A two-dimensional Bi4Se3 single crystal with superlattice structure and preparation method thereof

Abstract

The present invention relates to a two-dimensional Bi4Se3 single crystal with a superlattice structure and a preparation method thereof. The two-dimensional Bi4Se3 single crystal with a superlattice structure is a monolayer single crystal nanosheet in the shape of a regular hexagon, with an equivalent diameter of 5-20 μm and a thickness of 4-25 nm. The two-dimensional Bi4Se3 single crystal with a superlattice structure provided by the present invention is a large-sized single crystal with controllable thickness, and can be as thin as a single layer at the lowest. It has certain application prospects as an optoelectronic material under the two-dimensional layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal growth, and in particular relates to a two-dimensional Bi4Se3 single crystal with a superlattice structure and a preparation method thereof. Background Art

[0002] (Bi2) m (Bi2Se3) n It is a very important homologous series of compounds. Through the different stacking sequences of Bi-Bi zigzag double electric layer and Se-Bi-Se-Bi-Se-Se five electric layers, various layered heterostructure compounds are formed under the action of van der Waals interlayer. Bi4Se3 as (Bi2 m (Bi2Se3) n An important member of the family, it has been identified as a topological quantum material, and band contact occurs at the Fermi level, where two or more bands are exactly degenerate at a specific crystal momentum value in the first Brillouin zone, and is a potential candidate for catalysis, photovoltaics, thermomagnetic transport, and spin electronics. Bi4Se3 synthesized by high-temperature solid phase shows ultra-low lattice thermal conductivity and high n-type thermoelectric performance close to room temperature. However, the materials synthesized by high-temperature solid phase are usually polycrystalline powders, and it is impossible to advance the preparation of Bi4Se3 to the two-dimensional level. In particular, the preparation method of two-dimensional Bi4Se3 single crystal nanosheets with a single layer thickness has not been reported. This is mainly because as a layered superlattice structure compound, the atomic diffusion ability through the interlayer van der Waals gap is very low, and it is extremely difficult to accurately insert the Bi layer into the interlayer to achieve the growth of the superlattice structure. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a two-dimensional Bi4Se3 single crystal with a superlattice structure and a preparation method thereof in view of the above-mentioned deficiencies in the prior art. A chemical vapor deposition preparation method in which a substrate induces the two-dimensional van der Waals epitaxial growth of Bi4Se3 is adopted to obtain for the first time a single-layer two-dimensional Bi4Se3 single crystal nanosheet with a size exceeding 10 μm and a superlattice structure.

[0004] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0005] Provided is a two-dimensional Bi4Se3 single crystal with a superlattice structure, which is a single-layer single crystal nanosheet in a regular hexagonal shape, with an equivalent diameter of 5 to 20 μm and a thickness of 4 to 25 nm.

[0006] The present invention also provides a method for preparing the above-mentioned two-dimensional Bi4Se3 single crystal with a superlattice structure: using a mica substrate as a substrate, Bi2O3 powder and Bi2Se3 powder as precursors, and argon as a carrier gas, a chemical vapor deposition method is adopted to prepare a two-dimensional Bi4Se3 single crystal with a superlattice structure on the surface of the mica substrate, and then the two-dimensional Bi4Se3 single crystal is peeled off from the mica substrate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

[0007] According to the above scheme, the specific steps of the preparation method are as follows:

[0008] 1) Using a chemical vapor deposition device with two heating zones, the two heat source zones are 14 to 18 cm apart, placing a mica substrate in the downstream heating zone, placing Bi2O3 powder and Bi2Se3 powder in different porcelain boats, and then placing the porcelain boat containing Bi2O3 powder in the upstream heating zone of the chemical vapor deposition device, and placing the porcelain boat containing Bi2Se3 powder upstream of the Bi2O3 powder;

[0009] 2) evacuating the chemical vapor deposition equipment, then introducing argon gas, and then heating to perform chemical vapor deposition to prepare a two-dimensional Bi4Se3 single crystal with a superlattice structure on the surface of a mica substrate;

[0010] 3) Evenly spin-coating a polymethyl methacrylate solution on one side of the mica substrate on which the two-dimensional Bi4Se3 single crystal is grown, heating to solidify the polymethyl methacrylate, then peeling off the polymethyl methacrylate on the surface of the mica substrate together with the two-dimensional Bi4Se3 single crystal wrapped therein, and finally using a solvent to dissolve and remove the polymethyl methacrylate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

[0011] According to the above scheme, in step 1), the purity of the Bi2O3 powder is above 99.999wt%, the purity of the Bi2Se3 powder is above 99.999wt%, and the mass ratio of the Bi2O3 powder to the Bi2Se3 powder is 1.5 to 5:1.

[0012] According to the above scheme, in step 1), the porcelain boat containing Bi2O3 powder is 4 to 8 cm away from the porcelain boat containing Bi2Se3 powder.

[0013] According to the above scheme, the mica substrate in step 1) is peeled off before use to make the surface flat and clean, and then ultrasonically cleaned with ethanol, acetone and deionized water in sequence, and blown dry with nitrogen.

[0014] According to the above scheme, in step 2), the purity of argon gas is above 99.99 vol%, and the flow rate of argon gas is 100-200 sccm.

[0015] According to the above scheme, the chemical vapor deposition process conditions in step 2) are: the deposition gas pressure is 200-400 Torr, the upstream heat source zone is heated to 750-850°C at a heating rate of 10-15°C / min at room temperature, and the downstream heat source zone is heated to 700-800°C at a heating rate of 8-13°C / min, so that the two heat source zones reach the target temperature at the same time, and then kept warm for 5-20 minutes.

[0016] According to the above scheme, the polymethyl methacrylate solution in step 3) is obtained by dissolving polymethyl methacrylate in anisole, and the concentration is 0.1-0.3 g / mL.

[0017] According to the above scheme, the solvent in step 3) is acetone.

[0018] The present invention also includes the application of the above-mentioned two-dimensional Bi4Se3 single crystal with superlattice structure in the field of optoelectronic materials.

[0019] The present invention breaks through the limitation that the Bi4Se3 preparation process under the existing preparation process cannot control the precise insertion of Bi atoms, and can only prepare polycrystalline powder, which makes it difficult to prepare two-dimensional Bi4Se3 single crystals. A mica substrate with the same van der Waals layered structure is selected as the substrate to induce interlayer insertion and two-dimensional growth, and the gas flow rate, deposition pressure, nucleation time, growth time and other parameters are comprehensively controlled to achieve the preparation of superlattice structure two-dimensional Bi4Se3 single crystals.

[0020] The beneficial effects of the present invention are as follows: 1. The two-dimensional Bi4Se3 single crystal with a superlattice structure provided by the present invention is a large-size single crystal with controllable thickness, which can be as low as a single layer, and has certain application prospects as a two-dimensional optoelectronic material. 2. The preparation method of the present invention is easy to operate and has high repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a chemical vapor deposition apparatus used in Example 1 of the present invention;

[0022] Figure 2 This is an optical micrograph of the superlattice structure two-dimensional Bi4Se3 single crystal prepared in Example 1;

[0023] Figure 3 The Raman spectrum of the two-dimensional Bi4Se3 single crystal prepared in Example 1;

[0024] Figure 4 An atomic force microscope image of the two-dimensional Bi4Se3 single crystal prepared in Example 1;

[0025] Figure 5 TEM high resolution of the two-dimensional Bi4Se3 single crystal prepared in Example 1;

[0026] Figure 6 This is the lattice diffraction pattern of the two-dimensional Bi4Se3 single crystal prepared in Example 1. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0028] Example 1

[0029] A two-dimensional Bi4Se3 single crystal with a superlattice structure, the preparation method of which is as follows:

[0030] 1) The newly peeled mica substrate was ultrasonically cleaned with ethanol, acetone and deionized water for 10 minutes respectively, dried with nitrogen and placed in the downstream heat source area of ​​the chemical vapor deposition equipment. The schematic diagram of the chemical vapor deposition device is shown in Figure 1 As shown, the upstream and downstream heat source areas are 16 cm apart, 0.4 g Bi2O3 powder (99.999 wt%, purchased from Alfa Aesar) and 0.2 g Bi2Se3 (99.999 wt%, purchased from Alfa Aesar) powder are placed in different porcelain boats, the porcelain boat containing Bi2O3 powder is placed in the upstream heat source area of ​​the chemical vapor deposition equipment, and the porcelain boat containing Bi2Se3 powder is placed 6 cm upstream of the Bi2O3 powder;

[0031] 2) The chemical vapor deposition equipment was evacuated to a pressure below 10Pa, and then argon gas (purity 99.99 vol%) was introduced at a flow rate of 400 sccm for 20 minutes to clean the pipeline. The gas flowed through a porcelain boat containing Bi2Se3 powder, a porcelain boat containing Bi2O3 powder and a mica substrate in turn. Then the argon flow rate was adjusted to 200 sccm, the deposition pressure was controlled to 350 Torr, and the power of the upstream heat source zone and the downstream heat source zone was turned on. The upstream heat source zone was heated to 850°C and the downstream heat source zone was heated to 800°C for 50 minutes, and then kept warm for 20 minutes to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure on the mica substrate;

[0032] 3) After the mica substrate is naturally cooled, it is taken out, and a polymethyl methacrylate (PMMA, purchased from Aladdin, cas number: 9011-14-7) anisole solution (concentration of 0.1 g / mL) is evenly spin-coated on the surface of one side of the mica substrate where the two-dimensional Bi4Se3 single crystal is grown. Then, it is heated at 160°C for 10 min to volatilize the anisole and solidify the polymethyl methacrylate. Then, the polymethyl methacrylate on the surface of the mica substrate together with the two-dimensional Bi4Se3 single crystal wrapped therein is peeled off. Finally, hot acetone is used to dissolve and remove the polymethyl methacrylate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

[0033] Figure 2 This is an optical micrograph of the two-dimensional Bi4Se3 single crystal with a superlattice structure prepared in this embodiment. It can be seen that its morphology is a two-dimensional single crystal in the shape of a regular hexagon, with an equivalent diameter of 5-20 μm.

[0034] Figure 3 This is the Raman spectrum of the two-dimensional Bi4Se3 single crystal prepared in this example. It can be seen from the figure that the -1 , 92.5cm -1 , 111.6cm -1 and 151.2cm -1 The four Raman signal peaks at are the Raman characteristic peaks of Bi4Se3, indicating that Bi4Se3 was successfully prepared.

[0035] Figure 4 The atomic force microscope image of the two-dimensional Bi4Se3 single crystal prepared in this embodiment shows that the thickness of the two-dimensional Bi4Se3 nanosheet is 4nm, which is consistent with the theoretical thickness of a single layer of Bi4Se3, indicating that the prepared superlattice structure two-dimensional Bi4Se3 single crystal is a single layer.

[0036] Figure 5 and Figure 6 They are the TEM high-resolution and lattice diffraction images of the two-dimensional Bi4Se3 single crystal prepared in this embodiment. From the high-resolution lattice spacing, it can be confirmed that it is a two-dimensional Bi4Se3 single crystal. From the lattice diffraction, it can be seen that there are two sets of lattice diffraction patterns, which correspond to the diffraction of Bi2 and Bi2Se3 lattices respectively, which indicates that the sample has a superlattice structure.

[0037] Example 2

[0038] A two-dimensional Bi4Se3 single crystal with a superlattice structure, the preparation method of which is as follows:

[0039] 1) The newly peeled mica substrate was ultrasonically cleaned with ethanol, acetone and deionized water for 10 minutes respectively, dried with nitrogen and placed in the downstream heat source area of ​​the chemical vapor deposition equipment, with the upstream and downstream heat source areas 16 cm apart, 0.3g Bi2O3 powder and 0.1g Bi2Se3 powder were placed in different porcelain boats, the porcelain boat containing Bi2O3 powder was placed in the upstream heat source area of ​​the chemical vapor deposition equipment, and the porcelain boat containing Bi2Se3 powder was placed 6cm upstream of the Bi2O3 powder;

[0040] 2) The chemical vapor deposition equipment was evacuated to a pressure below 10Pa, and then argon gas (purity 99.99 vol%) was introduced at a flow rate of 400 sccm for 20 minutes to clean the pipeline. The gas flowed through a porcelain boat containing Bi2Se3 powder, a porcelain boat containing Bi2O3 powder and a mica substrate in turn. Then the argon flow rate was adjusted to 100 sccm, the deposition pressure was controlled to 400 Torr, and the power of the upstream heat source zone and the downstream heat source zone was turned on. The upstream heat source zone was heated to 800°C for 50 minutes, and the downstream heat source zone was heated to 750°C. Then the temperature was kept at this temperature for 10 minutes to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure on the mica substrate.

[0041] 3) After the mica substrate is naturally cooled, it is taken out, and a polymethyl methacrylate anisole solution (concentration of 0.1 g / mL) is evenly spin-coated on the surface of one side of the mica substrate where the two-dimensional Bi4Se3 single crystal is grown. Then, it is heated at 160°C for 10 min to volatilize the anisole and solidify the polymethyl methacrylate. Then, the polymethyl methacrylate on the surface of the mica substrate together with the two-dimensional Bi4Se3 single crystal wrapped therein is peeled off. Finally, hot acetone is used to dissolve and remove the polymethyl methacrylate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

[0042] Example 3

[0043] A two-dimensional Bi4Se3 single crystal with a superlattice structure, the preparation method of which is as follows:

[0044] 1) The newly peeled mica substrate was ultrasonically cleaned with ethanol, acetone and deionized water for 10 minutes respectively, dried with nitrogen and placed in the downstream heat source area of ​​the chemical vapor deposition equipment, with the upstream and downstream heat source areas 16 cm apart, 0.2g Bi2O3 powder and 0.1g Bi2Se3 powder were placed in different porcelain boats, the porcelain boat containing Bi2O3 powder was placed in the upstream heat source area of ​​the chemical vapor deposition equipment, and the porcelain boat containing Bi2Se3 powder was placed 6 cm upstream of the Bi2O3 powder;

[0045] 2) The chemical vapor deposition equipment was evacuated to a pressure below 10Pa, and then argon gas (purity 99.99 vol%) was introduced at a flow rate of 400 sccm for 20 minutes to clean the pipeline. The gas flowed through a porcelain boat containing Bi2Se3 powder, a porcelain boat containing Bi2O3 powder and a mica substrate in turn. Then the argon flow rate was adjusted to 150 sccm, the deposition pressure was controlled to 200 Torr, and the power of the upstream heat source zone and the downstream heat source zone was turned on. The upstream heat source zone was heated to 750°C and the downstream heat source zone was heated to 700°C for 50 minutes, and then kept warm for 15 minutes to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure on the mica substrate;

[0046] 3) After the mica substrate is naturally cooled, it is taken out, and a polymethyl methacrylate anisole solution (concentration of 0.1 g / mL) is evenly spin-coated on the surface of one side of the mica substrate where the two-dimensional Bi4Se3 single crystal is grown. Then, it is heated at 160°C for 10 min to volatilize the anisole and solidify the polymethyl methacrylate. Then, the polymethyl methacrylate on the surface of the mica substrate together with the two-dimensional Bi4Se3 single crystal wrapped therein is peeled off. Finally, hot acetone is used to dissolve and remove the polymethyl methacrylate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

Claims

1. A two-dimensional Bi4Se3 single crystal with a superlattice structure, characterized in that: It is a single-layer single-crystal nanosheet in the shape of a regular hexagon, with an equivalent diameter of 5 to 20 μm and a thickness of 4 to 25 nm.

2. A method for preparing a two-dimensional Bi4Se3 single crystal having a superlattice structure according to claim 1, characterized in that: A two-dimensional Bi4Se3 single crystal with a superlattice structure is prepared on the surface of a mica substrate by chemical vapor deposition using a mica substrate as a substrate, Bi2O3 powder and Bi2Se3 powder as precursors, and argon as a carrier gas. Then, the two-dimensional Bi4Se3 single crystal is peeled off from the mica substrate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure. The specific steps are as follows: 1) Using a chemical vapor deposition device with two heating zones, the two heat source zones are 14 to 18 cm apart, placing a mica substrate in the downstream heating zone, placing Bi2O3 powder and Bi2Se3 powder in different porcelain boats, and then placing the porcelain boat containing Bi2O3 powder in the upstream heating zone of the chemical vapor deposition device, and placing the porcelain boat containing Bi2Se3 powder upstream of the Bi2O3 powder; 2) The chemical vapor deposition equipment is evacuated, and then argon gas is introduced, the purity of the argon gas is more than 99.99 vol%, the argon gas flow rate is 100-200 sccm, and then the temperature is increased for chemical vapor deposition to prepare a two-dimensional Bi4Se3 single crystal with a superlattice structure on the surface of the mica substrate. The chemical vapor deposition process conditions are: the deposition pressure is 200-400 Torr, the upstream heat source zone is heated to 750-850°C at a heating rate of 10-15°C / min at room temperature, and the downstream heat source zone is heated to 700-800°C at a heating rate of 8-13°C / min, so that the two heat source zones reach the target temperature at the same time, and then the temperature is kept for 5-20 minutes; 3) Evenly spin-coating a polymethyl methacrylate solution on one side of the mica substrate on which the two-dimensional Bi4Se3 single crystal is grown, heating to solidify the polymethyl methacrylate, then peeling off the polymethyl methacrylate on the surface of the mica substrate together with the two-dimensional Bi4Se3 single crystal wrapped therein, and finally using a solvent to dissolve and remove the polymethyl methacrylate to obtain a two-dimensional Bi4Se3 single crystal with a superlattice structure.

3. The method for preparing a two-dimensional Bi4Se3 single crystal having a superlattice structure according to claim 2, characterized in that: Step 1) The purity of the Bi2O3 powder is above 99.999wt%, the purity of the Bi2Se3 powder is above 99.999wt%, and the mass ratio of the Bi2O3 powder to the Bi2Se3 powder is 1.5-5:

1.

4. The method for preparing a two-dimensional Bi4Se3 single crystal having a superlattice structure according to claim 2, characterized in that: Step 1) The porcelain boat containing Bi2O3 powder and the porcelain boat containing Bi2Se3 powder are 4 to 8 cm apart.

5. The method for preparing a two-dimensional Bi4Se3 single crystal having a superlattice structure according to claim 2, characterized in that: Step 3) The polymethyl methacrylate solution is obtained by dissolving polymethyl methacrylate in anisole, and the concentration is 0.1-0.3 g / mL.

6. The method for preparing a two-dimensional Bi4Se3 single crystal having a superlattice structure according to claim 2, characterized in that: Step 3) The solvent is acetone.

7. Application of the two-dimensional Bi4Se3 single crystal with superlattice structure as claimed in claim 1 in the field of optoelectronic materials.

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