 240 cm⁻¹. -1 The Raman shift in Figure (b) is 250 cm. -1 These peaks correspond to the characteristic peaks of MoSe2 and WSe2, respectively. The obvious spatial distribution difference between the MoSe2 and WSe2 regions in the Raman signal indicates that the MoSe2 / WSe2 lateral heterojunction interface is clear and the composition is uniformly distributed. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals.

[0017] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagrams, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0018] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0019] This invention employs the following technical solution: a method for growing MoSe2 / WSe2 lateral heterojunction nanosheets using aluminum powder catalyzed CVD, the method being as follows: S1: The SiO2 / Si wafer was ultrasonically cleaned for 10 minutes each with acetone, alcohol, and deionized water to remove organic matter and contaminants from the surface. After drying, it was treated with a UV cleaner for 5 minutes to enhance its surface hydrophilicity. The SiO2 / Si wafer treated in the above manner was then used as a growth substrate. S2: Anhydrous sodium tungstate and anhydrous sodium molybdate are dissolved in deionized water to serve as precursor solutions for tungsten and molybdenum sources, respectively, and then spin-coated onto a SiO2 / Si wafer. Specifically, appropriate amounts of anhydrous sodium tungstate and anhydrous sodium molybdate are dissolved in deionized water to form tungsten and molybdenum source precursor solutions, respectively, for the growth of WSe2 and MoSe2; appropriate amounts of anhydrous sodium tungstate and anhydrous sodium molybdate are also dissolved in deionized water to form a precursor mixture, which is used for the growth of MoSe2 / WSe2 lateral heterojunctions. The above three precursor solutions are then spin-coated onto the SiO2 / Si wafer using a spin coater at 3000 rpm / s for 30 seconds. S3: Using chemical vapor deposition, selenium powder and SiO2 / Si wafers spin-coated with precursor solutions were placed in a two-temperature zone tube furnace to grow WSe2, MoSe2 and MoSe2 / WSe2 lateral heterojunctions, respectively.

[0020] In one embodiment: Sample placement and temperature control in the tube furnace during growth: Selenium powder was placed in an alumina quartz boat within the first temperature zone of the tube furnace, upstream of the gas flow. The temperature was increased from room temperature to 400°C over 20 minutes and held for 15–20 minutes. 30 mg of aluminum powder was placed in another quartz boat. A SiO2 / Si wafer, spin-coated with the precursor solution facing the aluminum powder, was placed in the quartz boat, which was then placed in the second temperature zone, downstream of the gas flow. For WSe2 growth, the temperature was increased from room temperature to 900–950°C over 20 minutes and held for 15–20 minutes. For MoSe2 growth, the temperature was increased from room temperature to 850°C over 20 minutes and held for 20 minutes. For MoSe2 / WSe2 lateral heterojunction growth, the temperature was increased from room temperature to 900–950°C over 20 minutes and held for 15–20 minutes. The above growth process involves introducing argon gas at a flow rate of 80 sccm. After the growth is complete, the temperature is allowed to drop naturally to 500-600℃, and then the chamber is opened to cool down to room temperature.

[0021] To ensure product quality, the SiO2 / Si substrate grown in S1 is cleaned with acetone, alcohol and deionized water for 10 minutes. After cleaning, the SiO2 / Si substrate is then treated with a UV cleaner for 5 minutes to enhance its hydrophilicity.

[0022] In the precursor solution, anhydrous sodium tungstate and sodium molybdate are dissolved in deionized water to form a mixed solution as tungsten source and molybdenum source, respectively. The tungsten source and molybdenum source are then spin-coated onto the SiO2 / Si substrate in solution form.

[0023] In practical applications, the SiO2 / Si wafer is 1cm×1cm in size, and 30mg of aluminum powder is used as a catalyst to catalyze the growth of MoSe2 / WSe2 lateral heterojunction. The SiO2 / Si wafers with the precursor solution side facing the aluminum powder are placed in a quartz boat. The distance between the quartz boats containing selenium powder and aluminum powder is about 13-14 cm. The quartz boat containing aluminum powder is located in the middle of the second temperature zone. Before the growth begins, argon gas is used for purging at a gas flow rate of 300 sccm for 30 min.

[0024] In specific implementation of this invention, the temperature control of the two temperature zones in the two-zone tube furnace during the growth process is as follows: In the first temperature zone, the temperature is increased from 25°C to 400°C over 20 minutes and held for 15 minutes; in the second temperature zone, when growing WSe2, the temperature is increased from room temperature to 900–950°C over 20 minutes and held for 15–20 minutes; when growing MoSe2, the temperature is increased from room temperature to 850°C over 20 minutes and held for 20 minutes; when growing MoSe2 / WSe2 lateral heterojunctions, the temperature is increased from room temperature to 900–950°C over 20 minutes and held for 15–20 minutes. Argon gas is introduced throughout the growth process at a flow rate of 80 sccm.

[0025] The two-temperature zone tube furnace used in this invention is OTF-1200X-II, manufactured by Shenzhen Kejing Zhida Technology Co., Ltd.

[0026] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0027] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0028] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for CVD growth of MoSe2 / WSe2 lateral heterojunction nanosheets catalyzed by aluminum powder, characterized in that: Includes the following steps: S1: Used as a growth substrate after pretreatment of SiO2 / Si wafer; S2: Spin-coat a precursor solution containing molybdenum and tungsten sources onto the surface of the growth substrate; S3: The growth substrate obtained in S2 is placed together with aluminum powder and selenium powder in a two-temperature zone tube furnace, wherein: The substrate and aluminum powder are placed together in the second temperature zone of the tube furnace, while the selenium powder is placed in the first temperature zone; The substrate is coated with a precursor facing the aluminum powder. S4: In an inert atmosphere, heat the first temperature zone to 400℃ while simultaneously heating the second temperature zone to 900-950℃ to grow MoSe2 / WSe2 lateral heterojunction nanosheets.

2. The method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD according to claim 1, characterized in that: The pretreatment in S1 includes sequential ultrasonic cleaning with acetone, ethanol and deionized water, followed by UV cleaning to enhance hydrophilicity.

3. The method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD according to claim 1, characterized in that: In the precursor solution of S2, the molybdenum source is anhydrous sodium molybdate, and the tungsten source is anhydrous sodium tungstate. After being dissolved in deionized water, the solutions are spin-coated at 3000 rpm for 30 seconds.

4. The method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD according to claim 1, characterized in that: In S3, the amount of aluminum powder used is 30 mg, and in S4, the inert atmosphere is argon gas with a gas flow rate of 80 sccm.

5. The method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD according to claim 4, characterized in that: In S4, the first temperature zone is heated to 400°C for 20 minutes and held for 15 minutes. The second temperature zone is heated to 900-950℃ for 20 minutes and held for 15-20 minutes. After growth, the temperature is allowed to drop naturally to 500-600℃ before the tubular furnace cavity is opened to cool to room temperature.

6. The method for growing MoSe2 / WSe2 lateral heterojunction nanosheets by aluminum powder catalysis CVD according to claim 2, characterized in that: The SiO2 / Si sheet in S1 has a size of 1cm × 1cm; Acetone, ethanol and deionized water were each ultrasonically cleaned for 10 minutes, and then treated with UV cleaning machine for 5 minutes.

7. A MoSe2 / WSe2 transverse heterojunction nanosheet, prepared by the method according to any one of claims 1 to 6, characterized in that: The nanosheet is formed by the lateral connection of MoSe2 and WSe2 regions in the same plane, with a clear and continuous interface and no edge defects caused by hydrogen etching.

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