阅读说明：本技术 一种大尺寸二维碘化铋单晶的制备方法 (Preparation method of large-size two-dimensional bismuth iodide single crystal ) 是由 张翅腾飞 涂溶 罗国强 郑颖秋 张联盟 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种大尺寸二维碘化铋单晶的制备方法,包括如下步骤：S1,将碘化铋粉末放置到设有一端开口的刚玉舟内,再将氟金云母基板倒扣在刚；S3,往管式炉中通入氩气与氢气,对气化的碘化铋进行稀释并进行还原反应；S4,在反应结束后,将气相陷阱移动至管式炉末端的加热带处进行降温,在降温过程中,使刚玉舟内的气体在氟金云母基板上沉积形成附着；S5,待气相陷阱完全冷却后,获得二维碘化铋单晶。本发明的本发明公开一种大尺寸二维碘化铋单晶的制备方法,解决了现有方法制得的碘化铋单晶尺寸较小且厚度不可控的问题,整体制备工艺简单、操作方便、可重复性好,通过控制降温速率,得到不同厚度和尺寸的二维单晶碘化铋。(The invention discloses a preparation method of a large-size two-dimensional bismuth iodide single crystal, which comprises the following steps: s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on a steel; s3, introducing argon and hydrogen into the tubular furnace, diluting the gasified bismuth iodide, and carrying out reduction reaction; s4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process; and S5, obtaining the two-dimensional bismuth iodide single crystal after the gas-phase trap is completely cooled. The invention discloses a preparation method of a large-size two-dimensional bismuth iodide single crystal, which solves the problems that the bismuth iodide single crystal prepared by the existing method is small in size and uncontrollable in thickness, has a simple integral preparation process, is convenient to operate and good in repeatability, and can be used for obtaining the two-dimensional single-crystal bismuth iodide with different thicknesses and sizes by controlling the cooling rate.)

1. A preparation method of a large-size two-dimensional bismuth iodide single crystal is characterized by comprising the following steps:

s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on the corundum boat to form a gas-phase trap;

s2, placing the gas-phase trap at the central position of the tube furnace, and heating to make the bismuth iodide powder reach the volatilization temperature;

s3, introducing argon and hydrogen into the tube furnace, diluting the gasified bismuth iodide in a constant-temperature environment, and carrying out reduction reaction;

s4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process;

s5, after the gas-phase trap is completely cooled, collecting powder attached to the fluorophlogopite substrate to obtain a two-dimensional bismuth iodide single crystal;

wherein 0.1-1 g of the added bismuth iodide powder is introduced with argon as a diluent gas and hydrogen as a reducing gas, and the two-dimensional bismuth iodide single crystal has a size of 200-1000 mu m and a thickness of 5-500 nm.

2. The method for producing a large-sized two-dimensional bismuth iodide single crystal according to claim 1, wherein: the opening direction of the corundum boat is opposite to the air flow direction of the introduced argon and hydrogen.

3. The method for producing a large-sized two-dimensional bismuth iodide single crystal according to claim 2, wherein: in the step S2, the volatilization temperature is 280-380 ℃.

4. The method for producing a large-sized two-dimensional bismuth iodide single crystal according to claim 3, wherein: in the step S3, the time of the reduction reaction is 5-15 min, the flow of the introduced argon gas is 10-100 sccm, and the flow of the introduced hydrogen gas is 5-50 sccm.

5. The method for producing a large-sized two-dimensional bismuth iodide single crystal according to any one of claims 1 to 4, wherein: the heating zone at the tail end of the tubular furnace is distributed in a gradient mode, and the temperature range is 25-175 ℃.

6. The method for producing a large-sized two-dimensional bismuth iodide single crystal according to claim 5, wherein: the different temperature ranges of the heating band can enable the gas phase trap after the reaction to obtain different cooling rates, and further regulate and control the thickness and the size of the two-dimensional bismuth iodide single crystal.

Technical Field

The invention belongs to the technical field of two-dimensional material preparation, and particularly relates to a preparation method of a large-size two-dimensional bismuth iodide single crystal.

Background

Two-dimensional materials are a general term for a broad class of layered materials that are connected by strong covalent bonds within the layers and weak van der waals forces between layers, and thus, the size and thickness of the two-dimensional material can be adjusted by changing the deposition temperature, pressure or gas flow. Generally, when the thickness of a two-dimensional material is reduced below 10nm, the properties of the material are greatly changed due to the influence of surface effects and size effects. For example: bulk graphite is only a good conductor of electricity, while double-layer graphene is a semiconductor. Nowadays, the research of two-dimensional materials is mainly focused on graphene, boron nitride and nitrogen and oxygen group materials (e.g. Bi)₂Se₃、VTe₂And MoS₂Etc.).

In recent years, studies on two-dimensional halide single crystals have been reported. Among them, a two-dimensional magnetic material represented by chromium iodide and a two-dimensional photoelectric material represented by lead iodide have become a new research hotspot. However, chromium iodide is extremely unstable in air, and lead iodide contains lead elements that are highly toxic to the environment and human body, which hinders their further use. Bismuth iodide is stable in air and has little influence on the environment and human body, and can be widely applied to the fields of optics, semiconductors and the like.

Bismuth iodide is an indirect bandgap semiconductor with an energy gap of 1.5eV, and the basic structure of the semiconductor is an octahedron formed by bismuth and iodine. Bismuth iodide has a large atomic number (Z)_Bi＝83，Z_I53) and density (5.78 g/cm)³) The detector is suitable for being used as a high-performance detector for radiation detection or X-ray detection. It also has great third-order nonlinear polarizability, has strong exciton transmission, and is suitable for the field of nonlinear optics. Besides, bismuth iodide can also be applied to the photovoltaic field, and has higher carrier mobility (260 +/-50 cm)²V.s) and defect insensitive Properties, oftenIs an absorber layer of a solar cell.

The growth of bulk bismuth iodide single crystals is well established and single crystal bismuth iodide with single crystal size over 2cm can be grown using Physical Vapor Transport (PVT) or Bridgman method. However, the growth of two-dimensional bismuth iodide single crystals is still in a nearly blank stage, and the maximum size is still less than 10 μm, so that further application cannot be carried out.

Disclosure of Invention

The invention aims to solve the technical problem of providing a preparation method of a large-size two-dimensional bismuth iodide single crystal, which can form the large-size two-dimensional bismuth iodide single crystal, has controllable thickness and good repeatability.

The technical scheme for solving the technical problems comprises the following steps:

a preparation method of a large-size two-dimensional bismuth iodide single crystal comprises the following steps:

s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on the corundum boat to form a gas-phase trap; the gas-phase trap is formed by reversely buckling the fluorophlogopite substrate on the corundum boat, and the corundum boat is provided with an opening at one end, can capture bismuth iodide steam, and plays a critical role in the growth of two-dimensional bismuth iodide single crystals. In the present invention, only fluorophlogopite substrate can be used as the substrate in the process of preparing the two-dimensional bismuth iodide, if other kinds of substrates (e.g., Al) are used₂O₃Soda lime glass or Si) can only be grown to obtain single crystal bismuth iodide with a size less than 40 μm, mainly because: 1. fluorophlogopite is a material with a layered structure and surface roughness<0.1nm, much smaller than other substrates. 2. The outermost layer of fluorophlogopite is positively charged K⁺Has a promoting effect on the nucleation of the two-dimensional bismuth iodide.

S2, placing the gas-phase trap at the central position of the tube furnace, and heating to make the bismuth iodide powder reach the volatilization temperature;

s3, introducing argon and hydrogen into the tube furnace, diluting the gasified bismuth iodide in a constant-temperature environment, and carrying out reduction reaction;

s4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process;

s5, after the gas-phase trap is completely cooled, collecting powder attached to the fluorophlogopite substrate to obtain a two-dimensional bismuth iodide single crystal; the gas-phase trap is moved to the heating zone, the temperature of the heating zone is mainly used for controlling the cooling rate of the gas-phase trap, different heating zones can enable the cooling of the gas-phase trap to form different rates after the tube furnace is closed, and the main reason is that the cooling time lengths of different heating zones are different, so that the cooling time length of the gas-phase trap can be controlled to a certain extent.

Wherein 0.1-1 g of the added bismuth iodide powder is introduced with argon as a diluent gas and hydrogen as a reducing gas, and the two-dimensional bismuth iodide single crystal has a size of 200-1000 mu m and a thickness of 5-500 nm.

Specifically, the opening direction of the corundum boat is opposite to the gas flow direction of the introduced argon and hydrogen.

Specifically, in the step S2, the volatilization temperature is 280 to 380 ℃.

Specifically, in the step S3, the reduction reaction time is 5 to 15min, the flow of the introduced argon gas is 10 to 100sccm, and the flow of the introduced hydrogen gas is 5 to 50 sccm. When the gas is higher than the upper limit, the etching effect of the hydrogen gas is intensified, and the size of the obtained bismuth iodide is smaller. When the gas is below the upper limit, the bismuth iodide vapor accumulated in the gas phase trap is excessive, resulting in a sharp increase in nucleation density of the grown bismuth iodide.

Preferably, the heating belt at the tail end of the tubular furnace is in gradient distribution, and the temperature range is 25-175 ℃.

Specifically, the different temperature ranges of the heating zone can enable the gas phase trap after the reaction to obtain different cooling rates, so as to regulate and control the thickness and size of the two-dimensional bismuth iodide single crystal. Two-dimensional bismuth iodide single crystals with good crystallinity, large size and controllable thickness can be grown within the preferable growth temperature range. When the growth temperature is higher than the upper temperature limit, the decomposition of the bismuth iodide precursor is severe, so that the grown bismuth iodide single crystal has smaller size and thicker thickness. When the growth temperature is lower than the lower temperature limit, the bismuth iodide precursor is not easy to volatilize, and bismuth iodide cannot grow.

The invention has the following beneficial effects: the method solves the problems that the bismuth iodide single crystal prepared by the existing method is small in size and uncontrollable in thickness, the overall preparation process is simple, convenient to operate and good in repeatability, the bismuth iodide vapor is captured by using a gas-phase trap consisting of a substrate and a corundum boat, the cooling rate of the gas-phase trap is controlled by utilizing heating, the purpose of growing the large-size two-dimensional bismuth iodide single crystal is achieved, and meanwhile, the two-dimensional single crystal bismuth iodide with different thicknesses and sizes can be obtained by controlling the cooling rate.

Drawings

FIG. 1 is a graph showing a temperature decrease rate of a gas phase trap according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings.

Example 1:

the preparation method of the large-size two-dimensional bismuth iodide single crystal in the embodiment 1 of the invention comprises the following steps:

s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on the corundum boat to form a gas-phase trap; wherein the amount of bismuth iodide powder added was 1 g.

S2, placing the gas-phase trap at the central position of the tube furnace, and heating to make the bismuth iodide powder reach the volatilization temperature; specifically, the opening direction of the corundum boat is opposite to the air flow direction of the introduced argon and hydrogen, and the volatilization temperature is 380 ℃.

S3, introducing argon and hydrogen into the tube furnace, diluting the gasified bismuth iodide in a constant-temperature environment, and carrying out reduction reaction; argon gas is introduced as a diluent gas, and hydrogen gas is introduced as a reducing gas. Specifically, the time of the reduction reaction was 15min, the flow rate of introduced argon gas was 10sccm, and the flow rate of introduced hydrogen gas was 5 sccm.

S4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process; preferably, the heating zone at the end of the tube furnace is in gradient distribution, the temperature range is 25-175 ℃, in this embodiment, the gas phase trap is placed at the heating zone with the temperature of 175 ℃, the cooling rate of the gas phase trap is shown by the curve of the first in fig. 1, specifically, the different temperature ranges of the heating zone can enable the gas phase trap after the reaction to obtain different cooling rates, and further, the thickness and the size of the two-dimensional bismuth iodide single crystal are regulated and controlled.

S5, after the gas-phase trap is completely cooled, collecting powder attached to the fluorophlogopite substrate to obtain a two-dimensional bismuth iodide single crystal; the two-dimensional bismuth iodide single crystal has a size of 1000 μm and a thickness of 500 nm.

Example 2:

the preparation method of the large-size two-dimensional bismuth iodide single crystal of the embodiment 2 of the invention comprises the following steps:

s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on the corundum boat to form a gas-phase trap; wherein the amount of bismuth iodide powder added was 0.5 g.

S2, placing the gas-phase trap at the central position of the tube furnace, and heating to make the bismuth iodide powder reach the volatilization temperature; specifically, the opening direction of the corundum boat is opposite to the gas flow direction of the introduced argon and hydrogen, and the volatilization temperature is 330 ℃.

S3, introducing argon and hydrogen into the tube furnace, diluting the gasified bismuth iodide in a constant-temperature environment, and carrying out reduction reaction; argon gas is introduced as a diluent gas, and hydrogen gas is introduced as a reducing gas. Specifically, the time of the reduction reaction was 10min, the flow rate of introduced argon gas was 50sccm, and the flow rate of introduced hydrogen gas was 20 sccm.

S4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process; preferably, the heating zone at the end of the tube furnace is in gradient distribution, the temperature range is 25-175 ℃, in this embodiment, the gas phase trap is placed at the heating zone with the temperature of 125 ℃, the cooling rate of the gas phase trap is shown by a curve of the second step in fig. 1, specifically, the different temperature ranges of the heating zone can enable the gas phase trap after the reaction to obtain different cooling rates, and further, the thickness and the size of the two-dimensional bismuth iodide single crystal are regulated and controlled.

S5, after the gas-phase trap is completely cooled, collecting powder attached to the fluorophlogopite substrate to obtain a two-dimensional bismuth iodide single crystal; the two-dimensional bismuth iodide single crystal has a size of 500 μm and a thickness of 200 nm.

Example 3:

the preparation method of the large-size two-dimensional bismuth iodide single crystal in the embodiment 3 of the invention comprises the following steps:

s1, placing bismuth iodide powder into a corundum boat with an opening at one end, and then reversely buckling the fluorophlogopite substrate on the corundum boat to form a gas-phase trap; wherein the amount of bismuth iodide powder added was 0.1 g.

S2, placing the gas-phase trap at the central position of the tube furnace, and heating to make the bismuth iodide powder reach the volatilization temperature; specifically, the opening direction of the corundum boat is opposite to the airflow direction of the introduced argon and hydrogen, and the volatilization temperature is 280 ℃.

S3, introducing argon and hydrogen into the tube furnace, diluting the gasified bismuth iodide in a constant-temperature environment, and carrying out reduction reaction; argon gas is introduced as a diluent gas, and hydrogen gas is introduced as a reducing gas. Specifically, the time of the reduction reaction is 5min, the flow of introduced argon gas is 100sccm, and the flow of introduced hydrogen gas is 50 sccm.

S4, after the reaction is finished, moving the gas-phase trap to a heating belt at the tail end of the tube furnace for cooling, and depositing the gas in the corundum boat on the fluorophlogopite substrate to form adhesion in the cooling process; preferably, the heating zone at the end of the tube furnace is in gradient distribution, the temperature range is 25-175 ℃, in this embodiment, the gas phase trap is placed at the heating zone with the temperature of 25 ℃, the cooling rate of the gas phase trap is shown as a curve in a graph 1, specifically, the different temperature ranges of the heating zone enable the gas phase trap after the reaction to obtain different cooling rates, and further, the thickness and the size of the two-dimensional bismuth iodide single crystal are regulated and controlled.

S5, after the gas-phase trap is completely cooled, collecting powder attached to the fluorophlogopite substrate to obtain a two-dimensional bismuth iodide single crystal; the two-dimensional bismuth iodide single crystal has a size of 200 μm and a thickness of 5 nm.

Comparative example 1:

this comparative example, which uses a corundum boat with two open ends instead of a corundum boat with one open end to emphasize the importance of gas phase traps, was prepared by a method comprising the steps of:

1) under the atmosphere of normal pressure, the fluorophlogopite substrate is reversely buckled on a corundum boat which contains 0.5g of bismuth iodide powder and is provided with openings at two ends, and the corundum boat is placed in the center of a tube furnace;

2) heating the tubular furnace to 330 ℃, setting the argon flow to be 50sccm and the hydrogen to be 20sccm, and keeping the temperature for 10 min;

3) the gas phase trap is moved to the heating zone, the temperature of the heating zone is set to be 25 ℃, the cooling rate of the gas phase trap is shown as a curve (r) in fig. 1, the gas phase trap can be taken out after being cooled to the room temperature, and in the embodiment, the taken-out fluorophlogopite substrate is not attached with the two-dimensional bismuth iodide single crystal, namely, the two-dimensional bismuth iodide single crystal cannot be obtained.

Comparative example 2:

this comparative example uses Si and Al₂O₃The preparation method comprises the following steps of:

1) in the atmosphere of normal pressure, Si and Al are mixed₂O₃The soda-lime glass or graphene substrate is respectively reversely buckled on a corundum boat which is filled with 0.5g of bismuth iodide powder and is provided with an opening at one end, the whole body is arranged in the center of the tube furnace, and the opening direction is opposite to the air flow direction;

2) heating the tubular furnace to 330 ℃, setting the argon flow to be 50sccm and the hydrogen to be 20sccm, and keeping the temperature for 10 min;

and 3, moving the gas-phase trap to a heating belt, setting the temperature of the heating belt to be 25 ℃, and taking out the gas-phase trap after the gas-phase trap is cooled to room temperature at the time as shown by a curve (r) in the figure 1.

Bismuth iodide and Al with the size less than 40 mu m can be obtained on the taken-out Si, graphene and soda-lime glass substrate₂O₃Bismuth iodide could not be obtained, and it can be seen that bismuth iodide could indeed be obtained using Si, graphene and soda-lime glass substrates, but the size thereof was consistent with that of general production, and could not reach the product to be obtained by the present invention, whereas Al was a product obtained by the present invention₂O₃Bismuth iodide was not obtained on the substrate.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.