阅读说明：本技术 介质衬底上直接生长二维六方氮化硼的方法 (Method for directly growing two-dimensional hexagonal boron nitride on dielectric substrate ) 是由 孟军华 张兴旺 高孟磊 尹志岗 吴金良 于 2019-10-18 设计创作，主要内容包括：本发明公开了一种介质衬底上直接生长二维六方氮化硼的方法。该方法包括：准备一介质衬底；将所述介质衬底预置在一离子束溅射沉积腔室内,沉积腔室内包含氮化硼靶,以及辅助离子源和主离子源,并将该沉积腔室预抽至一背底真空度；该辅助离子源对介质衬底表面实施原位氮化处理；该主离子源溅射该氮化硼靶得到氮、硼原子并沉积至该介质衬底上生长二维六方氮化硼；降温得到二维六方氮化硼样品。本发明提供的介质衬底上直接生长二维六方氮化硼的方法,不仅可以提高介质衬底上六方氮化硼的晶体质量,而且可控性好,制备的薄膜表面平整、均匀性好,对其光电子学应用有着十分重要的意义。(The invention discloses a method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate. The method comprises the following steps: preparing a dielectric substrate; presetting the dielectric substrate in an ion beam sputtering deposition chamber, wherein the deposition chamber contains a boron nitride target, an auxiliary ion source and a main ion source, and pre-pumping the deposition chamber to a background vacuum degree; the auxiliary ion source carries out in-situ nitridation treatment on the surface of the dielectric substrate; the main ion source sputters the boron nitride target to obtain nitrogen and boron atoms, and the nitrogen and boron atoms are deposited on the dielectric substrate to grow two-dimensional hexagonal boron nitride; and cooling to obtain a two-dimensional hexagonal boron nitride sample. The method for directly growing the two-dimensional hexagonal boron nitride on the dielectric substrate provided by the invention not only can improve the crystal quality of the hexagonal boron nitride on the dielectric substrate, but also has good controllability, and the prepared film has flat surface and good uniformity, thereby having very important significance for the application of optoelectronics.)

1. A method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate is characterized by comprising the following steps:

preparing a dielectric substrate;

presetting the dielectric substrate in an ion beam sputtering deposition chamber, wherein the deposition chamber comprises a boron nitride target, an auxiliary ion source and a main ion source, and pre-pumping the deposition chamber to a background vacuum degree;

the auxiliary ion source carries out in-situ nitridation treatment on the surface of the dielectric substrate;

the main ion source sputters the boron nitride target to obtain nitrogen and boron atoms, and the nitrogen and boron atoms are deposited on the dielectric substrate to grow two-dimensional hexagonal boron nitride;

and cooling to obtain a two-dimensional hexagonal boron nitride sample.

2. The method of claim 1, wherein the preparing a dielectric substrate comprises:

and sequentially placing the medium substrate in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning, and drying by using nitrogen.

3. The method for directly growing two-dimensional hexagonal boron nitride on the dielectric substrate according to claim 1 or 2, wherein the dielectric substrate is made of: al (Al)₂O₃、SiO₂Si, quartz or strontium titanate.

4. The method for directly growing two-dimensional hexagonal boron nitride on the dielectric substrate according to claim 1, wherein the background vacuum degree is 1 x 10^-4Pa or less.

5. The method of claim 1, wherein the purity of the boron nitride target is greater than 99.5%.

6. The method of claim 1, wherein the in-situ nitridation of the surface of the dielectric substrate by the auxiliary ion source comprises:

heating the dielectric substrate to a first target temperature;

and introducing nitrogen into the deposition chamber, and generating nitrogen ion beams by the action of the auxiliary ion source to perform nitridation treatment on the surface of the medium substrate.

7. The method as claimed in claim 6, wherein the first target temperature is between room temperature and 1000 ℃, the flow rate of the nitrogen gas is between 4sccm and 20sccm, the operating voltage of the auxiliary ion source is between 300V and 600V, and the ion beam current density of the nitrogen ion beam is between 0.05mA/cm²To 0.2mA/cm²The time of the nitridation treatment is between 3min and 20 min.

8. The method of claim 1, wherein the sputtering of the boron nitride target by the main ion source to obtain nitrogen and boron atoms comprises:

heating the dielectric substrate to a second target temperature;

and introducing nitrogen into the deposition chamber, and generating nitrogen ion beams under the action of the main ion source to sputter the boron nitride target to obtain nitrogen and boron atoms.

9. The method of claim 8, wherein the second target temperature is between 700 ℃ and 1300 ℃, the flow rate of the nitrogen gas is between 4sccm and 20sccm, the operating voltage of the main ion source is between 800V and 1500V, and the ion beam current density of the nitrogen ion beam is between 0.1mA/cm²To 0.4mA/cm²In the growth of the two-dimensional hexagonal boron nitrideThe time is between 10min and 60 min.

10. A two-dimensional hexagonal boron nitride grown directly on a dielectric substrate by the method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of material science, in particular to a method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate.

Background

In recent years, two-dimensional layered materials have been studied due to their thickness at atomic level, unique low-dimensional structure, and many excellent physical, chemical, and electronic properties. As the only two-dimensional insulator material, hexagonal boron nitride (h-BN) has become a hot spot of recent research by researchers at home and abroad.

h-BN has a layered structure similar to graphene, with B, N atoms in the layer in sp²The hybrid mode forms covalent bonds, and the layers are bonded together by van der waals forces. The highly similar crystal structures enable the two to have certain common characteristics, such as extremely high in-plane elastic modulus, high thermal conductivity, good chemical stability and the like; and the difference of the nuclear electron arrangement makes the energy band structure and the photoelectric property of the two have obvious difference: graphene is a semimetal with zero band gap, and h-BN has the forbidden band width as high as 5.97eV, so that the graphene has good electrical insulation. Due to the layered atomic arrangement and the in-plane ionic crystal composition, the h-BN surface has few dangling bonds and charge traps, and the h-BN has the same SiO structure₂The close dielectric constant and breakdown field make it attractive as a substrate or gate dielectric material for graphene or other two-dimensional atomic crystals. In addition, the h-BN with the wide band gap has very high absorption coefficient for ultraviolet light with energy higher than the band gap width, and has wide application prospect in the aspects of preparing deep ultraviolet light for luminescence, detection and the like.

The preparation of high-quality h-BN material is the basis and precondition for the property research and the device application. At present, transition metal is generally used as a substrate when h-BN is grown, and the h-BN needs to be transferred to other medium substrates for material characterization or device preparation. The transfer process not only easily causes wrinkles, defects or mechanical damage to the surface of the h-BN film, but also causes pollution to the h-BN by the residues of organic matters, thereby seriously affecting the performance of devices. Therefore, the realization of the direct growth of the high-quality h-BN two-dimensional atomic crystal on the dielectric substrate has important significance for the application of the high-quality h-BN two-dimensional atomic crystal. Because the substrate lacks catalytic activity, the h-BN on the dielectric substrate needs higher activation energy for nucleation, so that the h-BN on the dielectric substrate has the problems of difficult nucleation, nonuniform nucleation, limited crystal quality, smaller crystal domain size and the like.

Disclosure of Invention

Technical problem to be solved

In order to solve one or more of the problems, the invention provides a method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate.

(II) technical scheme

According to one aspect of the invention, a method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate is provided, and the method comprises the following steps:

preparing a dielectric substrate;

presetting the dielectric substrate in an ion beam sputtering deposition chamber, wherein the deposition chamber comprises a boron nitride target, an auxiliary ion source and a main ion source, and pre-pumping the deposition chamber to a background vacuum degree;

the auxiliary ion source carries out in-situ nitridation treatment on the surface of the dielectric substrate;

sputtering a boron nitride target by a main ion source to obtain nitrogen and boron atoms, and depositing the nitrogen and boron atoms on the dielectric substrate to grow two-dimensional hexagonal boron nitride;

and cooling to obtain a two-dimensional hexagonal boron nitride sample.

Wherein:

in some embodiments, preparing a dielectric substrate comprises:

and sequentially placing the medium substrate in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning, and drying by using nitrogen.

Further, the dielectric substrate is made of the following materials: al (Al)₂O₃、SiO₂Si, quartz or strontium titanate.

In some embodiments, the degree of vacuum on the back side is 1 × 10^-4Pa or less.

In some embodiments, the purity of the nitrogen and boron atoms in the boron nitride target is greater than 99.5%.

In some embodiments, the in-situ nitridation of the surface of the dielectric substrate by the auxiliary ion source comprises:

heating the dielectric substrate to a first target temperature;

introducing nitrogen into the deposition chamber, and generating nitrogen ion beams by the action of an auxiliary ion source to nitride the surface of the medium substrate, wherein the step further comprises the following steps:

the first target temperature is between room temperature and 1000 ℃, the flow rate of nitrogen is between 4sccm and 20sccm, the working voltage of the auxiliary ion source is between 300V and 600V, and the ion beam current density of the nitrogen ion beam is between 0.05mA/cm²To 0.2mA/cm²The time of the nitriding treatment is between 3min and 20 min.

In some embodiments, sputtering the boron nitride target by the primary ion source to obtain nitrogen and boron atoms comprises:

heating the dielectric substrate to a second target temperature;

introducing nitrogen into the deposition chamber, generating nitrogen ion beams under the action of a main ion source to sputter a boron nitride target to obtain nitrogen and boron atoms, and further, in the step:

the second target temperature is between 700 ℃ and 1300 ℃, the flow rate of nitrogen is between 4sccm and 20sccm, the working voltage of the main ion source is between 800V and 1500V, and the ion beam current density of the nitrogen ion beam is between 0.1mA/cm²To 0.4mA/cm²The growth time of the two-dimensional hexagonal boron nitride is between 10min and 60 min.

According to another aspect of the present invention, there is provided a two-dimensional hexagonal boron nitride grown directly on a dielectric substrate by the above method.

(III) advantageous effects

According to the technical scheme, the method for directly growing the two-dimensional hexagonal boron nitride on the dielectric substrate has the following beneficial effects:

(1) the invention realizes the direct growth of h-BN on the dielectric substrate, and can avoid the complicated transfer process and the problems of film damage and pollution caused by transfer;

(2) the method carries out in-situ surface nitridation treatment on the substrate by ion beam sputtering and simultaneously adopts nitrogen ion beam sputtering to deposit h-BN, so that the nucleation of the h-BN can be effectively promoted, the nitrogen ion beam can provide sufficient nitrogen source, the crystal quality of the h-BN is improved, and the method has very important significance for the photoelectronics application. In addition, the ion beam sputtering deposition method has good controllability, and the prepared film has smooth surface and good uniformity.

Drawings

FIG. 1 is a flow chart of direct growth of two-dimensional h-BN on a dielectric substrate according to an embodiment of the invention;

FIG. 2 is a schematic diagram of an apparatus for directly growing two-dimensional h-BN on a dielectric substrate according to the invention;

FIG. 3 is a UV-Vis spectrum of two-dimensional h-BN grown directly on a dielectric substrate according to an embodiment of the invention;

FIG. 4 is an atomic force microscope topography of a two-dimensional h-BN film fabricated on a dielectric substrate in accordance with an embodiment of the invention.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

The invention adopts ion beam assisted deposition technology to directly grow two-dimensional h-BN on the dielectric substrate, promotes the nucleation of the h-BN on the dielectric substrate by ion beam in-situ nitridation treatment of the surface of the substrate, simultaneously adopts nitrogen ion beam sputtering to grow the h-BN, provides sufficient nitrogen source, improves the crystallization quality of the h-BN film, and thus directly grows the h-BN two-dimensional atomic crystal on the dielectric substrate.

It should be noted that in the drawings or description, the same drawing reference numerals are used for similar or identical parts. Implementations not depicted or described in the drawings are of a form known to those of ordinary skill in the art. Additionally, while exemplification of parameters including particular values may be provided herein, it is to be understood that the parameters need not be exactly equal to the respective values, but may be approximated to the respective values within acceptable error margins or design constraints.

In view of the above, in one aspect, the present invention provides a method for directly growing two-dimensional hexagonal boron nitride on a dielectric substrate, and fig. 1 shows a flowchart of the method for directly growing two-dimensional h-BN on the dielectric substrate according to the present invention. As shown in fig. 1, the method comprises the following specific steps:

step A, preparing a dielectric substrate.

In some embodiments, the step a comprises:

the method comprises the following steps of sequentially placing a medium substrate in acetone, isopropanol, ethanol and deionized water for ultrasonic cleaning, then drying by nitrogen, and installing the medium substrate into an ion beam sputtering deposition chamber for later use, wherein the deposition chamber comprises a boron nitride target, an auxiliary ion source and a main ion source, and is pre-pumped to a background vacuum degree.

The dielectric substrate in this step is selected from one of the following materials: al (Al)₂O₃、SiO₂Si, quartz, strontium titanate.

And step B, carrying out in-situ nitridation treatment on the surface of the dielectric substrate by an auxiliary ion source. FIG. 2 is a schematic diagram of an apparatus for directly growing two-dimensional h-BN on a dielectric substrate according to the invention. As shown in fig. 2, the deposition chamber contains two ion sources (a main ion source and an auxiliary ion source) and a pre-positioned boron nitride target, wherein the auxiliary ion source is used for substrate surface nitridation and the main ion source is used for h-BN growth.

In some embodiments, step B further comprises:

substep B1, pre-pumping the deposition chamber to a background vacuum of 1X 10^-4Pa below;

substep B2, heating the dielectric substrate to a first target temperature, wherein the first target temperature is between room temperature and 1000 ℃, preferably, in the present embodiment, the temperature of the dielectric substrate is 700 ℃;

and a substep B3, introducing nitrogen gas into the deposition chamber, and generating nitrogen ion beams by the action of an auxiliary ion source to directly nitrify and process the surface of the medium substrate, wherein:

the flow rate of the nitrogen is between 4sccm and 20sccm, the preferred flow rate of the nitrogen is 10sccm, the working voltage of the auxiliary ion source is between 300V and 600V, the preferred working voltage is 500V, and the ion beam current density of the nitrogen ion beam is 0.05mA/cm²To 0.2mA/cm²Preferably from each otherThe beamlet density is 0.05mA/cm²The time of the nitriding treatment is between 3min and 20min, and the preferable time of the nitriding treatment is 10 min.

In this embodiment, based on the above-described preferred embodiment, in the specific preparation process, the flow rate of nitrogen gas is 10sccm, the temperature of the dielectric substrate is 700 ℃, the operating voltage of the auxiliary ion source is 500V, and the ion beam current density of the nitrogen ion beam is 0.05mA/cm²And the nitridation treatment time is 10min, so that the effect of promoting the nucleation of the h-BN on the dielectric substrate through the ion beam in-situ nitridation treatment on the surface of the substrate is realized.

And step C, sputtering a boron nitride target by a main ion source to obtain nitrogen and boron atoms, and depositing the nitrogen and boron atoms on the dielectric substrate to grow the two-dimensional hexagonal boron nitride.

In some embodiments, this step C further comprises:

substep C1, the auxiliary ion source nitrogen was turned off and the deposition chamber background vacuum was restored to 1X 10^-4Pa below;

substep C2, heating the dielectric substrate to a second target temperature, wherein the second target temperature is between 700 ℃ and 1000 ℃, preferably the substrate temperature is 1200 ℃;

and a substep C3 of introducing nitrogen into the deposition chamber, and generating a nitrogen ion beam by the action of the main ion source to sputter the boron nitride target to obtain nitrogen and boron atoms, wherein the substep comprises the following steps:

the temperature of the medium substrate (i.e. the second target temperature) is between 700 ℃ and 1300 ℃, the preferable substrate temperature is 1200 ℃, the flow rate of the nitrogen gas is between 4sccm and 20sccm, the preferable flow rate of the nitrogen gas is 10sccm, the working voltage of the main ion source is between 800V and 1500V, the preferable working voltage is 1000V, and the ion beam current density of the nitrogen ion beam is 0.1mA/cm²To 0.4mA/cm²Preferably, the ion beam current density is 0.2mA/cm²The growth time of the two-dimensional hexagonal boron nitride is between 10min and 60min, and the preferable growth time is 30 min.

In this embodiment, based on the above-mentioned best mode, the flow rate of nitrogen is 10sccm, the substrate temperature is 1200 ℃, the working voltage of the main ion source is 1000V, and the nitrogen ions are generated during the specific preparation processThe ion beam current density of the beam is 0.2mA/cm²The growth time is 30min, so that the h-BN is grown by adopting nitrogen ion beam sputtering, a sufficient nitrogen source is provided, and the crystallization quality of the h-BN film is improved.

And D, after the growth is finished, cooling the hexagonal boron nitride deposited on the medium substrate to obtain a two-dimensional h-BN sample.

Based on the foregoing embodiment, another aspect of the present invention provides a two-dimensional hexagonal boron nitride, which is obtained by directly growing on a dielectric substrate by the foregoing method, and a specific growth method is already embodied in the foregoing embodiments and is not described herein again.

By the method for directly growing the two-dimensional hexagonal boron nitride on the dielectric substrate provided by the invention and the embodiment thereof, as shown in fig. 3, which is an ultraviolet-visible absorption spectrogram of the two-dimensional h-BN prepared according to the embodiment of the invention, a strong absorption peak can be observed at 200nm, and the strong absorption peak corresponds to a characteristic peak of the h-BN. FIG. 4 is an Atomic Force Microscope (AFM) morphology of the h-BN film prepared according to the embodiment of the invention, and it can be seen that the surface of the film is very flat and uniform.

So far, the method for directly growing the two-dimensional h-BN on the dielectric substrate is introduced.

In conclusion, the method for directly growing the two-dimensional h-BN on the dielectric substrate can simply and efficiently realize the direct growth of the h-BN two-dimensional atomic crystal on the dielectric substrate, avoid the complicated transfer process and the problems of film damage and pollution caused by transfer, carry out in-situ surface nitridation treatment on the substrate through ion beam sputtering and simultaneously adopt nitrogen ion beam sputtering to deposit the h-BN, can effectively promote the nucleation of the h-BN and improve the crystal quality of the h-BN, and the prepared film has smooth surface and good uniformity and has very important significance for the application of the photoelectronics.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.