A method for growing double-layer two-dimensional materials using cadmium sulfide as a sulfur source

Abstract

The present invention provides a method for growing a double-layer two-dimensional material using cadmium sulfide as a sulfur source. The preparation method comprises: subjecting a transition metal source to a chemical vapor deposition reaction with cadmium sulfide powder in a protective gas, and controlling the temperature during deposition to 700-850°C to prepare a double-layer transition metal chalcogenide with AA stacking and AB stacking on the surface of a growth substrate. The size of the double-layer transition metal chalcogenide is 10-100 μm and the thickness is 1 to 3 nm. The present invention proposes for the first time the use of cadmium sulfide powder of a single sulfur molecule as a sulfur source for chemical vapor deposition growth of a double-layer two-dimensional material with a controllable stacking mode. The method of the present invention is simple and easy to operate, the process is controllable, the resulting material has a good morphology, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional semiconductor material preparation, and relates to a method for growing a double-layer two-dimensional material using cadmium sulfide as a sulfur source. Background Art

[0002] With Moore's Law facing a major bottleneck, new materials are urgently needed to replace silicon CMOS technology to achieve high-speed, low-energy information technology. This is where two-dimensional materials come into the spotlight. Graphene, a typical two-dimensional material, possesses extremely high carrier mobility and many other excellent properties, including high thermal conductivity, high mechanical strength, large specific surface area, and broadband light absorption. These properties have also prompted extensive research on other graphene-like two-dimensional materials, including hexagonal boron nitride (h-BN), two-dimensional transition metal dichalcogenides (TMDCs), black phosphorene, silicene, and germanene. TMDCs are a new class of two-dimensional materials, where M is a transition metal atom (such as Mo or W) and X is a chalcogen atom (such as S, Se, or Te). TMDCs possess unique atomic-scale thickness, tunable band gaps, strong spin-orbit coupling, and excellent electronic and mechanical properties. They are widely used in electronics, spintronics, optoelectronics, flexible electronics, and biomolecular detection.

[0003] The interactions between layers in bilayer two-dimensional materials can produce novel material properties. For example, bilayer graphene exhibits superconductivity at a magic angle (1.1°), the conductivity of h-BN is related to its stacking structure, and the band gap of bilayer TMDCs is also affected by their stacking structure. Mechanical exfoliation is generally an ideal method for preparing high-quality bilayer materials, but this method is not suitable for large-scale production, and it is difficult to control the number and size of layers. Chemical vapor deposition is a method that can control the morphology and large-scale growth of high-quality and large-area two-dimensional materials. Currently, bilayer TMDCs are also commonly prepared using chemical vapor deposition. The number of layers in the 2D TMDCs (single, double, or multilayer) can be controlled by adjusting the heating temperature of the metal source or the substrate placement strategy. However, there are few reports on the control of the stacking structure of bilayer TMDCs. The main reason is that the thermodynamic energies of bilayer TMDCs with different stacking structures are similar, making precise control difficult. Therefore, the preparation of bilayer TMDCs with tunable stacking structure has become a research priority. Summary of the Invention

[0004] In response to the above-mentioned problems, the present invention aims to provide a method for growing a two-dimensional material with a controllable double-layer stacking structure using cadmium sulfide as a sulfur source. By chemical vapor deposition reaction of a transition metal source and cadmium sulfide in a protective gas, a double-layer transition metal chalcogenide compound with a controllable stacking structure is prepared on the surface of a growth substrate. The grown sample exhibits AA and AB stacking. The method is simple to operate and the process is controllable. The material has good morphology and has broad application prospects.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for growing a double-layer two-dimensional material using cadmium sulfide as a sulfur source. The method comprises chemical vapor deposition of a transition metal source and cadmium sulfide powder in a protective gas, and preparing AA-stacked and AB-stacked double-layer transition metal chalcogenides on the surface of a growth substrate by controlling the deposition temperature at 700-850°C.

[0006] In one embodiment of the present invention, a double-layer transition metal chalcogenide with AA stacking is prepared on the surface of a growth substrate by controlling the temperature during deposition to be between 790° C. and 840° C.

[0007] In one embodiment of the present invention, a double-layer transition metal chalcogenide with AB stacking is prepared on the surface of a growth substrate by controlling the temperature during deposition to 800-850°C.

[0008] In one embodiment of the present invention, the transition metal source includes any one of a molybdenum source, a tungsten source, a niobium source, and a titanium source.

[0009] In one embodiment of the present invention, the molybdenum source includes at least one of elemental molybdenum, molybdenum trioxide, ammonium molybdate, and sodium molybdate, and the tungsten source includes at least one of elemental tungsten, tungsten trioxide, ammonium tungstate, and sodium tungstate.

[0010] In one embodiment of the present invention, when preparing an AA-stacked double-layer molybdenum disulfide, the temperature during deposition is controlled at 790°C, and when preparing an AB-stacked double-layer molybdenum disulfide, the temperature during deposition is controlled at 800°C.

[0011] In one embodiment of the present invention, when preparing an AA-stacked double-layer tungsten disulfide, the temperature during deposition is controlled at 840°C, and when preparing an AB-stacked double-layer tungsten disulfide, the temperature during deposition is controlled at 850°C.

[0012] In one embodiment of the present invention, the growth substrate includes any one of Si / SiO2, sapphire, mica, and glass.

[0013] In one embodiment of the present invention, the growth substrate is a 300nm SiO2 / Si substrate.

[0014] In one embodiment of the present invention, the protective gas includes any one of an oxidizing atmosphere, a reducing atmosphere and an inert atmosphere; the oxidizing atmosphere includes a mixture of argon and oxygen or a mixture of nitrogen and oxygen, the reducing atmosphere includes a mixture of argon and hydrogen or a mixture of nitrogen and hydrogen, the inert atmosphere is argon or nitrogen, and the amount of the protective gas introduced is 5 to 100 sccm.

[0015] In one embodiment of the present invention, the protective gas is a mixture of argon and hydrogen, the volume ratio of argon to hydrogen in the mixture is 4:1, and the flow rate of the mixture is 50 sccm.

[0016] In one embodiment of the present invention, the chemical vapor deposition reaction is carried out in a tube furnace, the reaction temperature in the center area of ​​the tube furnace is 700-850°C, the reaction time is 1-15 minutes, and the heating rate is 10-40°C / min.

[0017] In one embodiment of the present invention, the cadmium sulfide is placed in an upstream area 5 to 8 cm away from the central area of ​​the tube furnace, and the substrate and the transition metal source are placed in the central area of ​​the tube furnace.

[0018] In one embodiment of the present invention, the transition metal source is disposed on the substrate.

[0019] In one embodiment of the present invention, the transition metal source is attached to the substrate by coating a dispersion of the transition metal source on the substrate and drying the dispersion.

[0020] The tube furnace used in this invention is a conventional tube furnace, with the heating element located in the middle section. Therefore, the area corresponding to the heating element in the tube furnace is defined as the central region, while the upstream region refers to the location upstream in the direction of airflow. When using a tube furnace, the temperature of the chemical vapor deposition process is controlled by controlling the temperature of the central region. The surrounding areas, radiated by the central heat, maintain a constant temperature, with the temperature decreasing as they are further away.

[0021] In one embodiment of the present invention, the method comprises the following steps:

[0022] (1) Cadmium sulfide powder was placed in a tube furnace 6 cm upstream of the central area, and a 300 nm SiO2 / Si growth substrate and a transition metal source were placed together in the central area of ​​the tube furnace;

[0023] (2) A protective gas, argon, is introduced into the tube furnace described in step (1) at a rate of 50 sccm, and a chemical vapor deposition reaction occurs in the tube furnace. The central region is heated to 790-840°C at a rate of 40°C / min and reacted for 10 minutes to obtain a two-dimensional double-layer transition metal sulfide nanomaterial with an AA stacking structure on the substrate surface.

[0024] In one embodiment of the present invention, the method comprises the following steps:

[0025] (1) Cadmium sulfide powder was placed in the upstream area 6 cm from the central area of ​​the tube furnace, and a 300 nm SiO2 / Si growth substrate and a transition metal source were placed together in the central area of ​​the tube furnace;

[0026] (2) A protective gas, argon, is introduced into the tube furnace described in step (1) at a rate of 50 sccm, and a chemical vapor deposition reaction occurs in the tube furnace. The temperature in the central region is raised to 800-850°C at a rate of 40°C / min and the reaction is carried out for 10 minutes to obtain a two-dimensional double-layer transition metal sulfide nanomaterial with an AB stacking structure on the substrate surface.

[0027] The present invention also discloses a double-layer two-dimensional material prepared using the above method. The double-layer two-dimensional material has a size of 10-100 μm and a thickness of 1-3 nm. The double-layer two-dimensional material has an AA or AB stacking method.

[0028] The present invention also discloses a use of the double-layer two-dimensional material in the fields of electronic devices, optical devices and sensors.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention uses any one of Si / SiO2, sapphire, mica, and glass as a substrate, places a transition metal source and cadmium sulfide as a sulfur source in a tube furnace, and prepares a double-layer two-dimensional material by chemical vapor deposition. The stacking method of the grown double-layer two-dimensional material can be controlled to AA or AB stacking.

[0031] (2) The tubular furnace used in the present invention has different temperatures at different distances from the central region, which can meet the temperature requirements of cadmium sulfide. After being heated and volatilized, the cadmium sulfide enters the central region of the tubular furnace along with the protective gas, where it reacts with the transition metal source on the substrate in the central region, forming a double-layer two-dimensional material with both AA and AB stacking on the surface of the growth substrate.

[0032] (3) The present invention proposes for the first time the use of cadmium sulfide powder with a single sulfur molecule as a sulfur source to chemical vapor deposition to grow a double-layer two-dimensional material with a controllable stacking method. This may be attributed to the fact that cadmium sulfide provides a single sulfur molecule to increase the reactivity of the sulfur source. The method of the present invention is simple and easy to operate, the process is controllable, the obtained material has good morphology, and excellent optical, electrical and other properties, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the preparation process of the double-layer two-dimensional material of the present invention;

[0034] Figure 2 2 is a microscopic growth diagram of double-layer MoS2 prepared in Example 1 and Example 2 of the present invention on a Si / SiO2 substrate;

[0035] Figure 3 1 is the Raman spectrum corresponding to MoS2 with different stacking structures prepared in Example 1 and Example 2;

[0036] Figure 4 1 is the photoluminescence spectrum corresponding to MoS2 with different stacking structures prepared in Example 1 and Example 2;

[0037] Figure 5 This is a microscopic image of the growth of double-layer WS2 prepared in Examples 3 and 4 of the present invention on a Si / SiO2 substrate;

[0038] Figure 6 These are the Raman spectra corresponding to WS2 with different stacking structures prepared in Examples 3 and 4.

[0039] Figure 7 These are the photoluminescence spectra corresponding to WS2 with different stacking structures prepared in Example 3 and Example 4. DETAILED DESCRIPTION

[0040] To better illustrate the present invention and facilitate understanding of the technical solution, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0041] Example 1

[0042] A method for growing a double-layer MoS2 using cadmium sulfide as a sulfur source comprises the following steps:

[0043] (1) 50 mg of sodium molybdate was mixed with 100 ml of deionized water and then dropped onto a Si / SiO2 substrate. The substrate was spin-coated at 1000 rpm for 10 seconds and then at 3000 rpm for 30 seconds. The substrate was dried and placed in the center of a tube furnace. 20 mg of cadmium sulfide was placed in the upstream area of ​​the tube furnace 6 cm away from the center. The preparation process is as follows: Figure 1 shown.

[0044] (2) An argon / hydrogen mixed gas (the volume ratio of argon to hydrogen is 4:1) is introduced into the tubular furnace described in step (1) at a rate of 20 sccm, the temperature of the upstream region is maintained at 650°C, and the central region is heated to 790°C at a heating rate of 40°C / min and kept at this temperature for 15 minutes. After the reaction is completed, the mixture is naturally cooled to obtain MoS2 with AA stacking on the Si / SiO2 substrate.

[0045] Example 2

[0046] The difference between Example 2 and Example 1 is that in step (2), the central area is heated to 800°C at a heating rate of 40°C / min, kept warm for 15 minutes, and naturally cooled after the reaction is completed, and MoS2 with AB stacking can be obtained on the Si / SiO2 substrate.

[0047] The AA stacking and AB stacking MoS2 prepared in Examples 1 and 2 were tested under an optical microscope. Their morphologies are as follows: Figure 2 As shown, the feasibility of the present invention to prepare double-layer two-dimensional materials with AA stacking and AB stacking by using cadmium sulfide as the sulfur source is proved. Raman tests and photoluminescence tests were performed on the double-layer region and single-layer region of AA stacking and AB stacking MoS2 materials, respectively, and the results were as follows: Figure 3 and Figure 4 , from the Raman test results of E 2g Peak and A 1g The peak positions of the photoluminescence test and the peaks can prove that the obtained material is MoS2.

[0048] Example 3

[0049] (1) 50 mg of sodium tungstate was mixed with 100 ml of deionized water and dropped onto a Si / SiO2 substrate. The mixture was spin-coated at 1000 rpm for 10 seconds and then at 3000 rpm for 30 seconds. The substrate was dried and placed in the center of a tube furnace. 50 mg of cadmium sulfide was placed in the upstream area of ​​the tube furnace 6 cm away from the center. The preparation process is as follows: Figure 1 shown.

[0050] (2) An argon / hydrogen mixed gas (the volume ratio of argon to hydrogen is 4:1) is introduced into the tubular furnace described in step (1) at a rate of 50 sccm, the temperature of the upstream area is maintained at 600°C, and the central area is heated to 840°C at a heating rate of 40°C / min and kept at this temperature for 15 minutes. After the reaction is completed, the mixture is naturally cooled to obtain WS2 with AA stacking on the Si / SiO2 substrate.

[0051] Example 4

[0052] The difference between Example 4 and Example 3 is that in step (2), the central area is heated to 850°C at a heating rate of 40°C / min, kept warm for 15 minutes, and naturally cooled after the reaction is completed, and WS2 with AB stacking can be obtained on the Si / SiO2 substrate.

[0053] The AA stacking and AB stacking WS2 prepared in Examples 3 and 4 were tested under an optical microscope. Their morphologies are shown in Figure 2. Figure 4 As shown, the feasibility of the present invention to prepare double-layer two-dimensional materials with AA stacking and AB stacking by using cadmium sulfide as the sulfur source is proved. Raman test and photoluminescence test were performed on the double-layer area and single-layer area of ​​AA stacking and AB stacking WS2 materials respectively. Figure 5 , from the Raman test results of E 2g Peak and A 1g The peak positions of the peaks and photoluminescence tests can prove that the obtained material is WS2.

[0054] Based on the above embodiments, it can be concluded that the present invention can generate the required double-layer stacking structure by growing a double-layer two-dimensional material using cadmium sulfide as a sulfur source, and has broad application prospects in the fields of electronic devices, optical devices, sensors, etc.

[0055] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for growing a double-layer two-dimensional material using cadmium sulfide as a sulfur source, characterized in that: The method comprises: subjecting a transition metal source and cadmium sulfide powder to a chemical vapor deposition reaction in a protective gas, and preparing an AA-stacked or AB-stacked double-layer transition metal chalcogenide on the surface of a growth substrate by controlling the temperature during deposition at 700-850° C.; preparing an AA-stacked double-layer transition metal chalcogenide on the surface of a growth substrate by controlling the temperature during deposition at 790-840° C.; and preparing an AB-stacked double-layer transition metal chalcogenide on the surface of a growth substrate by controlling the temperature during deposition at 800-850° C.

2. The method according to claim 1, characterized in that The transition metal source includes a molybdenum source and a tungsten source; wherein the molybdenum source includes at least one of elemental molybdenum, molybdenum trioxide, ammonium molybdate, and sodium molybdate; and the tungsten source includes at least one of elemental tungsten, tungsten trioxide, ammonium tungstate, and sodium tungstate.

3. The method according to claim 1, characterized in that The chemical vapor deposition reaction is carried out in a tube furnace, the reaction temperature in the center area of ​​the tube furnace is 700-850° C., the reaction time is 1-15 minutes, and the heating rate is 40° C. / min.

4. The method according to claim 1, wherein The cadmium sulfide powder is placed in an upstream area 5-8 cm away from the central area of ​​the tube furnace, and the substrate and the transition metal source are placed in the central area of ​​the tube furnace.

5. The method according to claim 1, wherein The growth substrate includes any one of SiO2 / Si, sapphire, mica, and glass.

6. The method according to claim 1, wherein The protective gas includes any one of an oxidizing atmosphere, a reducing atmosphere and an inert atmosphere; the oxidizing atmosphere includes a mixture of argon and oxygen or a mixture of nitrogen and oxygen, the reducing atmosphere includes a mixture of argon and hydrogen or a mixture of nitrogen and hydrogen, the inert atmosphere is argon or nitrogen, and the flow rate of the protective gas is 5 to 100 sccm.

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