Preparation method of bismuth-oxygen-sulfur two-dimensional material

Abstract

The invention discloses a preparation method of a bismuth-oxygen-sulfur two-dimensional material, which comprises the following steps: S1, preparing a precursor: carrying out first heating on Bi2S3 in a protective gas atmosphere to partially decompose the Bi2S3 to obtain the precursor; the precursor is prepared from Bi and Bi2S3; and S2, confinement growth: placing the precursor between two parallel substrates, clamping the substrates, carrying out second heating in an oxygen-containing atmosphere at the same time, carrying out an oxidation reaction on the precursor, and carrying out adsorption nucleation and growth on an oxidation product on the surfaces of the substrates to form the bismuth-oxygen-sulfur two-dimensional material. According to the preparation method, the low-melting-point precursor is obtained by pretreating Bi2S3, so that the preparation of the bismuth-oxygen-sulfur two-dimensional material at low temperature becomes possible, and the energy consumption is effectively reduced; and the bismuth-oxygen-sulfur two-dimensional material is obtained through a confinement growth method, and the obtained bismuth-oxygen-sulfur two-dimensional material has the characteristics of uniform thickness, controllable size, high yield and high quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic materials, and in particular relates to a method for preparing a bismuth oxygen sulfur two-dimensional material. Background Art

[0002] Due to their ultra-thin thickness, tunable band structure, ultra-large specific surface area and rich physical and chemical properties, two-dimensional materials have been widely used and studied in the fields of infrared photodetectors, solar cells, light-emitting diodes, etc. Despite extensive research on two-dimensional materials, existing low-dimensional material systems still cannot simultaneously meet the requirements of suitable band gap, ultra-high mobility and excellent environmental stability. Therefore, exploring new material systems with high performance remains a challenge.

[0003] As a thermoelectric material, bismuth-based oxychalcogenides (Bi2O2X, X = S, Se, Te) have excellent properties such as good air stability, tunable band structure and high carrier mobility, which have attracted widespread attention from researchers at home and abroad. Through research and development in recent years, the two-dimensional material Bi2O2Se has become an alternative material for van der Waals two-dimensional materials for high-performance electronic and optoelectronic applications, which means that other materials in Bi2O2X also have great development potential, and bismuth oxysulfur (Bi2O2S) may be the next member of such applications.

[0004] Compared with Bi2O2Se, Bi2O2S has the possibility of low-temperature synthesis, has an orthorhombic space structure with a space group of Pnnm, a band gap of 1.5eV, and has the advantages of efficient charge dissociation, high charge carrier transport properties and long carrier lifetime. The stacking structure of Bi2O2S itself can be predicted to have ferroelectricity and ferroelasticity. Therefore, Bi2O2S provides a unique combination of semiconductor properties and ferroelectric / ferroelastic properties for the next generation of electronic and optoelectronic devices.

[0005] However, the lateral dimensions of the two-dimensional Bi2O2S materials reported so far are relatively small. Therefore, the controllable growth of large-area, high-quality two-dimensional Bi2O2S materials is of great significance for further advancing the research and application of Bi2O2S two-dimensional materials. The most commonly used method for growing high-quality two-dimensional materials is chemical vapor deposition (CVD), but so far, there has been no report on the use of CVD to grow two-dimensional Bi2O2S; currently, the mainstream methods for synthesizing Bi2O2S nanostructures are: hydrothermal method or chemical bath deposition method, but the lenses obtained by this method have irregular shapes and extremely small sizes, even less than microns, which makes it inconvenient to study and apply them; there is also a solution-assisted method, but although this method can obtain a large area of ​​Bi2O2S film, its thickness is uneven and the surface is rough. Therefore, at present, growing large-area and uniformly thick two-dimensional Bi2O2S nanosheets is still a challenging task. Summary of the invention

[0006] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a method for preparing bismuth oxysulfur two-dimensional materials, which can prepare large-sized, high-quality bismuth oxysulfur two-dimensional materials on a variety of substrates.

[0007] The second object of the present invention is to provide a bismuth oxygen sulfur two-dimensional material obtained by the above preparation method.

[0008] The third object of the present invention is to provide an application of the above-mentioned bismuth oxygen sulfur two-dimensional material.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] The first aspect of the present invention provides a method for preparing a bismuth oxygen sulfur two-dimensional material, comprising the following steps:

[0011] S1. Preparing a precursor: first heating Bi2S3 in a protective gas atmosphere to partially decompose it to obtain a precursor; the precursor includes Bi and Bi2S3;

[0012] S2. Confined growth: placing the precursor between two parallel substrates, clamping the substrates, and performing a second heating in an atmosphere containing oxygen. The precursor undergoes an oxidation reaction, and the oxidation product is adsorbed on the surface of the substrate to form nuclei and grow, thereby forming the bismuth oxygen sulfur two-dimensional material.

[0013] The inventive concept of the present invention is: by partially decomposing Bi2S3 to form a precursor including Bi and Bi2S3, the melting point of the precursor is reduced to near the melting point of bismuth element, thereby effectively reducing the temperature for preparing the two-dimensional material; and the precursor is sandwiched between two parallel substrates and pressure is applied to form a tiny reaction space between the interlayers. The confined space thus constructed can control the nucleation growth in the near-surface layer of the substrate, so that bismuth oxysulfur grows laterally to obtain a bismuth oxysulfur two-dimensional material; in addition, the two clamped substrates can control the speed at which oxygen in the air participates in the reaction, thereby achieving the purpose of controlling the growth rate and growth quality. The obtained bismuth oxysulfur two-dimensional material has the characteristics of uniform thickness, controllable size, high yield and high quality.

[0014] Preferably, in step S1, the purity of Bi2S3 is ≥99.9%.

[0015] Preferably, in step S1, the amount of Bi2S3 used is 0.1 to 1 g; more preferably, it is 0.15 to 0.5 g.

[0016] Preferably, in step S1, the protective gas includes at least one of nitrogen, argon or helium; further preferably, the protective gas is selected from argon.

[0017] Preferably, in step S1, the protective gas is continuously introduced; the flow rate of the protective gas is 10 to 150 sccm; more preferably, 50 to 100 sccm.

[0018] Preferably, in step S1, the first heating temperature is 650-700°C; more preferably, 670-690°C.

[0019] The decomposition temperature of Bi2S3 at normal pressure is about 685°C. The first heating is used to partially decompose Bi2S3, and the generated sulfur gas is separated from the solid while the bismuth element remains. The bismuth element is fully mixed with the remaining Bi2S3 at high temperature, thereby lowering the melting point of the precursor to near the melting point of bismuth element (about 271.5°C), making it possible to prepare bismuth oxygen-sulfur two-dimensional materials at low temperatures (relative to CVD), effectively reducing energy consumption.

[0020] Preferably, in step S1, the first heating insulation time is 10 to 40 minutes; more preferably, it is 15 to 30 minutes.

[0021] Preferably, in step S1, the heating rate of the first heating is 10 to 30°C / min; more preferably, 15 to 25°C / min.

[0022] Preferably, in step S1, the gas pressure during the first heating is 10-600 Pa; more preferably, 50-500 Pa.

[0023] Preferably, in step S1, the first heating is performed in a heating device; before the first heating is performed, the heating device is purged with a protective gas to discharge oxygen in the heating device. In some specific embodiments of the present invention, the purging treatment is: first evacuating the heating device to a vacuum with a vacuum pressure lower than 1 Pa, then introducing a protective gas at a flow rate of 800 to 1200 sccm to fill the heating device with the protective gas, and repeating this three times to discharge the residual oxygen in the protective gas.

[0024] In some specific embodiments of the present invention, in step S1, the heating device is a tube furnace.

[0025] Preferably, in step S2, the material of the substrate includes fluorphlogopite, <100> Crystalline strontium titanate wafer or <100> At least one of the crystal orientations of single crystal silicon wafers.

[0026] The growth of bismuth oxysulfide on fluorophlogopite is van der Waals epitaxy, which relies on the charge on the surface of fluorophlogopite for growth; while the growth on two substrates, strontium titanate wafers and single crystal silicon wafers, is lattice epitaxy, which requires a very small lattice mismatch, so a specific crystal orientation is needed to match the lattice size of the two.

[0027] Preferably, in step S2, the substrate is peeled or cleaned before the precursor is placed, and the peeled surface or cleaned surface is used as the growth surface of the bismuth oxygen sulfur two-dimensional material.

[0028] Since the substrate surface may be adsorbed with impurities such as water, oxygen, and dust, or there may be a passivation layer on the surface after long-term storage, the size of the two-dimensional material may be affected. The passivation layer may even cause excessive lattice mismatch and make it impossible to grow the two-dimensional material.

[0029] In some specific embodiments of the present invention, in step S2, when the substrate is fluorphlogopite, the fluorphlogopite substrate needs to be peeled off and the freshly dissociated surface is used as the growth surface; <100> When the crystal is strontium titanate wafer, the growth surface is plasma cleaned before use; the substrate is <100> When using a single crystal silicon wafer, soak it in a 0.5-2wt% HF aqueous solution for 5-20 seconds before use to remove the oxide layer on the surface.

[0030] Preferably, in step S2, the pressure applied to clamp the substrate is ≥1 MPa; more preferably, 1-10 MPa.

[0031] In some specific embodiments of the present invention, in step S2, the atmosphere containing oxygen is air.

[0032] Preferably, in step S2, the second heating temperature is 280-500°C; more preferably, 300-400°C.

[0033] Preferably, in step S2, the second heating insulation time is 0.5 to 5 minutes; more preferably, it is 1 to 3 minutes.

[0034] Preferably, in step S2, before placing the precursor between two parallel substrates, the substrate is heated to the second heating temperature. After placing the precursor, the precursor melts, forming the molten precursor into a layer, and then the substrate is clamped to perform subsequent steps. In some specific embodiments of the present invention, the molten precursor is formed into a layer by scraping it flat with a scraper.

[0035] Preferably, the thickness of the layer formed by the molten precursor is ≤0.2 mm; more preferably, it is 0.01 to 0.2 mm.

[0036] Preferably, after the precursor is melted, the time for the molten precursor to form a layer is ≤ 10 s.

[0037] Preferably, in step S2, a post-treatment step is further included after adsorption nucleation and growth, and the post-treatment step includes immersion and / or ultrasound.

[0038] Preferably, the solution used for soaking is a H2O2 aqueous solution; further preferably, the H2O2 aqueous solution is 5 to 15 wt%.

[0039] Preferably, the soaking time is 30 to 100 hours; more preferably, it is 48 to 72 hours.

[0040] Preferably, the ultrasound is performed in water.

[0041] Preferably, the power of the ultrasound is 300-500W; more preferably, it is 350-450W.

[0042] Preferably, the ultrasonic time is 30 to 300 s; more preferably, it is 60 to 120 s.

[0043] The second aspect of the present invention provides a bismuth oxygen sulfur two-dimensional material prepared by the preparation method described in the first aspect of the present invention.

[0044] In some specific embodiments of the present invention, the thickness of the bismuth oxygen sulfur two-dimensional material is 10 to 200 nm; in some more specific embodiments of the present invention, the thickness of the bismuth oxygen sulfur two-dimensional material is 15 to 100 nm.

[0045] In some specific embodiments of the present invention, the area of ​​the bismuth oxygen sulfur two-dimensional material is ≥10 μm 2 In some more specific embodiments of the present invention, the area of ​​the bismuth oxygen sulfur two-dimensional material is 10 to 10 4 μm 2 ; Non-limiting specific example such as 16μm 2 , 25μm 2 , 100μm 2 , 2500μm 2 , 10000μm 2 , 40000μm 2 wait.

[0046] The third aspect of the present invention provides an application of the bismuth oxygen sulfur two-dimensional material described in the second aspect of the present invention in the preparation of optoelectronic devices.

[0047] In some specific embodiments of the present invention, the optoelectronic device includes at least one of an infrared photodetector, a solar cell or a light emitting diode.

[0048] The beneficial effects of the present invention are as follows: the present invention obtains a low-melting-point precursor by pretreating Bi2S3, making it possible to prepare bismuth oxysulfur two-dimensional materials at low temperatures, effectively reducing energy consumption; and obtains bismuth oxysulfur two-dimensional materials by a confined growth method, and the obtained bismuth oxysulfur two-dimensional materials have the characteristics of uniform thickness, controllable size, high yield and high quality.

[0049] Specifically, compared with the prior art, the present invention has the following advantages:

[0050] 1. The preparation method provided by the present invention is green and energy-saving. The material growth process is carried out at a relatively low temperature and can be carried out in the air and utilizes the oxygen in the air, avoiding the high temperature and toxic solvents required by the traditional method. The preparation method provided by the present invention is suitable for large-scale production.

[0051] 2. The preparation method provided by the present invention is easy to operate and has high controllability. It can well solve the problems encountered in the preparation of bismuth oxysulfur two-dimensional materials by traditional methods. The obtained material has the advantages of easy regulation, large chip area, and controllable thickness. It is also beneficial to improve the yield and quality of bismuth oxysulfur two-dimensional materials, and lays a solid foundation for the device integration based on bismuth oxysulfur two-dimensional materials. The bismuth oxysulfur two-dimensional material provided by the present invention has good application prospects in the preparation of optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the preparation process of Bi2O2S two-dimensional material in Example 1.

[0053] Figure 2 These are the optical microscopic images and atomic force microscopy images of the Bi2O2S two-dimensional material of Example 1.

[0054] Figure 3 These are the scanning microscope image, energy spectrometer scanning image and Raman single spectrum image of the Bi2O2S two-dimensional material of Example 1.

[0055] Figure 4 This is the electron diffraction pattern of the Bi2O2S two-dimensional material of Example 1 and the spherical aberration transmission electron microscope image of the material cross section.

[0056] Figure 5 Optical microscopic images of the Bi2O2S two-dimensional materials of Examples 1 to 3.

[0057] Figure 6 These are the optical microscopy images and atomic force microscopy images of the Bi2O2S two-dimensional material of Example 4.

[0058] Figure 7 These are the optical microscopy images and atomic force microscopy images of the Bi2O2S two-dimensional material of Example 5.

[0059] Figure 8 This is an optical microscopic image of the Bi2O2S two-dimensional material of Example 6. DETAILED DESCRIPTION

[0060] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0061] Example 1

[0062] A method for preparing Bi2O2S two-dimensional material, realizing confined growth of large-sized two-dimensional layered material Bi2O2S on fluorophlogopite. The schematic diagram of the preparation process is shown in Figure 1 As shown, (a) is a schematic diagram of the precursor preparation process; (b) is a schematic diagram of the confined growth process, 1 is a heating table, 2 is a substrate, 3 is a molten precursor, 4 is a metal scraper, and 5 is a vise. The specific steps are as follows:

[0063] S1. Raw material selection: Bi2S3 powder with a purity of 99.99% is used as the raw material.

[0064] S2. Substrate selection: A fluorophlogopite mica substrate with a size of 1×1 cm and a thickness of 0.2 mm is used as the substrate.

[0065] S3. Preparation of precursor: Use a balance to weigh 0.2g of Bi2S3 powder and pile it in the heat source center of the tubular furnace. First, evacuate the vacuum of the quartz tube of the tubular furnace to less than 1Pa, and then introduce Ar gas at a flow rate of 1000sccm to fill the quartz tube. Repeat three times to expel the residual oxygen in the quartz tube; heat the tubular furnace to 680℃ at a heating rate of 20℃ / min at a pressure of less than 1Pa, and keep the temperature in the quartz tube at a pressure of 50Pa and an argon flow rate of 50sccm for 30 minutes; after the insulation is completed, it naturally drops to room temperature and take out the gray-black spherical precursor with a metallic luster.

[0066] S4. Confined growth process: first raise the temperature of the heating table to 350℃ and keep it warm; use pointed tweezers to repeatedly peel off the fluorophlogopite substrate, and place it with the freshly dissociated surface as the growth surface facing up; cut a small piece of precursor and place it on the fluorophlogopite, the precursor will melt quickly, use a 3×2cm steel scraper to evenly spread the molten precursor on the surface of the fluorophlogopite with a thickness of no more than 0.2mm, and then use another piece of fluorophlogopite with the freshly dissociated surface facing down to cover it; use a steel vise to press the fluorophlogopite and precursor tightly against the surface of the heating table at a pressure of 1.5MPa, keep it for 1min to allow the two-dimensional Bi2O2S nanosheets to grow, and then remove the vise; separate the two pieces of fluorophlogopite and remove the heating table to cool naturally.

[0067] S5. Post-processing process: Soak the fluorphlogopite mica sheet with the grown material in a 10wt% H2O2 aqueous solution for 48 hours to oxidize the precursor that has not participated in the reaction into powder, and ultrasonicate it in a 400W ultrasonic machine for 1 minute to remove powdery impurities, thereby obtaining a clean and flat Bi2O2S two-dimensional material.

[0068] Figure 2 The optical microscopic image and atomic force microscopic image of the Bi2O2S two-dimensional material of Example 1, wherein (a) is an optical microscopic image; (b) is an atomic force microscopic (AFM) image. Figure 2 It can be seen that the Bi2O2S nanosheets grown on the fluorophlogopite mica sheets are square with a side length of about 10 microns, have good uniformity and are only 20nm thick.

[0069] Figure 3 The scanning microscope image, energy spectrometer scanning image and Raman spectrum image of the Bi2O2S two-dimensional material of Example 1, wherein (a) is a scanning microscope (SEM) image and an energy spectrometer scanning image (EDS mapping) of the three elements Bi, O, and S; (b) is a Raman spectrum image. Figure 3 It can be seen that the Bi, O, and S elements of the Bi2O2S nanosheets are evenly distributed; the Raman peak of the Bi2O2S nanosheets is obvious and consistent with the unique vibration peak of Bi2O2S, which proves that the prepared Bi2O2S nanosheets have good uniformity and high crystal quality.

[0070] Figure 4 The electron diffraction pattern of the Bi2O2S two-dimensional material of Example 1 and the spherical aberration transmission electron microscope image of the material cross section, wherein (a) is the electron diffraction pattern; (b) is the spherical aberration transmission electron microscope image of the material cross section. Figure 4 It can be seen that the Bi2O2S nanosheets have a regular structure under transmission electron microscopy and spherical aberration transmission electron microscopy, and are consistent with the theoretically calculated Bi2O2S structure, indicating that the Bi2O2S nanosheets prepared in this example have excellent crystal quality.

[0071] Example 2

[0072] A method for preparing a Bi2O2S two-dimensional material. The difference between this embodiment and embodiment 1 is that in step S4, the growth temperature in the confined growth process is adjusted to 300°C, and the other steps and control parameters are the same as in embodiment 1.

[0073] Example 3

[0074] A method for preparing a Bi2O2S two-dimensional material. The difference between this embodiment and embodiment 1 is that in step S4, the growth temperature in the confined growth process is adjusted to 400°C, and the other steps and control parameters are the same as in embodiment 1.

[0075] Figure 5 The optical microscopic images of the Bi2O2S two-dimensional materials of Examples 1 to 3, wherein (a) is Example 2; (b) is Example 1; and (c) is Example 3. Figure 5 It can be seen that by controlling the growth temperature during the confined growth process, the size and thickness of the Bi2O2S two-dimensional material can be controlled. Within the temperature range of 300-400°C, the higher the growth temperature during the confined growth process, the larger the size and the thicker the grown Bi2O2S two-dimensional material, which reflects the controllability of the method of the present invention.

[0076] Example 4

[0077] A method for preparing Bi2O2S two-dimensional material, <100> The confined growth of large-scale two-dimensional layered material Bi2O2S was achieved on a crystal-oriented strontium titanate wafer. The specific steps are as follows:

[0078] S1. Raw material selection: Bi2S3 powder with a purity of 99.99% is used as the raw material.

[0079] S2. Substrate selection: size 5×5mm, thickness 0.5mm <100> Crystalline strontium titanate wafers were used as substrates.

[0080] S3. Preparation of precursor: Use a balance to weigh 0.2g of Bi2S3 powder and pile it in the heat source center of the tubular furnace. First, evacuate the vacuum of the quartz tube of the tubular furnace to less than 1Pa, and then introduce Ar gas at a flow rate of 1000sccm to fill the quartz tube. Repeat three times to expel the residual oxygen in the quartz tube; heat the tubular furnace to 680℃ at a heating rate of 20℃ / min at a pressure of less than 1Pa, and keep the temperature in the quartz tube at a pressure of 50Pa and an argon flow rate of 50sccm for 30 minutes; after the insulation is completed, it naturally drops to room temperature and take out the gray-black spherical precursor with a metallic luster.

[0081] S4. Confined growth process: first raise the temperature of the heating table to 325°C and keep it warm; put the strontium titanate substrate into a plasma cleaner, use argon gas to clean it for 15 minutes, then take it out and place it with the cleaned surface facing up as the growth surface; cut a small piece of precursor and put it on the strontium titanate wafer. The precursor will melt quickly. Use a 3×2cm steel scraper to evenly spread the molten precursor on the surface of the strontium titanate wafer with a thickness of no more than 0.2mm, and then use another strontium titanate substrate with a clean surface to cover it downward; use a steel vise to press the strontium titanate substrate and the precursor tightly against the surface of the heating table at a pressure of 1MPa. Keep it for 1min to allow the two-dimensional Bi2O2S nanosheets to grow, and then remove the vise; separate the two strontium titanate substrates and remove them from the heating table to cool naturally.

[0082] S5. Post-treatment process: The strontium titanate substrate with the grown material is immersed in a 5wt% H2O2 aqueous solution for 48 hours to oxidize the precursor that has not participated in the reaction into powder, and ultrasonicate it in a 400W ultrasonic machine for 30 seconds to remove powdery impurities, thereby obtaining a clean and flat Bi2O2S two-dimensional material.

[0083] Figure 6 The optical microscopic image and atomic force microscopic image of the Bi2O2S two-dimensional material of Example 4, wherein (a) is an optical microscopic image; (b) is an atomic force microscopic (AFM) image. Figure 6 It can be seen that in <100> The Bi2O2S nanosheets grown on the strontium titanate wafer are square in shape, with a side length of about 4 microns, good uniformity and a thickness of only about 12 nm. <100> The growth method on the strontium titanate wafer is lattice epitaxy.

[0084] Example 5

[0085] A method for preparing Bi2O2S two-dimensional material, <100> The confined growth of large-scale two-dimensional layered material Bi2O2S is achieved on a single-crystal silicon wafer. The specific steps are as follows:

[0086] S1. Raw material selection: Bi2S3 powder with a purity of 99.99% is used as the raw material.

[0087] S2. Substrate selection: size 1×1cm, thickness 0.5mm <100> The crystal-oriented single-crystalline silicon wafer is used as the substrate.

[0088] S3. Preparation of precursor: Use a balance to weigh 0.2g of Bi2S3 powder and pile it in the heat source center of the tubular furnace. First, evacuate the vacuum of the quartz tube of the tubular furnace to less than 1Pa, and then introduce Ar gas at a flow rate of 1000sccm to fill the quartz tube. Repeat three times to expel the residual oxygen in the quartz tube; heat the tubular furnace to 680℃ at a heating rate of 20℃ / min at a pressure of less than 1Pa, and keep the temperature in the quartz tube at a pressure of 50Pa and an argon flow rate of 50sccm for 30 minutes; after the insulation is completed, it naturally drops to room temperature and take out the gray-black spherical precursor with a metallic luster.

[0089] S4, confined growth process: first raise the temperature of the heating table to 350℃ and keep it warm; immerse the single crystal silicon wafer in a 1wt% HF aqueous solution for 10s to remove the oxide layer on the surface, and place the cleaned surface with the growth surface facing up; cut a small piece of precursor and place it on the single crystal silicon wafer, the precursor will melt quickly, use a 3×2cm steel scraper to evenly spread the molten precursor on the surface of the single crystal silicon wafer with a thickness not exceeding 0.2mm, and then use the clean surface of another single crystal silicon wafer to cover it downward; use a steel vise to press the single crystal silicon wafer and the precursor tightly against the surface of the heating table at a pressure of 1.5MPa, keep it for 2min to allow the two-dimensional Bi2O2S nanosheets to grow, and then remove the vise; separate the two single crystal silicon wafers and remove the heating table to cool naturally.

[0090] S5. Post-processing process: Soak the single crystal silicon wafer with the grown material in a 10wt% H2O2 aqueous solution for 72 hours to oxidize the precursor that has not participated in the reaction into powder, and ultrasonicate it in a 400W ultrasonic machine for 90 seconds to remove powder impurities, thereby obtaining a clean and flat Bi2O2S two-dimensional material.

[0091] Figure 7 The optical microscopic image and atomic force microscopic image of the Bi2O2S two-dimensional material of Example 5, wherein (a) is an optical microscopic image; (b) is an atomic force microscopic (AFM) image. Figure 7 It can be seen that <100> The Bi2O2S nanosheets grown on the single crystal silicon wafer are square, with a side length of about 5 microns, good uniformity and a thickness of about 75nm. <100> The growth method on the crystal-oriented single-crystalline silicon wafer is lattice epitaxy.

[0092] Example 6

[0093] A method for preparing a Bi2O2S two-dimensional material. The difference between this embodiment and embodiment 4 is that the growth temperature in the confined growth process is adjusted to 400°C, and the vise pressure is adjusted to 2MPa. The other steps and control parameters are the same as those in embodiment 4.

[0094] Figure 8This is an optical microscopic image of the Bi2O2S two-dimensional material of Example 6. Figure 8 It can be seen that by adjusting the temperature and pressure of confined growth, the area of ​​the obtained Bi2O2S two-dimensional material can be adjusted. Under the conditions of Example 6, a large-area two-dimensional Bi2O2S nanofilm can be obtained, and the area of ​​the region exceeds 200μm×200μm.

[0095] The embodiment of the present invention uses two substrates to sandwich the molten precursor in the middle, and uses a clamp to apply a certain pressure to form a tiny reaction space between the layers. The confined space thus constructed controls the nucleation growth in the near-surface layer, and Bi2O2S grows laterally to obtain two-dimensional Bi2O2S nanosheets; by regulating parameters such as precursor composition, growth time, growth temperature, and growth pressure, high-quality large-size two-dimensional layered material Bi2O2S is finally obtained.

[0096] The preparation method provided by the embodiment of the present invention is green and energy-saving. The material growth process is carried out at a relatively low temperature and can be carried out in the air and utilizes the oxygen in the air, avoiding the high temperature and toxic solvents required by the traditional method. The preparation method provided by the present invention is suitable for large-scale production. In addition, the preparation method provided by the embodiment of the present invention is easy to operate and highly controllable, and can well solve the problems that arise in the preparation of bismuth oxygen sulfur two-dimensional materials by traditional methods. The obtained material has the advantages of easy regulation, large chip area, and controllable thickness. At the same time, it is conducive to improving the yield and quality of bismuth oxygen sulfur two-dimensional materials, and lays a solid foundation for the device integration based on bismuth oxygen sulfur two-dimensional materials. The bismuth oxygen sulfur two-dimensional materials provided by the present invention have good application prospects in the preparation of optoelectronic devices.

[0097] In summary, the present invention obtains a low-melting-point precursor by pretreating Bi2S3, making it possible to prepare bismuth oxysulfur two-dimensional materials at low temperatures, effectively reducing energy consumption; and obtains bismuth oxysulfur two-dimensional materials by a confined growth method, and the obtained bismuth oxysulfur two-dimensional materials have the characteristics of uniform thickness, controllable size, high yield and high quality.

Claims

1. A method for preparing bismuth oxygen sulfur two-dimensional material, characterized in that: The following steps are involved: S1. Preparing a precursor: first heating Bi2S3 in a protective gas atmosphere to partially decompose it to obtain a precursor; the precursor includes Bi and Bi2S3; S2. Confined growth: placing the precursor between two parallel substrates, clamping the substrates, and performing a second heating in an atmosphere containing oxygen. The precursor undergoes an oxidation reaction, and the oxidation product is adsorbed on the surface of the substrate to form nuclei and grow, thereby forming the bismuth oxygen sulfur two-dimensional material.

2. The preparation method according to claim 1, characterized in that: In step S1, the purity of Bi2S3 is ≥99.9%; And / or, in step S1, the amount of Bi2S3 used is 0.1 to 1 g.

3. The preparation method according to claim 1, characterized in that: In step S1, the first heating temperature is 650-700°C; And / or, in step S1, the first heating holding time is 10 to 40 minutes; And / or, in step S1, the heating rate of the first heating is 10 to 30°C / min; And / or, in step S1, the gas pressure during the first heating is 10-600 Pa.

4. The preparation method according to claim 1, characterized in that: In step S2, the material of the substrate includes fluorphlogopite, <100> Crystalline strontium titanate wafer or <100> At least one of the crystal orientations of single crystal silicon wafers.

5. The preparation method according to claim 1, characterized in that: In step S2, the pressure applied to clamp the substrate is ≥1 MPa.

6. The preparation method according to claim 1, characterized in that: In step S2, the second heating temperature is 280-500°C; And / or, in step S2, the second heating insulation time is 0.5 to 5 minutes.

7. The preparation method according to claim 1, characterized in that: In step S2, after adsorption nucleation and growth, a post-treatment step is also included, and the post-treatment step includes soaking and / or ultrasound; Preferably, the solution used for the soaking is a H2O2 aqueous solution; and / or the soaking time is 30 to 100 hours; and / or the ultrasonic power is 300 to 500 W; and / or the ultrasonic power is 30 to 300 s.

8. A bismuth oxygen sulfur two-dimensional material obtained by the preparation method as described in any one of claims 1 to 7.

9. The bismuth oxygen sulfur two-dimensional material according to claim 8, characterized in that The thickness of the bismuth oxygen sulfur two-dimensional material is 10 to 200 nm; And / or, the area of ​​the bismuth oxygen sulfur two-dimensional material is ≥ 10 μm 2 .

10. Use of the bismuth oxygen sulfur two-dimensional material as claimed in claim 8 or 9 in the preparation of optoelectronic devices.

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