阅读说明：本技术 六方氮化硼薄膜及其制备方法 (Hexagonal boron nitride film and preparation method thereof ) 是由 赵昱 王浩 杨晓霞 王文龙 白雪冬 于 2019-02-15 设计创作，主要内容包括：本发明提供一种制备六方氮化硼薄膜的方法,包括如下步骤：(1)将硼源置于衬底中；(2)在惰性气体气氛下,将所述硼源升温至硼源熔融；(3)然后,通入气相氮源进行反应；(4)反应完成后,除去未反应的硼源,得到六方氮化硼薄膜。同时,本发明还提供本发明的制备方法制得的六方氮化硼薄膜。本发明制备六方氮化硼薄膜的方法简单易操作,且通过本发明的制备方法制得的六方氮化硼薄膜宏观上连续、均匀、面积大又平整。(The invention provides a method for preparing a hexagonal boron nitride film, which comprises the following steps: (1) placing a boron source in a substrate; (2) heating the boron source to melt the boron source under the inert gas atmosphere; (3) then, introducing a gas phase nitrogen source for reaction; (4) and after the reaction is finished, removing the unreacted boron source to obtain the hexagonal boron nitride film. Meanwhile, the invention also provides the hexagonal boron nitride film prepared by the preparation method. The method for preparing the hexagonal boron nitride film is simple and easy to operate, and the hexagonal boron nitride film prepared by the preparation method is continuous, uniform, large in area and flat in macro.)

1. A method of making a hexagonal boron nitride film, comprising the steps of:

(1) placing a boron source in a substrate;

(2) heating the boron source to melt the boron source under the inert gas atmosphere;

(3) then, introducing a gas phase nitrogen source for reaction;

(4) and after the reaction is finished, removing the unreacted boron source to obtain the hexagonal boron nitride film.

2. The method of claim 1, wherein the boron source is one or more of boron oxide, boric acid, lithium metaborate, sodium metaborate, potassium metaborate, lithium tetraborate and hydrates thereof, sodium tetraborate and hydrates thereof, potassium tetraborate and hydrates thereof, and aluminum tetraborate and hydrates thereof;

preferably, the inert gas is helium, neon or argon.

3. The method of claim 1, wherein the substrate is one or more of a sapphire sheet, a silicon carbide sheet, a polycrystalline aluminum oxide sheet, a graphite sheet, a boron nitride sheet, a silicon carbide crucible, a polycrystalline alumina crucible, a graphite crucible, and a boron nitride crucible.

4. The method of claim 1, wherein the vapor phase nitrogen source is ammonia or nitrogen.

5. The method according to claim 1, wherein the inert gas atmosphere in the step (2) has a flow rate of 100 to 1000 sccm.

6. The method according to claim 1, wherein the temperature increase in the step (2) is performed at a temperature increase rate of 10 ℃/min to 20 ℃/min;

preferably, the temperature rise in the step (2) is to a temperature higher than the melting point of the boron source and lower than the boiling point of the boron source;

preferably, the temperature rise in the step (2) is to 700 ℃ -1180 ℃.

7. The method according to claim 1, wherein the flow rate of the vapor phase nitrogen source in the step (3) is 0.1sccm to 2000 sccm;

preferably, the reaction in step (3) is carried out for 10s to 10 h.

8. The method of claim 1, wherein the method further comprises the steps of: and (4) after the reaction in the step (4) is finished, cooling to room temperature under an inert gas atmosphere.

9. The method of claim 1, wherein the removing of the unreacted boron source in step (4) is performed by a method comprising:

A. heating the product after the reaction to a temperature above the melting point of the boron source under the pressure less than or equal to 1Pa, preserving the temperature for 1-2 h, and pumping away the residual boron source; or

B. And coating a layer of anisole solution of polymethyl methacrylate with the mass fraction of 1-10% on the surface of the product after the reaction is finished, soaking the solidified polymethyl methacrylate in alcohol or water, taking the product after the reaction with the polymethyl methacrylate to float on the liquid surface, removing the polymethyl methacrylate by using another substrate, washing and drying the product, and removing the polymethyl methacrylate by using acetone.

10. A hexagonal boron nitride film produced according to the method of any one of claims 1-9.

Technical Field

The invention belongs to the field of materials. In particular, the invention relates to a hexagonal boron nitride film and a preparation method thereof.

Background

Hexagonal boron nitride (h-BN) is a group III-V compound whose hexagonal phase has a layered structure similar to that of graphene, known as white graphite. B, N atoms in the layer are bonded together by covalent bonds, and the structure is stable; the layers are bonded by van der waals forces and the layers can be opened by ultrasonic peeling. The hexagonal boron nitride material has many excellent physicochemical properties and has wide application in many fields. The hexagonal boron nitride is very stable in air, can resist the high temperature of 2000 ℃, can be combusted only under the continuous and strong heating condition, and can be applied to high-temperature refractory materials and refractory coatings. Hexagonal boron nitride is a typical anisotropic material, has higher thermal conductivity, low thermal expansion coefficient and high tensile strength in a plane, and can be applied to grinding tools and high-pressure equipment; the hexagonal boron nitride has the property of wide forbidden band, the band gap of the hexagonal boron nitride is about 6eV, and the hexagonal boron nitride can be applied to ultraviolet photoelectric devices.

The hexagonal boron nitride two-dimensional nanosheet layer material can be prepared by a top-down method. A macroscopic amount of BN two-dimensional nanosheet layer material is obtained by carrying out ultrasonic stripping on a bulk hexagonal boron nitride material, but the ultrasonic process is long in time consumption and limited in ultrasonic effect, a thin layer of BN needs to be obtained through centrifugal extraction, so that the yield is greatly reduced, and the thinned nanosheet layer is usually polymerized again in a solution, so that the efficiency is reduced. The bottom-up method (bottom-up) mainly includes two methods of CVD and PVD (physical vapor deposition). The CVD approach, in addition to the metal-catalyzed growth method, can also facilitate the reaction by a number of ancillary techniques. The PVD technology is to evaporate high-purity B source or BN source in vacuum environment, and bombard the substrate with H plasma or N plasma beam to synthesize BN film, commonly known as magnetron sputtering and radio frequency reactive sputtering. However, it is difficult to carry out a macro synthesis by either CVD or PVD.

Disclosure of Invention

The invention aims to provide a method which is simple and easy to operate and can effectively prepare a large-area continuous ultrathin hexagonal boron nitride film on a substrate. The invention also aims to provide a large-area continuous ultrathin hexagonal boron nitride film.

The purpose of the invention is realized by providing the following technical scheme.

In one aspect, the present invention provides a method for preparing a hexagonal boron nitride film, comprising the steps of:

(1) placing a boron source in a substrate;

(2) heating the boron source to melt the boron source under the inert gas atmosphere;

(3) then, introducing a gas phase nitrogen source for reaction;

(4) and after the reaction is finished, removing the unreacted boron source to obtain the hexagonal boron nitride film.

Preferably, in the method of the present invention, the boron source is one or more of boron oxide, boric acid, lithium metaborate, sodium metaborate, potassium metaborate, lithium tetraborate and hydrates thereof, sodium tetraborate and hydrates thereof, potassium tetraborate and hydrates thereof, and aluminum tetraborate and hydrates thereof.

Preferably, in the method of the present invention, the inert gas is helium, neon or argon.

Preferably, in the method of the present invention, the substrate is one or more of a sapphire sheet, a silicon carbide sheet, a polycrystalline aluminum oxide sheet, a graphite sheet, a boron nitride sheet, a silicon carbide crucible, a polycrystalline alumina crucible, a graphite crucible, and a boron nitride crucible.

Preferably, in the method of the present invention, the gaseous nitrogen source is ammonia gas or nitrogen gas.

Preferably, in the method of the present invention, the flow rate of the inert gas atmosphere in the step (2) is 100 to 1000 sccm.

Preferably, in the method of the present invention, the temperature increase in the step (2) is performed at a temperature increase rate of 10 ℃/min to 20 ℃/min.

Preferably, the temperature increase in the step (2) is to be higher than the melting point of the boron source and lower than the boiling point of the boron source.

Preferably, the temperature rise in the step (2) is to 700 ℃ -1180 ℃.

Preferably, in the method of the present invention, the flow rate of the gas phase nitrogen source in the step (3) is 0.1sccm to 2000 sccm.

Preferably, the reaction in step (3) is carried out for 10s to 10 h.

Preferably, in the method of the present invention, the method further comprises the steps of: and (4) after the reaction in the step (4) is finished, cooling to room temperature under an inert gas atmosphere.

Preferably, in the method of the present invention, the removing of the unreacted boron source in the step (4) is performed by a method including a high-temperature pump or a solution method. More specifically, in the method of the present invention, the removal of the unreacted boron source in the step (4) is performed by a method comprising the steps of:

A. heating the product after the reaction to a temperature above the melting point of the boron source under the pressure less than or equal to 1Pa, preserving the temperature for 1-2 h, and pumping away the residual boron source; or

B. Coating a layer of anisole solution of polymethyl methacrylate (PMMA) with the mass fraction of 1-10% on the surface of the product after the reaction is finished, soaking the solidified polymethyl methacrylate in alcohol or water, floating the product on the liquid surface with the polymethyl methacrylate after the reaction is finished, removing the polymethyl methacrylate by using another substrate, washing and drying the substrate, and removing the polymethyl methacrylate by using acetone.

In another aspect, the present invention provides a hexagonal boron nitride film produced by the method of the present invention.

The invention has the following beneficial effects:

the method for preparing the hexagonal boron nitride film is simple and easy to operate, and the hexagonal boron nitride film prepared by the preparation method is continuous, uniform, large in area and flat in macro.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a flow chart of a method of preparing a hexagonal boron nitride film according to one embodiment of the present invention;

FIG. 2 is a physical representation of a hexagonal boron nitride film on a sapphire substrate, prepared in example 1 of the present invention;

FIG. 3 is an optical microscope image (a) and a scanning electron microscope image (b) of a hexagonal boron nitride thin film prepared in example 1 of the present invention;

FIG. 4 is transmission electron micrographs (a) and (b), an electron diffraction pattern (c) and an electron energy loss spectrum (d) of the hexagonal boron nitride film prepared in example 1 of the present invention;

fig. 5 is an afm (a) of the hexagonal boron nitride film prepared in example 1 of the present invention on a sapphire substrate, an afm (b) of the hexagonal boron nitride film with an enlarged damaged boundary portion and a height curve (c) of the corresponding hexagonal boron nitride film (from left to right along a line segment in the (b) diagram);

FIG. 6 is an infrared spectrum of a hexagonal boron nitride film prepared in example 1 of the present invention;

FIG. 7 is a Raman spectrum of a hexagonal boron nitride film prepared in example 1 of the present invention;

FIG. 8 is an optical microscope photograph of a hexagonal boron nitride film produced in example 2 of the present invention;

FIG. 9 is an optical microscope photograph of a hexagonal boron nitride film produced in example 3 of the present invention;

FIG. 10 is an optical microscope photograph of a hexagonal boron nitride film produced in example 4 of the present invention;

FIG. 11 is an optical microscope photograph of a hexagonal boron nitride film produced in example 5 of the present invention;

FIG. 12 is an optical microscope photograph of a hexagonal boron nitride film produced in example 6 of the present invention.

Detailed Description

The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.