Preparation method of multiple transverse superlattice structure of transition metal chalcogenide

Abstract

The invention belongs to the technical field of two-dimensional material preparation, and discloses a preparation method of a multiple transverse superlattice structure of a transition metal chalcogenide. The preparation method comprises the following steps: by taking a polycrystalline gold foil as a substrate, putting the substrate, a transition metal oxide and a selenium elementary substance into a normal-pressure chemical vapor deposition system; the substrate and the transition metal oxide are heated to 780-950 DEG C, the selenium simple substance is heated to 300-500 DEG C, and then heat preservation growth is carried out; after the thermal insulation growth is finished, cooling the substrate to 300-750 DEG C, repeating the growth process for at least one time, cooling the substrate to 300-750 DEG C before repeating the growth process each time, and cooling after the growth is finished, so as to obtain a finished product. The preparation method provided by the invention can be used for stably and repeatedly preparing a high-quality and large-area superlattice structure of the transition metal chalcogenide; and the preparation device is simple, low in cost, good in repeatability, high in expansibility and easy to popularize and apply.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional material preparation, and specifically relates to a method for preparing a multiple lateral superlattice structure of a transition metal chalcogenide compound. Background Art

[0002] In recent years, the number of transistors in integrated circuits has continued to increase, and the manufacturing size of transistors has continued to shrink, gradually approaching the physical limit of silicon materials, and the short channel effect has become more and more obvious. With the increasing requirements of microelectronics technology for integration and functionality, two-dimensional materials have attracted more and more attention from researchers at home and abroad. Compared with zero-bandgap graphene, transition metal chalcogenides have broad application prospects in many fields such as transistors and optoelectronic devices due to their tunable bandgap and high carrier mobility. Among them, two-dimensional heterojunctions of transition metal chalcogenides have great application potential in low-power, high-performance and flexible electro-optical devices, such as transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated by van der Waals stacking of different two-dimensional materials, in-situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition metal chalcogenide lateral heterostructures have been synthesized by single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control the growth of a single domain in situ. Two or more semiconductor materials grow alternately and periodically to form a superlattice structure. Superlattice structures can be divided into lateral superlattice and vertical superlattice. The research on the growth of superlattice materials has been slow, there are few preparation methods, and the preparation conditions are harsh and complex. Most of the current technologies use expensive and complex organic metal chemical vapor deposition systems and molecular beam epitaxy systems, which are not conducive to the development of research and application. Therefore, it is necessary to propose a simple method for preparing superlattice structures to promote the research and application of superlattice. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preparing a multiple lateral superlattice structure of a transition metal chalcogenide. The preparation method provided by the present invention can realize a simple and efficient preparation of a superlattice structure of a transition metal chalcogenide.

[0004] The invention provides a method for preparing a multiple lateral superlattice structure of a transition metal chalcogenide compound.

[0005] Specifically, a method for preparing a multiple lateral superlattice structure of a transition metal chalcogenide comprises the following steps:

[0006] (1) annealing the gold foil to obtain a polycrystalline gold foil;

[0007] (2) using the polycrystalline gold foil prepared in step (1) as a substrate, placing the substrate, transition metal oxide, and selenium in a normal pressure chemical vapor deposition system;

[0008] (3) After introducing hydrogen and argon, the substrate and the transition metal oxide are heated to 780-950° C., the selenium element is heated to 300-500° C., and then the growth is maintained at this temperature;

[0009] (4) After the heat preservation growth is completed, the substrate is cooled to 300-750° C., and the growth process of step (3) is repeated at least once. Before each repetition of step (3), the substrate is cooled to 300-750° C. and cooled after the growth is completed to obtain a multiple lateral superlattice structure of a transition metal sulfide compound.

[0010] Preferably, in step (1), the annealing temperature is 850°C-1040°C, and the annealing time is 3-10 hours; further preferably, in step (1), the annealing temperature is 900°C-1000°C, and the annealing time is 4-8 hours. The present invention uses gold foil as the substrate growth material, and only uses the simplest annealing treatment to make the original polycrystalline, small-grained gold foil become a stable polycrystalline gold foil with large crystal domains and atomic-level flat interfaces. It is used for the growth of transition metal chalcogenide materials, and can form high-quality, large-area multiple lateral superlattice structures on its surface.

[0011] Preferably, in step (2), the transition metal oxide includes molybdenum oxide and tungsten oxide; further preferably, the transition metal oxide is molybdenum oxide and tungsten oxide.

[0012] Preferably, the mass ratio of the molybdenum oxide to the tungsten oxide is 1:(1.5-3); further preferably, the mass ratio of the molybdenum oxide to the tungsten oxide is 1:(2-3), such as 1:2, 3:7, 3:8, 1:3, etc.

[0013] Preferably, in step (2), the mass ratio of the transition metal oxide to the selenium element is (1-6): (250-5000); further preferably, in step (2), the mass ratio of the transition metal oxide to the selenium element is (3-6): (1000-3000); more preferably, in step (2), the mass ratio of the transition metal oxide to the selenium element is (3-6): (1000-2000).

[0014] Preferably, in step (2), the transition metal oxide is placed 0.5-5 cm upstream of the substrate; and the selenium element is placed 8-20 cm upstream of the substrate.

[0015] It should be noted that the atmospheric pressure chemical vapor deposition system described in the present invention is a conventional deposition system in the art and has nothing special thereto. The use of an ordinary, conventional atmospheric pressure chemical vapor deposition system has a low cost and is easy to promote and apply.

[0016] Preferably, in step (3), the flow rate of the argon gas is 40-120 sccm, and the flow rate of the hydrogen gas is 0.5-10 sccm, wherein sccm is a unit of volume flow rate, i.e., standard milliliters per minute.

[0017] Preferably, in step (3), the substrate and the transition metal oxide are heated to 780-950° C., the selenium element is heated to 300-450° C., and then the growth is maintained at this temperature.

[0018] Preferably, in step (3), the time of the heat preservation growth is 2-5 minutes.

[0019] Preferably, in step (4), after the thermal insulation growth is completed, the substrate is cooled to 300-750°C; further preferably, in step (4), after the thermal insulation growth is completed, the substrate is cooled to 400-650°C; more preferably, in step (4), after the thermal insulation growth is completed, the substrate is cooled to 450-600°C.

[0020] Preferably, in step (4), the growth process of step (3) is repeated 1-4 times. When repeated once, a double lateral superlattice structure is formed on the substrate; when repeated twice, a triple lateral superlattice structure is formed on the substrate; when repeated three times, a quadruple lateral superlattice structure is formed on the substrate, and so on. The multiple lateral superlattice structures in the present invention include double and more lateral superlattice structures.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention uses polycrystalline gold foil as a substrate, utilizes the strong force of gold atoms on transition metal chalcogenides, and rapidly cools down and restarts the growth to repeatedly prepare a superlattice structure of transition metal chalcogenides. This is a simple and efficient strategy for preparing a superlattice structure of transition metal chalcogenides. The present invention can stably and repeatedly prepare a high-quality, large-area superlattice structure of transition metal chalcogenides.

[0023] (2) The preparation method provided by the present invention has a simple preparation device and low cost. Compared with the method of preparing lateral superlattices using a commonly used expensive and environmentally unfriendly organic metal chemical vapor deposition system, this invention only needs to use the simplest, most common, and ordinary atmospheric pressure chemical vapor deposition system, which is low in cost and easy to promote and apply.

[0024] (3) The preparation method provided by the present invention has good repeatability and strong scalability. The entire preparation process is simple and convenient, and the preparation is rapid. It can easily and repeatedly prepare a lateral superlattice structure in which multiple transition metal sulfide compounds are alternately arranged. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An optical microscope image of the double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 1;

[0026] Figure 2 A Raman signal scanning diagram of the double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 1;

[0027] Figure 3 The Raman characteristic peak of tungsten diselenide in the double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 1;

[0028] Figure 4 It is the Raman characteristic peak of molybdenum diselenide in the double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 1;

[0029] Figure 5 An optical microscope image of a double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 1 transferred onto silicon dioxide;

[0030] Figure 6 This is an atomic force microscope (AFM) scan of the polycrystalline gold foil after annealing in Comparative Example 1;

[0031] Figure 7 An optical microscope image of a molybdenum diselenide / tungsten diselenide lateral heterojunction prepared in Comparative Example 1;

[0032] Figure 8 This is a Raman signal scanning diagram of the molybdenum diselenide / tungsten diselenide lateral heterojunction prepared in Comparative Example 1;

[0033] Fig. 9 An optical microscope image of a triple lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 2;

[0034] Fig.10 A Raman signal scanning diagram of the triple lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 2;

[0035] Fig.11An optical microscope image of a triple lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide prepared in Example 2 transferred onto silicon dioxide;

[0036] Fig.12 This is a Raman signal scan of the molybdenum diselenide / tungsten diselenide lateral heterojunction prepared in Comparative Example 2;

[0037] Fig.13 This is a Raman signal scanning diagram of the molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy / molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy structure prepared in Comparative Example 3;

[0038] Fig.14 The Raman characteristic peak of the molybdenum diselenide-tungsten diselenide alloy in the molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy / molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy structure prepared in Comparative Example 3;

[0039] Fig.15 It is the Raman characteristic peak of molybdenum diselenide in the structure of molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy / molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy prepared in Comparative Example 3. DETAILED DESCRIPTION

[0040] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0041] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0042] The following is a detailed explanation taking the preparation of the MoSe / WSe / MoSe / WSe double lateral superlattice structure and the MoSe / WSe / MoSe / WSe / MoSe / WSe / MoSe / WSe triple lateral superlattice as examples.

[0043] Example 1

[0044] A method for preparing a double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide, comprising the following steps:

[0045] (1) Place the purchased 25 mm*25 mm commercial gold foil in a quartz boat and use a muffle furnace for heating and annealing. Heat to 1000°C in air, keep the temperature constant for 4 hours, and then cool naturally to complete annealing, thereby obtaining polycrystalline gold foil.

[0046] (2) Using a common atmospheric pressure chemical vapor deposition system, with annealed polycrystalline gold foil as the substrate, the polycrystalline gold foil is placed in the heating center area of ​​a high-temperature tube furnace, and molybdenum oxide and tungsten oxide powders are mixed in a mass ratio of 3:7 to obtain a mixed powder. 10 mg of the mixed powder is placed 1 cm upstream of the substrate gold foil, and 3 g of selenium is placed 15 cm upstream from the substrate.

[0047] (3) 100 sccm of argon and 2 sccm of hydrogen were introduced into the atmospheric pressure chemical vapor deposition system, and the selenium element, substrate, and mixed powder were heated to 400° C., 850° C., and 850° C., respectively, and the temperature was maintained at that temperature for 3 minutes.

[0048] (4) After the reaction is completed, the heating program of the tubular furnace is automatically terminated, the introduction of hydrogen is stopped, the furnace cover is opened (without taking out the substrate) for rapid cooling, and when the temperature drops to 500°C, the heating program is restarted, the selenium element and the substrate are heated to 400°C and 850°C respectively, 100sccm of argon is introduced, the temperature is kept constant for 3 minutes, and 2sccm of hydrogen is introduced, and the growth is repeated once. After the reaction is completed, the heating program of the tubular furnace is automatically terminated, and when the temperature of the reaction chamber drops to 400°C, the furnace cover is opened for rapid cooling, and when the temperature drops to room temperature, the argon is turned off, and the sample is taken out to obtain a double lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide.

[0049] The optical microscope photo of the obtained MoSe / WSe / MoSe / WSe lateral superlattice structure on the gold foil substrate is shown in Figure 1 As shown, it can be seen that on the gold foil substrate, the MoSe / WSe / MoSe / WSe lateral superlattice structure obtained is difficult to identify, and the domain size is about 20-40 μm.

[0050] By scanning the Raman signal of the MoSe2 / WSe2 / MoSe2 / WSe2 lateral superlattice structure, such as Figure 2 , we can clearly see the lateral superlattice structure of MoSe / WSe / MoSe / WSe. The Raman signals of different materials are different. Figure 1 A continuous image scan of a triangular material can be obtained Figure 2 , Figure 3 Yes Figure 2 Raman signal test in the green area of ​​A, Raman characteristic peak ~250cm -1 , which is tungsten diselenide material. Figure 4 Yes Figure 2 Raman signal test in the blue area of ​​middle B, Raman characteristic peak ~240cm -1 , which is molybdenum diselenide material. Figure 2 A and B together form a Raman scan of a triangular material. Figure 2It can be seen that from the inside to the outside, blue-green-blue-green alternate, indicating that the lateral superlattice structure was successfully prepared.

[0051] The lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide on the gold foil was transferred to silicon dioxide. The specific transfer method is as follows: fix the gold foil with the lateral superlattice structure on a glass slide with tape, spin-coat polymethyl methacrylate (PMMA) at 4000 rpm for 40 seconds, and place it on a heating table at 80°C for 10 minutes after spin coating to allow PMMA to adhere tightly to the material on the gold foil. After heating, place the gold foil in a gold etching solution (50 mg of iodine and 200 mg of potassium iodide dissolved in 100 ml of deionized water). When the gold foil is completely etched, the PMMA film that sticks to the material is left. Pick it up with filter paper and wash it in deionized water for half an hour, then pick it up with silicon dioxide, dry it for a day, and then place it at 130°C for half an hour to allow the material to adhere to the silicon dioxide, and then put it in acetone to remove PMMA. The lateral superlattice structure is successfully transferred to silicon dioxide. The optical microscope photo is shown in the figure. Figure 5 ( Figure 5 The dark and light colors represent two materials. The successful preparation of the lateral superlattice is further verified by transferring the lateral superlattice structure to a silicon wafer.

[0052] Comparative Example 1

[0053] A method for preparing a lateral heterojunction of molybdenum diselenide / tungsten diselenide comprises the following steps:

[0054] (1) Place the purchased 25mm*25mm commercial gold foil in a quartz boat and use a muffle furnace for heating and annealing. Heat to 980℃ in air and keep the temperature constant for 6 hours. Then cool naturally to complete annealing to obtain polycrystalline gold foil. The atomic force microscope photo of the crystal domain area of ​​the obtained polycrystalline gold foil is shown in the figure. Figure 6 As shown, the annealed gold presents a flat surface with a surface roughness of 0.64 nm.

[0055] (2) Using a common atmospheric pressure chemical vapor deposition system, annealed polycrystalline gold foil was used as the substrate to grow a lateral heterojunction of molybdenum diselenide / tungsten diselenide. The gold foil was placed in the heating center of a high-temperature tube furnace, and molybdenum oxide and tungsten oxide powders were mixed in a mass ratio of 3:7 to obtain a mixed powder. 10 mg of the mixed powder was placed 3 cm upstream of the gold foil. 3 g of selenium was placed 15 cm upstream from the substrate.

[0056] (3) 100 sccm of argon and 2 sccm of hydrogen were introduced into the atmospheric pressure chemical vapor deposition system, and the selenium element, substrate, and mixed powder were heated to 400°C, 850°C, and 850°C, respectively, and the temperature was maintained for 3 minutes. After the reaction was completed, the tubular furnace heating program was automatically terminated, and the introduction of hydrogen was stopped. When the temperature of the reaction chamber naturally dropped to 400°C, the furnace cover was opened to quickly cool down. After the temperature dropped to room temperature, the argon was turned off, and the sample was taken out to obtain a lateral heterojunction of molybdenum diselenide / tungsten diselenide.

[0057] The optical microscope photo of the lateral heterojunction of MoSe2 / WSe2 on the gold foil substrate is shown in Figure 7 As shown. It can be seen that on the gold foil substrate, the MoSe / WSe lateral heterojunction is relatively clear, and the heterojunction domain size is about 10-20μm. Raman signal scanning is performed, and the Raman signal scanning diagram is as follows Figure 8 As shown. Figure 8 It can be seen that what is prepared in this comparative example is a lateral heterojunction, not a superlattice structure.

[0058] Example 2

[0059] A method for preparing a triple lateral superlattice structure of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide, comprising the following steps:

[0060] (1) Place the purchased 25 mm*25 mm commercial gold foil in a quartz boat and use a muffle furnace for heating and annealing. Heat to 1020°C in air, keep the temperature constant for 4 hours, and then cool naturally to complete annealing, thereby obtaining a polycrystalline gold foil.

[0061] (2) Using a common atmospheric pressure chemical vapor deposition system, the annealed polycrystalline gold foil is used as the substrate for material growth. The gold foil is placed in the heating center area of ​​a high-temperature tube furnace, and the powders of molybdenum oxide and tungsten oxide are mixed in a mass ratio of 3:7 to obtain a mixed powder. 10 mg of the mixed powder is placed 3 cm upstream of the gold foil, and 3 g of selenium is placed 15 cm upstream from the substrate.

[0062] (3) 100 sccm of argon and 2 sccm of hydrogen were introduced into the atmospheric pressure chemical vapor deposition system, and the selenium element, substrate, and mixed powder were heated to 400°C, 850°C, and 850°C, respectively, and kept at a constant temperature for 3 minutes. After the reaction was completed, the heating program of the tubular furnace was automatically terminated, the introduction of hydrogen was stopped, and the furnace cover was opened (without removing the substrate) for rapid cooling. When the temperature dropped to 600°C, the heating program was restarted, and the selenium element and substrate were heated to 400°C and 850°C, respectively, 100 sccm of argon was introduced, and the temperature was kept constant for 3 minutes, and 2 sccm of hydrogen was introduced, and the growth was repeated for the first time. After the reaction was completed, the heating program of the tubular furnace was automatically terminated, the introduction of hydrogen was stopped, and the furnace cover was opened (without removing the substrate) for rapid cooling. When the temperature dropped to 750°C, the heating program was restarted, and the selenium element and substrate were heated to 400°C and 850°C, respectively, 100 sccm of argon was introduced, and the temperature was kept constant for 3 minutes, and 2 sccm of hydrogen was introduced, and the growth was repeated for the second time. After cooling to room temperature, the sample is taken out, and a triple lateral superlattice of molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide / molybdenum diselenide / tungsten diselenide can be prepared on the gold foil.

[0063] The optical microscope photograph of the lateral superlattice structure of MoSe / WSe / MoSe / WSe / MoSe / WSe on the obtained gold foil substrate is shown in Fig. 9 As shown in Figure 2, the domain size is about 40-60 μm. Raman signal scanning shows that the triple lateral superlattice was successfully prepared. Fig.10 As shown, Fig.10 The orange-red area in the middle A is the Raman signal of tungsten diselenide material in the triple lateral superlattice. Fig.10 The green elongated area in the middle of B is the Raman signal of the molybdenum diselenide material. It is transferred to silicon dioxide according to the transfer method of Example 1, and the triple superlattice structure can be clearly seen, such as Fig.11 As shown, the dark area is molybdenum diselenide material, and the light-colored tungsten diselenide material. From the inside to the outside, the colors change alternately from dark to light-dark-light-dark-light, representing the alternating growth arrangement of molybdenum diselenide-tungsten diselenide-molybdenum diselenide-tungsten diselenide-molybdenum diselenide-tungsten diselenide to form a triple superlattice structure.

[0064] Comparative Example 2

[0065] A method for preparing a lateral heterojunction of repeatedly grown molybdenum diselenide / tungsten diselenide comprises the following steps:

[0066] (1) Place the purchased 25 mm*25 mm commercial gold foil in a quartz boat and use a muffle furnace for heating and annealing. Heat to 1000°C in air, keep the temperature constant for 4 hours, and then cool naturally to complete annealing, thereby obtaining polycrystalline gold foil.

[0067] (2) Using a common atmospheric pressure chemical vapor deposition system, the annealed polycrystalline gold foil is used as the substrate for material growth. The gold foil is placed in the heating center area of ​​a high-temperature tube furnace, and the powders of molybdenum oxide and tungsten oxide are mixed in a mass ratio of 3:7 to obtain a mixed powder. 10 mg of the mixed powder is placed 3 cm upstream of the gold foil, and 3 g of selenium is placed 15 cm upstream from the substrate.

[0068] (3) 100 sccm of argon and 2 sccm of hydrogen are introduced into the atmospheric pressure chemical vapor deposition system, and the selenium element, substrate, and mixed powder are heated to 400°C, 850°C, and 850°C, respectively, and the temperature is maintained for 3 minutes. After the reaction is completed, the tubular furnace heating program is automatically terminated, and the substrate temperature is still maintained at around 850°C. The heating program is quickly started again, and the selenium element and substrate are heated to 400°C and 850°C, respectively. 100 sccm of argon is introduced, and the temperature is maintained for 3 minutes and 2 sccm of hydrogen is introduced. The growth is repeated once. After the growth is completed, the sample is taken out after the temperature naturally drops to room temperature. The structure of the sample is analyzed by optical microscopy. The analysis shows that what grows on the gold foil is still just Fig.12 The MoSe2 / WSe2 lateral heterojunction shown cannot produce a lateral superlattice.

[0069] Comparative Example 3

[0070] A method for preparing a molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy / molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy structure, comprising the following steps:

[0071] (1) Place the purchased 25 mm*25 mm commercial gold foil in a quartz boat and use a muffle furnace for heating and annealing. Heat to 1000°C in air, keep the temperature constant for 4 hours, and then cool naturally to complete annealing, thereby obtaining polycrystalline gold foil.

[0072] (2) Using a common atmospheric pressure chemical vapor deposition system, annealed polycrystalline gold foil was used as a substrate to grow a lateral superlattice of molybdenum diselenide / tungsten diselenide. The gold foil was placed in the heating center area of ​​a high-temperature tube furnace, and molybdenum oxide and tungsten oxide powders were mixed in a mass ratio of 3:7 to obtain a mixed powder. 10 mg of the mixed powder was placed 1 cm upstream of the substrate gold foil, and 3 g of selenium was placed 15 cm upstream from the substrate.

[0073] (3) 100 sccm of argon and 2 sccm of hydrogen were introduced into the atmospheric pressure chemical vapor deposition system, and the selenium element, substrate, and mixed powder were heated to 400° C., 850° C., and 850° C., respectively, and the temperature was maintained at that temperature for 3 minutes.

[0074] (4) After the reaction is completed, the heating program of the tubular furnace is automatically terminated, the introduction of hydrogen is stopped, the furnace cover is opened and the temperature is quickly cooled to room temperature, and then the heating program is restarted. The selenium element and the substrate are heated to 400°C and 850°C respectively, 100sccm of argon is introduced, the temperature is kept constant for 3 minutes, and 2sccm of hydrogen is introduced, and the growth is repeated once. After the reaction is completed, the heating program of the tubular furnace is automatically terminated. When the temperature of the reaction chamber drops to 400°C, the furnace cover is opened to quickly cool down. After the temperature drops to room temperature, the argon is turned off and the sample is taken out. Raman test characterization analysis is performed on the structure of the sample, such as Fig.13 As shown, Fig.14 Yes Fig.13 The Raman signal test corresponding to A in the figure shows that its Raman characteristic peak is at 245cm -1 On the left and right are molybdenum diselenide-tungsten diselenide alloy materials. Fig.15 Yes Fig.13 The Raman signal test corresponding to B in the figure shows that its Raman characteristic peak is at 240cm -1 The left and right are molybdenum diselenide materials. Analysis shows that what grows on the gold foil is a molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy / molybdenum diselenide / molybdenum diselenide-tungsten diselenide alloy structure, and a lateral superlattice structure cannot be prepared.

[0075] From the above embodiments and comparative examples, it can be seen that the preparation method of multiple lateral superlattice structures of transition metal chalcogenides provided by the present invention can make the transition metal chalcogenide heterojunction continue to grow epitaxially on the first grown transition metal chalcogenide heterojunction after rapidly cooling to a specific temperature after the first deposition growth is completed, and then restarting the deposition growth process, so as to obtain a lateral superlattice structure. When the deposition growth is not cooled down after the first deposition growth is completed or the deposition growth process is restarted after cooling to room temperature, the lateral superlattice structure cannot be obtained.

[0076] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a multiple lateral superlattice structure of a transition metal chalcogenide, characterized in that: The following steps are involved: (1) annealing the gold foil to obtain a polycrystalline gold foil; (2) using the polycrystalline gold foil prepared in step (1) as a substrate, placing the substrate, transition metal oxide, and selenium in a normal pressure chemical vapor deposition system; (3) After introducing hydrogen and argon, the substrate and the transition metal oxide are heated to 780-950° C., the selenium element is heated to 300-500° C., and then the growth is maintained at this temperature; (4) After the heat preservation growth is completed, the substrate is cooled to 300-750° C., and the growth process of step (3) is repeated at least once. Before each repetition of step (3), the substrate is cooled to 300-750° C. and cooled after the growth is completed to obtain a multiple lateral superlattice structure of a transition metal sulfide compound.

2. The preparation method according to claim 1, characterized in that: In step (1), the annealing temperature is 850-1040° C. and the annealing time is 3-10 hours.

3. The preparation method according to claim 1, characterized in that: In step (2), the transition metal oxide includes molybdenum oxide and tungsten oxide.

4. The preparation method according to claim 3, characterized in that: The transition metal oxides are molybdenum oxide and tungsten oxide; the mass ratio of the molybdenum oxide to the tungsten oxide is 1:(1.5-3).

5. The preparation method according to any one of claims 1, 3 and 4, characterized in that: In step (2), the mass ratio of the transition metal oxide to the selenium element is (1-6): (250-5000).

6. The preparation method according to claim 1, characterized in that: In step (3), the flow rate of the argon gas is 40-120 sccm, and the flow rate of the hydrogen gas is 0.5-10 sccm.

7. The preparation method according to any one of claims 1, 3 and 4, characterized in that: In step (3), the substrate and the transition metal oxide are heated to 780-950° C., the selenium element is heated to 300-450° C., and then the growth is maintained at this temperature.

8. The preparation method according to claim 7, characterized in that: In step (3), the time of the heat preservation growth is 2-5 minutes.

9. The preparation method according to claim 1 or 8, characterized in that: In step (4), after the heat preservation growth is completed, the substrate is cooled to 300-750°C.

10. The preparation method according to claim 9, characterized in that: In step (4), the growth process of step (3) is repeated 1-4 times.

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