CN114477105A

CN114477105A - Two-dimensional BiCuSeO nanosheet, preparation method thereof and semiconductor device

Info

Publication number: CN114477105A
Application number: CN202210321021.8A
Authority: CN
Inventors: 张凯; 李�杰; 张严; 张君蓉; 汪永杰; 俞强
Original assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Current assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2022-05-13
Anticipated expiration: 2042-03-30
Also published as: CN114477105B

Abstract

The invention discloses a two-dimensional BiCuSeO nanosheet, a preparation method thereof and a semiconductor device, wherein the preparation method comprises the following steps: providing a reaction device, wherein the reaction device comprises a low-pressure reaction chamber, and the reaction chamber is provided with a first area and a second area which are sequentially arranged at intervals; placing a selenium-containing precursor in a first area, and placing a copper-containing precursor and an oxygen-containing precursor in a second area; the growth substrate is placed in the two areas and is reversely buckled above the copper-containing precursor and the oxygen-containing precursor; and (4) performing heat treatment, namely evaporating and reacting the selenium-containing precursor, the copper-containing precursor and the oxygen-containing precursor, and obtaining the BiCuSeO nano sheet on the surface of the growth substrate. The invention realizes the preparation of the two-dimensional BiCuOSe nanosheet with the minimum thickness of 7.6nm and the maximum transverse dimension of 270 mu m by a Chemical Vapor Deposition (CVD) method.

Description

Two-dimensional BiCuSeO nanosheet, preparation method thereof and semiconductor device

Technical Field

The invention relates to the technical field of semiconductor materials, in particular to a two-dimensional BiCuSeO nanosheet, a preparation method thereof and a semiconductor device.

Background

Due to the rapidly evolving demands of microelectronics, the size of conventional silicon-based transistors is continuously shrinking following moore's law. As transistors shrink to their physical limits, a series of problems develop, such as the power consumption of the devices increasing significantly. In order to reduce the power consumption of a CMOS transistor, it is effective to reduce the applied voltage when the transistor is turned from an off state to an on state. The minimum value of this applied voltage is determined by the size of the thermal ion barrier across the source when carriers are injected into the channel. Thus, for a conventional transistor, the minimum value of the sub-threshold swing (SS) at room temperature is 60mV/dec, i.e., the Boltzmann limit. Due to the presence of the boltzmann limit, the power consumption of the integrated circuit is greatly increased, reducing the performance (on-current and on-off ratio) of the transistor. To make the SS of the transistor less than 60mV/dec, two common approaches are to utilize a heterojunction-based tunneling transistor (T-FET) and a ferroelectric gate-based negative capacitance transistor (NC-FET). Different from the common MOSFET which crosses a potential barrier to form current by means of carrier thermal injection, the tunneling transistor for realizing carrier transportation based on band-band tunneling is not limited by the Boltzmann limit, and has the advantages of low subthreshold swing and high on-off ratio. For a T-FET, the realization of a tunneling effect needs to regulate and control a Fermi level through a grid voltage, and a traditional semiconductor transistor has an obvious Fermi pinning effect due to factors such as doping, interface defects and the like, so that the regulation and control of the grid voltage on the concentration of carriers are limited. Therefore, it is difficult to realize a conventional semiconductor transistor having an SS value lower than 60mV/dec and a high on-off ratio at room temperature. Compared with the traditional semiconductor material, the two-dimensional material has the unique advantages of thickness of atomic level, natural dangling bond-free interface, ultrahigh mobility, no influence of lattice mismatch on stacking and the like. In recent years, a tunneling transistor with low power consumption and high switching ratio based on a two-dimensional material 2D-2D heterojunction and a 3D-2D composite structure is gradually a hot spot of research.

So far, there are many reports based on various two-dimensional material heterojunction tunneling transistors. However, for a 2D-2D tunneling transistor formed by constructing a heterojunction in a two-dimensional material, although the SS value can be reduced to some extent, it is still difficult to break through the boltzmann limit at room temperature. And there are two possible reasons for this.

First, there is a shortage of p-type two-dimensional material. So far, the majority of the carrier types of common two-dimensional materials are electrons, the p-type two-dimensional materials are rarely selected, and the p-type two-dimensional materials commonly used for experimental research comprise Black Phosphorus (BP), black arsenic phosphorus (b-AsP), tellurium (Te), gallium selenide (GaSe) and some bipolar two-dimensional materials WSe₂、MoTe₂And so on, to a limited extent. Moreover, most of the materials are unstable in air (such as BP), which brings great limitation to the establishment of heterojunction by energy band matching to realize tunneling.

Second, the two-dimensional material itself is generally low in carrier concentration and difficult to dope. The two-dimensional material of the atomic layer thickness makes it difficult to carry out a controllable optimization of the carrier concentration and type by modulation doping as in conventional semiconductors. Controllable doping of two-dimensional materials has been one of the limiting factors for their widespread use. Although the two-dimensional material can be adjusted to some extent by applying a gate voltage, the carrier concentration of the two-dimensional material itself is low (less than 10)¹⁸cm^-3) It is difficult to realize heavy doping by gate voltage regulation. And due to the limitation of the carrier concentration, a high electric field is difficult to form between the channel and the source and the drain of the tunneling heterojunction, and the probability of carrier tunneling into the channel is reduced.

By combining the factors, the p-type two-dimensional material with intrinsic heavy doping is searched, and the method is very important for constructing a 2D-2D heterojunction tunneling transistor and realizing the preparation of a tunneling transistor device with low SS and high on-off ratio. BiCuSeO is a thermoelectric material with excellent performance, and the appropriate energy band gap (0.4-0.9 eV), intrinsic p-type heavy doping and stable chemical properties provide possibility for the construction of a 2D-2D heterojunction tunneling transistor. So far, BiCuSeO can mostly prepare single crystal blocks only by a solid-phase reaction method and a fluxing agent method. However, due to the electrostatic force existing between atomic layers of BiCuSeO itself, it is difficult to obtain a nanosheet with a single atomic layer or several atomic layers by mechanical exfoliation like graphene. Although BiCuSeO can obtain nanosheets with thicknesses of only a few atomic layers through a solution method, the nanosheets are small in lateral size (smaller than 1 μm), random and irregular in shape, and cannot meet the requirements of a semiconductor device preparation process.

Disclosure of Invention

The invention aims to provide a two-dimensional BiCuSeO nanosheet, a preparation method thereof and a semiconductor device, which can solve the problems of small transverse size and random and irregular shape in the prior art.

In order to achieve the above object, an embodiment of the present invention further provides a preparation method of a two-dimensional BiCuSeO nanosheet, including:

providing a reaction device, wherein the reaction device comprises a low-pressure reaction chamber, and the reaction chamber is provided with a first area and a second area which are sequentially arranged at intervals;

placing a selenium-containing precursor in a first area, placing a copper-containing precursor, an oxygen-containing precursor and a growth substrate in a second area, and inversely covering the growth substrate above the copper-containing precursor and the oxygen-containing precursor;

and (4) performing heat treatment, namely evaporating and reacting the selenium-containing precursor, the copper-containing precursor and the oxygen-containing precursor, and obtaining the BiCuSeO nano sheet on the surface of the growth substrate.

In one or more embodiments of the present invention, the selenium-containing precursor is selected from one or more of bismuth selenide, copper selenide, elemental selenium powder, or elemental selenium bulk; the oxygen-containing precursor is selected from one or more of bismuth oxide and copper oxide; the copper-containing precursor is selected from one or more of copper oxide, copper selenide, elemental copper powder and elemental copper foil.

In one or more embodiments of the present invention, the selenium-containing precursor is bismuth selenide, the copper-containing precursor is copper powder, and the oxygen-containing precursor is bismuth oxide.

In one or more embodiments of the invention, the mass ratio of copper, bismuth selenide and bismuth oxide is 1 (10-50) to (50-100).

In one or more embodiments of the present invention, the present invention further includes a flux disposed in the second region, wherein the flux is one or more of potassium chloride, sodium chloride, and copper chloride.

In one or more embodiments of the invention, the distance between the first and second regions is from 5cm to 15 cm.

In one or more embodiments of the present invention, the heat treatment comprises: heating to 600-720 ℃ within 20-30 min, and keeping the temperature for 5-30 min.

In one or more embodiments of the invention, the vaporized precursor is delivered to the growth substrate during the heat treatment by continuously flowing 50-150sccm of inert gas.

In order to achieve the above object, an embodiment of the present invention further provides a two-dimensional BiCuSeO nanosheet, which is prepared by the preparation method, and the thickness of the nanosheet is 7.6nm to 100 nm; the lateral dimension is 5 μm to 270 μm.

In order to achieve the above object, an embodiment of the present invention further provides a semiconductor device, including the two-dimensional BiCuSeO nanosheet.

Compared with the prior art, the preparation method disclosed by the invention realizes the preparation of the two-dimensional BiCuOSe nanosheet with the minimum thickness of 7.6nm and the maximum transverse dimension of 270 mu m by a simple Chemical Vapor Deposition (CVD) method. And the characteristic of intrinsic p-type heavy doping is verified. The method has important significance for the preparation and research of semiconductor devices in the future.

Drawings

FIG. 1 is a schematic view of a reaction apparatus according to an embodiment of the present invention;

fig. 2a and b show an optical microscope image of a two-dimensional BiCuSeO nanosheet and its corresponding Atomic Force Microscope (AFM) image provided in embodiment 1 of the present invention, fig. 2c and d show an optical microscope image of a two-dimensional BiCuSeO nanosheet and its corresponding Atomic Force Microscope (AFM) image provided in embodiment 2 of the present invention, and fig. 2e and f show an optical microscope image of a two-dimensional BiCuSeO nanosheet and its corresponding Atomic Force Microscope (AFM) image provided in embodiment 3 of the present invention;

fig. 3 is a Scanning Electron Microscope (SEM) image of a two-dimensional bicusseo nanosheet provided in example 1 of the present invention;

fig. 4 is a view of a spherical aberration electron microscope (STEM) atomic image and element distribution scan (mapping) of a two-dimensional BiCuSeO nanosheet provided in embodiment 1 of the present invention, where a is a low-power high-angle annular dark field image of the BiCuSeO nanosheet, b is a high-power high-angle annular dark field image, and c-f are distribution scan views of Bi, Cu, Se, and O elements in the BiCuSeO nanosheet, respectively;

FIG. 5 is an elemental analysis chart of a two-dimensional BiCuSeO nanosheet in example 1 of the present invention;

fig. 6 shows an X-ray diffraction (XRD) pattern of a two-dimensional BiCuSeO nanosheet provided in example 3 of the present invention;

fig. 7 a shows a test chart of lateral resistance of a two-dimensional bicuiseo nanosheet hall device provided in embodiment 1 of the present invention changing with a magnetic field, fig. 7b shows a test chart of resistance of a corresponding hall device changing with a changing temperature, and fig. 7 c shows a fourier infrared spectroscopy (FTIR) test chart of the two-dimensional bicuiseo nanosheet provided in embodiment 3.

Detailed Description

The solid-phase reaction method is the most common method for preparing BiCuSeO (copper bismuth selenide oxide) at present, but the reaction period is long, the obtained product is impure and easy to generate impurities, only a block material with uncontrollable appearance can be synthesized, and a two-dimensional BiCuSeO nano sheet cannot be obtained. The flux method can obtain pure-phase BiCuSeO bulk materials, but cannot obtain two-dimensional nanosheets with the thickness of less than 100 nm. The BiCuSeO nanosheet can be obtained by a solution method, but the transverse size of the BiCuSeO nanosheet is very small (less than 1 mu m), and the shape of the obtained nanosheet is not controllable, so that the BiCuSeO nanosheet cannot be used for preparation and related research of semiconductor devices.

In order to solve the technical problem, the invention provides a preparation method of a two-dimensional BiCuSeO nanosheet, which comprises the steps of placing a growth substrate and a precursor in a quartz tube by a Chemical Vapor Deposition (CVD) growth method, and vacuumizing to synthesize the growth substrate and the precursor under a low-pressure condition. The low-melting-point selenium source is placed at the upstream of the tube furnace, the high-melting-point copper source and the oxygen source are placed at the center of the tube furnace, the mica substrate is reversely buckled on the high-melting-point source, and inert gas is introduced to convey the precursor. And then heating the tube furnace to a certain temperature, preserving the temperature, evaporating the precursor, reacting to generate BiCuSeO, and depositing, nucleating and epitaxially growing on a growth substrate to form a two-dimensional BiCuSeO nanosheet. The preparation method provided by the embodiment of the invention has the advantages of low raw material price, low production equipment cost, simplicity and safety in operation, high controllability and strong repeatability, and the obtained BiCuSeO nanosheets are uniform and controllable in thickness, are suitable for large-area production of two-dimensional BiCuSeO, and meet research requirements and industrialization requirements in practical application.

The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.

A two-dimensional BiCuSeO nanosheet according to a preferred embodiment of the present invention, having a thickness of from 7.6nm to 100nm, preferably from 7.6nm to 50 nm; the lateral dimension is 5 μm to 270 μm.

In the technical scheme, the thickness of the two-dimensional nanosheet is less than 100nm, the transverse size of the two-dimensional nanosheet is greater than 5 microns, the two-dimensional nanosheet can be used for preparing a semiconductor device, and particularly, the preparation method is very important for constructing a 2D-2D heterojunction (heterojunction formed by stacking two-dimensional materials) tunneling transistor and realizing the preparation of a low SS (sub-threshold swing) and high on-off ratio tunneling transistor device.

The embodiment of the invention also provides a preparation method of the two-dimensional BiCuSeO nanosheet, which comprises the following steps:

referring to fig. 1, a reaction apparatus 100 is provided, where the reaction apparatus 100 includes a low-pressure reaction chamber 11, and the reaction chamber 11 has a first region 111 and a second region 112 arranged at intervals in sequence;

placing a selenium-containing precursor 12 in a first region 111, placing a copper-containing precursor and an oxygen-containing precursor 13, and placing a growth substrate 14 in a second region 112, wherein the growth substrate 14 is inverted over the copper-containing precursor and the oxygen-containing precursor 13;

and (4) performing heat treatment, namely evaporating and reacting the selenium-containing precursor 12, the copper-containing precursor and the oxygen-containing precursor 13, and obtaining the BiCuSeO nano sheet on the surface of the growth substrate 14.

In the embodiment, the two-dimensional BiCuSeO single crystal nanosheet with controllable thickness and size is successfully prepared by a simple Chemical Vapor Deposition (CVD) method, and the method can be widely applied to the related fields of thermoelectricity, semiconductor devices and the like. Compared with the prior art, the chemical vapor deposition method has the advantages of simple operation, safe raw materials, simple equipment, low cost, good repeatability, high crystallinity, high quality, smooth surface, uniform thickness and the like.

In an actual manufacturing process, the "low-pressure reaction chamber" may be an inner cavity of a quartz tube for heating reaction, which is directly placed in a heating cavity of a heating device, such as a tube furnace.

It should be noted that the vacuum-tight reaction chamber includes, but is not limited to, the above-described implementation manner, and may be any growth apparatus or growth container of a vacuum-tight reaction chamber capable of implementing the two-dimensional BiCuSeO nanosheet growth.

In some embodiments, the selenium-containing precursor includes, but is not limited to, one or more of bismuth selenide, copper selenide, and the like, or even elemental selenium powder (bulk), which can be thermally decomposed to produce selenium.

In some embodiments, the oxygen-containing precursor includes, but is not limited to, one or more of bismuth oxide, copper oxide, and the like, which can be thermally decomposed to generate oxygen.

In some embodiments, the copper-containing precursor includes, but is not limited to, copper oxide, copper selenide, and one or more of the compounds that can decompose to form copper upon heating, and even elemental copper powder (foil).

In some embodiments, the growth substrate may include, but is not limited to, a silicon dioxide sheet, a fluorophlogopite sheet, a quartz sheet, a sapphire sheet, and the like.

In a specific embodiment, the selenium-containing precursor is bismuth selenide, the copper-containing precursor is copper powder, and the oxygen-containing precursor is bismuth oxide. In the embodiment, the mass ratio of the copper to the bismuth selenide to the bismuth oxide is 1 (10-50) to 50-100.

In some embodiments, the flux is disposed in the second region, and the flux includes, but is not limited to, any one or more of low melting point chlorides such as potassium chloride, sodium chloride, copper chloride, and the like.

In some embodiments, the distance between the first region and the second region is 5cm to 15 cm. The temperature difference between the first zone and the second zone is in the range of 50-200 ℃. When the distance is too small, the selenium source temperature is high, the evaporation amount is large, and other products such as Cu are easily generated₂And (5) Se. The temperature of the selenium source is low and the evaporation capacity is too small when the distance is too far, so that BiCuSeO cannot be generated due to insufficient selenium source.

The second area is located in a temperature area with higher temperature in the vacuum-tight reaction chamber, and the first area is located in a temperature area with lower temperature in the vacuum-tight reaction chamber. The temperature in the direction from the second region to the first region will vary in a gradient, i.e. the temperature in the second region > the temperature in the first region.

In some embodiments, the heat treating comprises: heating to 600-720 ℃ within 20-30 min, and keeping the temperature for 5-30 min.

In some embodiments, the vaporized precursor is delivered to the growth substrate during the thermal treatment by continuously flowing 50-150sccm of an inert gas. Transport inert gases include, but are not limited to, argon, nitrogen, and the like.

The embodiment of the invention also provides a semiconductor device which comprises the two-dimensional BiCuSeO nanosheet or the two-dimensional BiCuSeO nanosheet prepared by the method. In one embodiment, the semiconductor device may be a transistor.

Example 1

Selecting a plurality of pieces of clean mica as growth substrates for later use. Selecting bismuth selenide (Bi)₂Se₃) As a selenium source, bismuth oxide (Bi)₂O₃) As an oxygen source, copper oxide (CuO) was used as a copper source, and potassium chloride (KCl) was used as a flux. The mass ratio of the copper oxide to the bismuth selenide to the bismuth oxide is 1:20: 80.

The low melting point bismuth selenide is placed at the upstream of the tube furnace (10 cm away from the center), the high melting point copper oxide, bismuth oxide and potassium chloride are placed at the center of the tube furnace, and the mica substrate is reversely buckled on the high melting point source. The vacuum pump is opened to vacuumize to below 1Pa, and 100-200sccm argon is repeatedly introduced to perform gas washing to remove the oxygen in the quartz tube.

And (3) raising the temperature of the tubular furnace to 660 ℃ within 25min, keeping the temperature for 10min after raising the maximum temperature, and naturally cooling to room temperature. During the whole process of temperature rise, heat preservation and cooling, 100sccm argon is continuously introduced as transport and protective gas.

The two-dimensional BiCuSeO nanosheet obtained in the embodiment is shown in FIG. 2a, the nanosheet is rectangular, and the maximum transverse dimension can reach 84 μm; FIG. 2b shows the corresponding AFM characterization, which is 7.6nm thick.

Fig. 3 is an SEM representation of the two-dimensional BiCuSeO nanosheet obtained in this example, and it can be seen that the surface thereof is uniform and has no significant secondary nucleation.

Fig. 4 and fig. 5 are spherical aberration electron microscope representations of the two-dimensional bicusseo nanosheets obtained in this example, which illustrate the high quality and high crystallinity (no obvious defect) of the two-dimensional nanosheets, and the two-dimensional nanosheets contain Bi, Cu, Se and O and are uniformly distributed.

The two-dimensional BiCuSeO nanosheet obtained by the implementation case is large in transverse size, thin and uniform in thickness, and free of obvious secondary nucleation on the surface, and a material foundation is laid for the preparation of the Hall device. Therefore, the hall device test based on this embodiment is as shown in fig. 7 a, b: in fig. 7, a illustrates that the carrier type of the two-dimensional BiCuSeO nanosheet obtained by the present invention is a hole; in fig. 7, b indicates that the resistance of the BiCuSeO nanosheet increases with increasing temperature, and becomes metallic.

Example 2

Selecting a plurality of pieces of clean mica as growth substrates for later use. Selecting bismuth selenide (Bi)₂Se₃) As a selenium source, bismuth oxide (Bi)₂O₃) As an oxygen source, copper powder (Cu) was used as a copper source, and potassium chloride (KCl) was used as a flux. The mass ratio of the copper powder to the bismuth selenide to the bismuth oxide is 1:50: 100.

The low-melting point bismuth selenide is placed at the upstream of the tube furnace (15 cm away from the center), the high-melting point copper powder, bismuth oxide and potassium chloride are placed at the center of the tube furnace, the mica substrate is reversely buckled on the high-melting point source, and 100-stream and 200-sccm argon gas is repeatedly introduced for gas scrubbing to remove oxygen in the quartz tube.

And (3) heating the tube furnace to 700 ℃ within 25min, keeping the temperature for 30min after the temperature is raised to the maximum temperature, and naturally cooling to room temperature. During the whole process of temperature rise, heat preservation and cooling, 100sccm argon is continuously introduced as transport and protective gas.

The two-dimensional BiCuSeO nanosheet obtained in this embodiment is shown in fig. 2 c. Due to the higher temperature of the embodiment, the nano-sheet with the transverse dimension of 277 mu m can be obtained. Meanwhile, the excessively evaporated precursor is further reacted and deposited on the nano-sheet, so that obvious secondary nucleation and growth exist on the nano-sheet, and the edge of the nano-sheet has a phenomenon of laminated growth. Figure 2d is a corresponding AFM characterization, illustrating that the thickness of the nanoplatelets is 17.4 nm.

Example 3

Selecting a plurality of pieces of clean mica as growth substrates for later use. Selecting bismuth selenide (Bi)₂Se₃) As a selenium source, bismuth oxide (Bi)₂O₃) As an oxygen source, copper powder (Cu) was used as a copper source, and potassium chloride (KCl) was used as a flux. The mass ratio of the copper powder to the bismuth selenide to the bismuth oxide is 1:10: 50.

The low melting point bismuth selenide is placed at the upstream of the tube furnace (5 cm away from the center), the high melting point copper, bismuth oxide and potassium chloride are placed at the center of the tube furnace, and the mica substrate is reversely buckled on the high melting point source. The vacuum pump is opened to vacuumize to below 1Pa, and 100-200sccm argon is repeatedly introduced to perform gas washing to remove the oxygen in the quartz tube.

And (3) heating the tubular furnace to 620 ℃ within 25min, keeping the temperature for 10min after the temperature is raised to the highest temperature, and naturally cooling to room temperature. During the whole process of temperature rise, heat preservation and cooling, 100sccm argon is continuously introduced as transport and protective gas.

The two-dimensional BiCuSeO nanosheet obtained in the embodiment and AFM characterization thereof are shown in FIGS. 2e and 2 f. The relative content of the copper source is higher, so that the nucleation density is increased; the growth temperature of the system is low, the transverse transportation of the precursor on the substrate is limited, and only a sample with high nucleation density, transverse size smaller than 20 mu m and thickness larger than 50nm can be obtained. High density nucleation growth provides conditions for testing XRD and FTIR: as shown in fig. 6, the two-dimensional BiCuSeO nanosheet obtained in this example is illustrated, and its exposed crystal plane is the (100) crystal plane family; as shown in c in fig. 7, FTIR test gave a band gap of 0.45eV for BiCuSeO nanosheets. The two-dimensional BiCuSeO nanosheet synthesized by the invention is illustrated as a p-type heavily doped semiconductor by combining the test results of the Hall devices a and 7b in FIG. 7 of example 1.

In summary, the embodiment of the invention successfully prepares the two-dimensional BiCuSeO single crystal nanosheet with controllable thickness and size by a simple Chemical Vapor Deposition (CVD) method, and the two-dimensional BiCuSeO single crystal nanosheet can be widely applied to the related fields of thermoelectricity, semiconductor devices and the like. The chemical vapor deposition method has the advantages of simple operation, safe raw materials, simple equipment, low cost and good repeatability, and the prepared nanosheet has the advantages of high crystallinity, high quality, smooth surface, uniform thickness and the like.

The foregoing description of specific exemplary embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims

1. A preparation method of a two-dimensional BiCuSeO nanosheet is characterized by comprising the following steps:

2. The method for preparing a two-dimensional BiCuSeO nanosheet of claim 1, wherein the selenium-containing precursor is selected from one or more of bismuth selenide, copper selenide, elemental selenium powder, or elemental selenium mass;

the oxygen-containing precursor is selected from one or more of bismuth oxide and copper oxide;

the copper-containing precursor is selected from one or more of copper oxide, copper selenide, elemental copper powder and elemental copper foil.

3. The method of making two-dimensional BiCuSeO nanosheets of claim 2, wherein the selenium-containing precursor is bismuth selenide, the copper-containing precursor is copper powder, and the oxygen-containing precursor is bismuth oxide.

4. The method for preparing two-dimensional BiCuSeO nanosheets of claim 3, wherein the mass ratio of copper to bismuth selenide to bismuth oxide is 1 (10-50) to (50-100).

5. A method of making two-dimensional BiCuSeO nanoplates as defined in claim 1, further comprising a fluxing agent disposed in said second region,

the fluxing agent is one or more of potassium chloride, sodium chloride and copper chloride.

6. A method of making two-dimensional BiCuSeO nanoplates as in claim 1, wherein the distance between the first and second regions is 5cm-15 cm.

7. A method of making two-dimensional BiCuSeO nanoplates as in claim 1, wherein the thermal treatment comprises: heating to 600-720 ℃ within 20-30 min, and keeping the temperature for 5-30 min.

8. The method for preparing two-dimensional BiCuSeO nanosheets as claimed in claim 1, wherein during the heat treatment, an inert gas of 50-150sccm is continuously introduced and the evaporated precursor is delivered to the growth substrate.

9. A two-dimensional BiCuSeO nanoplate, produced by the method of any one of claims 1 to 8, having a thickness of from 7.6nm to 100nm and a lateral dimension of from 5 μ ι η to 270 μ ι η.

10. A semiconductor device comprising the two-dimensional BiCuSeO nanosheet of claim 9.