Method for preparing single-layer and single-crystal rhenium disulfide through chemical vapor deposition

Abstract

The invention discloses a method for preparing single-layer and single-crystal rhenium disulfide through chemical vapor deposition, and relates to the field of two-dimensional material preparation, and the method is technically characterized by comprising the steps of raw material preparation, raw material loading, temperature control reaction, sampling ending and the like. According to the method, a space confinement growth space is constructed by utilizing face-to-face stacked substrates, the single-layer single-crystal ReS2 is prepared by adopting a double-temperature-zone tubular furnace quartz tube, the preparation process is simple, easy to operate and controllable, the single-layer ReS2 with uniform thickness and high crystallinity is obtained on the surfaces of various substrates, and controllable preparation of the single-layer single-crystal ReS2 is realized on the surface of magnesium oxide (001).

Description

Technical Field

[0001] The present invention relates to the field of two-dimensional material preparation, and in particular to a method for preparing single-layer single-crystal rhenium disulfide by chemical vapor deposition. Background Art

[0002] Two-dimensional transition metal dichalcogenides (TMDCs) are widely used in optics, electricity, catalysis, energy and other fields due to their physical and chemical properties such as atomic-level thickness, high specific surface area, no dangling bonds on the surface, and interlayer van der Waals forces. Low-symmetry two-dimensional rhenium disulfide (ReS2) is a typical representative of two-dimensional TMDs. It has the characteristics of in-plane anisotropy of physical and chemical properties and semiconductor properties, which makes it have broad development prospects in the fields of electronic devices, photodetectors and electrocatalysis. In order to realize its anisotropy-related applications such as polarized photodetectors and anisotropic logic devices, single crystal preparation is a prerequisite.

[0003] The commonly used preparation methods at present are: mechanical exfoliation, liquid phase exfoliation, chemical vapor transport and chemical vapor deposition (CVD). Compared with other methods, CVD has the advantages of high yield and high quality.

[0004] In the existing CVD method, due to weak interface coupling, easy formation of out-of-plane chemical bonds, and low grain boundary formation energy, the CVD preparation of ReS2 has the following problems: (1) poor experimental repeatability; (2) difficulty in growing a single layer; and (3) difficulty in preparing single crystals.

[0005] To this end, the present invention aims to provide a method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition to solve the above-mentioned problems. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and provide a method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition. The reaction concentration and concentration gradient of the precursor sulfur and the precursor sodium perrhenate are effectively controlled by using a spin coating precursor salt combined with a method of constructing a spatially confined reaction chamber, and the uneven spatial distribution of the product caused by the uneven distribution of the precursor concentration is effectively avoided. At the same time, a relatively wide growth parameter window is obtained, which improves the stability and repeatability of the experiment.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition, comprising the following steps:

[0009] S1. Substrate preparation: prepare a spin coating substrate and a target substrate, spin-coat a sodium perrhenate (NaReO4) solution on the spin coating substrate, place the target substrate on the spin coating substrate, and place the polished surface of the spin coating substrate and the polished surface of the target substrate face to face to form a slit, thereby forming a spatially confined reaction chamber;

[0010] S2. Precursor pretreatment and loading: sulfur powder is placed in a corundum crucible for melting and recrystallization as a sulfur source; a dual-temperature zone tubular furnace quartz tube is prepared, the sulfur source is placed at one end of the quartz tube close to the air inlet, the spatial confinement reaction chamber is placed at one end of the quartz tube close to the air outlet, the air inlet and outlet flanges are sealed, and then a predetermined flow of inert gas is introduced to completely replace the air in the quartz tube;

[0011] S3, control reaction: introduce inert gas, set the center temperature of the high temperature zone of the tube furnace and the center temperature of the low temperature zone of the tube furnace respectively, after heating to the set temperature, adjust the relative position of the quartz tube and the furnace body, align the spatial confined reaction chamber with the center of the high temperature zone of the tube furnace, align the sulfur source container with the center of the low temperature zone of the tube furnace, and the reaction time is 15 to 30 minutes;

[0012] S4. End sampling: continue to introduce inert gas, adjust the quartz tube away from the heating position of the furnace to quickly cool the quartz tube, adjust the flow rate of the inert gas during the cooling process, and after the quartz tube cools to room temperature, take out the spatially confined reaction chamber to obtain a single layer of ReS2 on the surface of the target substrate.

[0013] Furthermore, in S1, the spin-coating substrate is c-plane sapphire, and the material of the target substrate is one of c-plane sapphire, a-plane sapphire, strontium titanate (001), and magnesium oxide (001).

[0014] Furthermore, in S1, the spin-coated substrate was subjected to oxygen plasma treatment for 50 s before spin-coating the NaReO4 solution, and the power was set to 50W.

[0015] Furthermore, in S1, the concentration of the NaReO4 solution is 0.0025-0.05 mol / L.

[0016] Furthermore, in S1, the amount of the NaReO4 solution added during spin coating is 20 to 50 μL / cm2.

[0017] Furthermore, in S1, the spin-coated substrate is placed on a spin coater, and the NaReO4 solution is sucked by a pipette and dripped onto the surface of the spin-coated substrate; the rotation speed of the spin coater is 500 to 5000 rpm, and the spin coating time is 30 to 50 s.

[0018] Furthermore, in S2, sulfur powder is loaded into a corundum crucible and heated to 120°C to 140°C using a hot plate to melt and then cooled to room temperature for recrystallization.

[0019] Furthermore, in S2, the sulfur source is in excess during the reaction; the predetermined flow rate of the inert gas is 100 to 200 sccm, the introduction time is 15 to 30 minutes, and the inert gas is argon.

[0020] Furthermore, in S3, the flow rate of the inert gas is 40 to 60 sccm, the introduction time is 15 to 30 min, and the inert gas is argon.

[0021] Furthermore, in S3, the central temperature of the high temperature zone of the tube furnace is 800-880°C, and the heating rate is 20-40°C / min; the central temperature of the low temperature zone of the tube furnace is 140-180°C, and the heating rate is 10-20°C / min;

[0022] Furthermore, in S4, the flow rate of the inert gas is adjusted to 200 sccm during the cooling process of the quartz tube.

[0023] Furthermore, in S4, the obtained single-layer ReS2 grain size is 7 to 20 μm.

[0024] Furthermore, in S4, when magnesium oxide (001) is used as the target substrate, the obtained single-layer ReS2 grains are single crystals.

[0025] Compared with the prior art, this solution has the following beneficial effects:

[0026] 1. The present invention adopts a method of spin coating precursor salt combined with constructing a spatially confined reaction chamber to effectively control the reaction concentration and concentration gradient of the precursor sulfur and the precursor sodium perrhenate, effectively avoiding the uneven spatial distribution of the product caused by the uneven distribution of the precursor concentration; at the same time, a relatively wide growth parameter window is obtained, which improves the stability and repeatability of the experiment;

[0027] 2. In the present invention, the oxygen plasma pre-treats the spin-coated substrate, making the spin-coated substrate hydrophilic, so that the sodium perrhenate precursor is evenly dispersed on the surface of the substrate, which is conducive to the uniform growth of rhenium disulfide;

[0028] 3. In the present invention, the precursor sulfur undergoes melting and recrystallization before the reaction, so that the surface area of ​​the sulfur precursor is determined during the reaction, and the volatilization amount of the sulfur precursor can be effectively controlled;

[0029] 4. The present invention moves the quartz tube of the dual-temperature zone tubular furnace away from the precursor and the substrate, and moves the furnace body to the center of the low-temperature zone and the high-temperature zone after preheating to the set temperature, thereby effectively reducing the reaction time and the temperature variable during the reaction process; after the reaction is completed, the quartz tube of the dual-temperature zone tubular furnace is moved away from the precursor and the substrate, and the inert gas flow is adjusted to 200 sccm at the same time, so as to quickly reduce the temperature of the spatial confinement reaction chamber and quickly terminate the reaction, thereby effectively reducing the generation of by-products;

[0030] 5. The present invention is applicable to a variety of target substrates, including a-plane sapphire, c-plane sapphire, strontium titanate (001), and magnesium oxide (001), and has a certain degree of universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of a method for preparing a single-layer single-crystal rhenium disulfide in an embodiment of the present invention;

[0032] Figure 2 This is a physical picture of the spatially confined reaction chamber in an embodiment of the present invention;

[0033] Figure 3 Schematic diagram of the dual-temperature zone tubular furnace and its quartz tube structure used in the embodiment of the present invention;

[0034] Figure 4 It is a physical picture of the dual-temperature zone tubular furnace and its quartz tube structure used in the embodiment of the present invention;

[0035] Figure 5 is a two-dimensional ReS2 scanning electron microscope image in an embodiment of the present invention;

[0036] Figure 6 is an atomic force microscope image and size statistics diagram of two-dimensional ReS2 in an embodiment of the present invention;

[0037] Figure 7 is a scanning transmission electron microscope image and a selected area electron diffraction pattern of two-dimensional ReS2 in an embodiment of the present invention;

[0038] Figure 8 is an optical microscope image of two-dimensional ReS2 prepared at different reaction temperatures in an embodiment of the present invention;

[0039] Fig. 9 It is an optical microscope image of two-dimensional ReS2 prepared at different sodium perrhenate solution concentrations in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0042] Example:

[0043] Prepare a 10 mm × 10 mm × 0.5 mm single-sided polished c-plane sapphire as a spin coating substrate and a 5 mm × 5 mm × 0.5 mm single-sided polished magnesium oxide (001) as a target substrate;

[0044] Place the spin-coated substrate in an oxygen plasma treatment device, set the power to 50W; start the device, and expose the substrate to the oxygen plasma for 50s; the treated spin-coated substrate will serve as a substrate for loading the Re source precursor;

[0045] Prepare 0.005 mol / L sodium perrhenate solution; place the spin-coated substrate on the spin coater, turn on the vacuum mechanical pump connected to the spin coater, and fix the substrate on the spin coater by negative pressure; set the spin coating parameters, spin coating at a speed of 500 rpm for 10 seconds, and then spin coating at a speed of 3000 rpm for 30 seconds; use a pipette to draw 30 μL of sodium perrhenate solution and drop it on the center of the spin-coated substrate, run the spin coater, and spin coat according to the above-set parameters; after the spin coating is completed, turn off the vacuum mechanical pump and remove the spin-coated substrate;

[0046] The target substrate and the spin-coated substrate loaded with sodium perrhenate are placed opposite to each other with the polished surfaces being the target substrate on top and the spin-coated substrate on the bottom, so as to form a spatially confined reaction chamber.

[0047] S2: Use an analytical balance to weigh 150 mg of sulfur powder and put it into a corundum crucible with a diameter of 10 mm and a height of 5 mm, and place the corundum crucible containing sulfur powder on a hot stage; set the hot stage temperature to 140°C, and remove the corundum crucible containing liquid sulfur from the hot stage after the sulfur powder is completely melted into liquid. After the corundum crucible containing liquid sulfur is cooled to room temperature, the liquid sulfur re-solidifies and crystallizes;

[0048] A corundum crucible loaded with recrystallized sulfur is used as a sulfur source; the gas inlet end of a quartz tube with a diameter of 1 inch is set as the upstream end, and the position overlapping with the insulation ring of the tube furnace is marked as 0 cm. The sulfur source is placed at 16.5 cm marked on the quartz tube, and the spatial confinement reaction chamber is placed on the frosted surface of a 20 mm × 15 mm × 0.5 mm single-sided polished c-plane sapphire, and the whole is placed at 39.5 cm marked on the quartz tube;

[0049] The inlet and outlet flanges were installed at both ends of the quartz tube and ensured to be sealed. Argon gas was introduced at a flow rate of 200 sccm for 10 minutes to expel as much air as possible from the quartz tube.

[0050] S3: When setting the reaction parameters, push the tube furnace away from the reaction area under the condition of argon flow rate of 200sccm. The low temperature zone is set to 150℃, the heating rate is 10℃ / min; the high temperature zone is set to 840℃, and the heating rate is 20℃ / s. At the beginning of the reaction, when the high and low temperature zones reach the target temperature, the argon flow rate is reduced to 40sccm, and the tube furnace is pushed back to the reaction area, so that the sulfur source and the spatial confined reaction chamber are aligned with the center of the low temperature zone and the high temperature zone respectively, and the low temperature zone is maintained at 150℃, the high temperature zone is 840℃, the argon flow rate is 40sccm, and the reaction is carried out for 20 minutes.

[0051] S4: After the reaction is completed, the argon flow rate is adjusted to 200 sccm, and the tube furnace is pushed away from the reaction area after 30 seconds to stop heating the high and low temperature zones. After the tube furnace and the spatial confinement reaction chamber are cooled to room temperature, the argon flow is turned off, the spatial confinement reaction chamber is removed, and a single layer of ReS2 grains is obtained on the surface of the target substrate.

[0052] The scanning electron microscope image and Raman spectrum results of this example are shown in the attached Figure 5 As shown in Figs. a and 5d, the grains are spindle-shaped, and the Raman spectrum shows that the prepared sample is ReS2. The atomic force microscope image and size statistics of the grains in this embodiment are shown in the attached figure. Figure 6 As shown in a and 6b, the grain thickness is 0.9nm and the average size is about 18μm. Scanning transmission electron microscope image ( Figure 7 a) shows that there is no grain boundary within the grains, and the electron diffraction pattern ( Figure 7 b) The diffraction spots have no splitting, indicating that the grains are single crystals, indicating that the ReS2 grains prepared in Example 1 are single crystals.

[0053] The only difference between Examples 2 to 4 and Example 1 is that the spin coating substrate is different, wherein the spin coating substrate in Example 2 is a-plane sapphire, in Example 3 is c-plane sapphire, and in Example 4 is strontium titanate (001).

[0054] Examples 5 to 15 are compared with Example 1, using different growth temperatures and sodium perrhenate solution concentrations, and the other implementation processes are the same as Example 1.

[0055] Table 1 Main parameters for preparing ReS2 in the embodiment

[0056]

[0057]

[0058] In Table 1, serial numbers 1 to 15 represent embodiments 1 to 15 respectively. The effects of embodiments 1 to 4 are as shown in the attached Figure 5 As shown, Examples 5 to 15 are as shown in the attached Figure 8 and attached Fig. 9 shown.

[0059] The method for preparing ReS2 provided by the present invention is applicable to a-plane sapphire, c-plane sapphire, strontium titanate (001) and magnesium oxide (001) and has certain universality, see Examples 1 to 4 (Appendix Figure 5 ).

[0060] By controlling the variable method, controlling the reaction temperature and precursor concentration can affect the product size, thickness and nucleation density. When the low temperature zone is low and the high temperature zone is appropriate, the nucleation density is low, the thickness is thinner, and the size is larger ( Figure 8 a); As the temperature in the low temperature zone rises, the sulfur concentration increases, the nucleation density increases, thick cores begin to appear in the center of the grains, and the size becomes smaller ( Figure 8 bd). When the temperature in the low temperature zone is appropriate and the temperature in the high temperature zone is low, the nucleation density is low, the thickness is thinner, and the size is smaller ( Figure 8 e); As the temperature in the high temperature zone rises, the nucleation density does not change significantly, the size increases first and then decreases, and thick cores begin to appear in the center of the grain ( Figure 8 fh). When the temperatures in the low temperature zone and the high temperature zone are both appropriate and the concentration of the sodium perrhenate solution is low, the nucleation density is low, the thickness is thinner, and the size is smaller ( Fig. 9 a); As the concentration of sodium perrhenate solution increases, the nucleation density increases, the size increases, and thick cores begin to appear in the center of the grains ( Fig. 9 b, c). The test results show that when the temperature in the low temperature zone is 150-170°C, the high temperature zone is 820-850°C, and the concentration of the sodium perrhenate solution is 0.005-0.01 mol / L, the product size, thickness and nucleation density can achieve a good balance.

[0061] The above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition, characterized in that: The method comprises the following steps: S1. Substrate preparation: prepare a spin coating substrate and a target substrate, spin-coat a sodium perrhenate solution on the spin coating substrate, place the target substrate on the spin coating substrate, and place the polished surface of the spin coating substrate and the polished surface of the target substrate face to face to form a slit, thereby forming a spatially confined reaction chamber; S2. Precursor pretreatment and loading: sulfur powder is placed in a corundum crucible for melting and recrystallization as a sulfur source; the sulfur source is placed on one end of the quartz tube of the double-temperature zone tubular furnace close to the air inlet, the spatial confinement reaction chamber is placed on one end of the quartz tube of the double-temperature zone tubular furnace close to the air outlet, the flanges of the air inlet and air outlet are sealed, and then a predetermined flow of inert gas is introduced to completely replace the air in the quartz tube; S3, control reaction: inert gas is introduced into the quartz tube of the double temperature zone tubular furnace, and the center temperature of the high temperature zone of the double temperature zone tubular furnace quartz tube and the center temperature of the low temperature zone of the double temperature zone tubular furnace quartz tube are heated to the set temperature respectively, and then the relative position of the quartz tube and the furnace body is adjusted to make the spatial confined reaction chamber and the sulfur source container react for 15 to 30 minutes; S4. End sampling: After the reaction is completed, adjust the flow rate of the inert gas, cool the quartz tube of the double-temperature zone tubular furnace, and after the quartz tube of the double-temperature zone tubular furnace is cooled to room temperature, take out the spatially confined reaction chamber to obtain a single layer of ReS2 on the surface of the target substrate.

2. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: The spin coating substrate is c-plane sapphire, and the material of the target substrate is c-plane sapphire or a-plane sapphire or strontium titanate or magnesium oxide; The spin-coated substrate is subjected to oxygen plasma treatment for 50 seconds before spin-coating the sodium perrhenate solution, the power is set to 50W, and the concentration of the sodium perrhenate solution is 0.0025-0.05 mol / L; In step S1, when magnesium oxide is used as the target substrate, the single-layer ReS2 grains obtained in S4 are single crystals.

3. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: The method of spin coating the sodium perrhenate solution on the spin coating substrate is to place the spin coating substrate on a spin coating machine, use a pipette to absorb the sodium perrhenate solution and drip it on the surface of the spin coating substrate; the rotation speed of the spin coating machine is 500-5000rpm, and the spin coating time is 30-50s.

4. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 3, characterized in that: The amount of sodium perrhenate solution added during spin coating is 20-50 μL / cm 2 .

5. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: In step S2, sulfur powder is put into a corundum crucible for melting, and heated to 120° C. to 140° C. using a hot plate to melt the sulfur powder, and then cooled to room temperature for recrystallization to obtain a sulfur source; The predetermined flow rate of the inert gas is 40 to 80 sccm, the introduction time is 15 to 30 minutes, and the inert gas is argon or nitrogen.

6. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: The setting temperature of the center temperature of the high temperature zone of the quartz tube of the double-temperature zone tubular furnace is 800-880°C, and the heating rate is 20-40°C / min; the setting temperature of the center temperature of the low temperature zone of the quartz tube of the double-temperature zone tubular furnace is 140-180°C, and the heating rate is 10-20°C / min.

7. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: In step S3, after the central temperature of the high temperature zone and the central temperature of the low temperature zone of the quartz tube of the dual temperature zone tubular furnace reach the set temperature, the spatially confined reaction chamber is aligned with the center of the high temperature zone of the quartz tube of the dual temperature zone tubular furnace, and the sulfur source container is aligned with the center of the low temperature zone of the quartz tube of the dual temperature zone tubular furnace.

8. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 5, characterized in that: In step S4 , the flow rate of the inert gas is adjusted to 200 sccm.

9. The method for preparing a single-layer single-crystal rhenium disulfide by chemical vapor deposition as claimed in claim 1, characterized in that: The single-layer grain size of the ReS2 is 7 to 20 μm.

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