阅读说明：本技术 制备大面积过渡金属硫族化合物单晶的方法及其所得产品 (Method for preparing large-area transition metal chalcogenide single crystal and product obtained by method ) 是由 王欣然 李涛涛 施毅 于 2020-06-29 设计创作，主要内容包括：本发明公开了一种制备大面积过渡金属硫族化合物单晶的方法及其所得产品。该方法包括如下步骤：(1)提供一C面蓝宝石单晶体,其表面原子级台阶方向沿着晶体的M轴方向；(2)以步骤(1)切割后的蓝宝石单晶体为衬底,基于气相沉积法,在蓝宝石单晶体表面生成单向排列的过渡金属硫族化合物晶粒,且晶粒不断长大、相互拼接,得到大面积的过渡金属硫族化合物单晶。该方法制备的过渡金属硫族化合物单晶的晶体横向尺寸可达英寸级以上,仅受限于衬底的尺寸,且无晶界存在,完全满足器件集成的应用,在微纳器件、场效应晶体管、发光器件、光电探测、集成电路等领域有着巨大的应用前景。(The invention discloses a method for preparing large-area transition metal chalcogenide single crystals and an obtained product. The method comprises the following steps: (1) providing a C-plane sapphire single crystal, wherein the surface atomic step direction of the C-plane sapphire single crystal is along the M-axis direction of the crystal; (2) and (2) taking the sapphire single crystal cut in the step (1) as a substrate, generating unidirectionally arranged transition metal chalcogenide crystal grains on the surface of the sapphire single crystal based on a vapor deposition method, and continuously growing and mutually splicing the crystal grains to obtain a large-area transition metal chalcogenide single crystal. The transverse size of the crystal of the transition metal chalcogenide monocrystal prepared by the method can reach inch level or above, is only limited by the size of the substrate, has no crystal boundary, completely meets the application of device integration, and has great application prospect in the fields of micro-nano devices, field effect transistors, light-emitting devices, photoelectric detection, integrated circuits and the like.)

1. A method for preparing a large-area transition metal chalcogenide single crystal, comprising the steps of:

(1) providing a C-plane sapphire single crystal, wherein the surface atomic step direction of the C-plane sapphire single crystal is along the M-axis direction of the crystal;

(2) and (2) taking the sapphire single crystal in the step (1) as a substrate, generating unidirectionally arranged transition metal chalcogenide crystal grains on the surface of the sapphire single crystal based on a vapor deposition method, and continuously growing and mutually splicing the crystal grains to obtain the large-area transition metal chalcogenide single crystal.

2. The method of preparing a large area transition metal chalcogenide single crystal according to claim 1, wherein the transition metal chalcogenide is molybdenum disulfide, tungsten disulfide, molybdenum diselenide, or tungsten diselenide.

3. The method for preparing a large area transition metal chalcogenide single crystal according to claim 1, wherein in step (1), the direction of atomic level step on the surface of the sapphire single crystal isOrientation, allowable angular deviation is ± 19.1 °.

4. The method for producing a large-area transition metal chalcogenide single crystal according to claim 1, wherein the sapphire single crystal in step (1) is obtained according to the following processing method: in the whole processing process of the sapphire self-picking rod, the sapphire is ensured to be cut obliquely along the A-axis direction, and the deviation angle caused by the cutting process to the M-axis direction does not exceed 34.6% of the inclination angle of the A-axis direction.

5. The method for preparing a large area transition metal chalcogenide single crystal according to claim 1, wherein in the step (2), the vapor deposition method is a chemical vapor deposition method, a molecular beam epitaxy method, a pulsed laser deposition method or a magnetron sputtering method.

6. The method for preparing a large area transition metal chalcogenide single crystal according to claim 5, wherein the transition metal chalcogenide crystal is prepared using a chemical vapor deposition method in step (2): placing the cut sapphire single crystal in a vapor deposition chamber, loading a transition metal chalcogenide growth source, setting the reaction conditions of the growth source, and generating unidirectionally arranged transition metal chalcogenide grains on the surface of the sapphire single crystal substrate; then continuously introducing a growth source, gradually growing the crystal grains of the transition metal chalcogenide, and splicing the crystal grains to obtain large-area transition metal chalcogenide single crystals.

7. A single crystal of a transition metal chalcogenide prepared by the method of any one of claims 1 to 6.

Technical Field

The invention relates to a method for preparing large-area transition metal chalcogenide single crystal and an obtained product thereof, belonging to the technical field of inorganic nano materials.

Background

The transition metal chalcogenide is a typical two-dimensional semiconductor material, has many excellent physicochemical properties such as a band gap structure in a visible light range and high electron mobility, and has wide application prospects in various fields such as photoelectric detector devices, field effect transistors, micro-nano electronic devices and large-scale integrated circuits thereof. The stable and controllable preparation of large-area single crystal materials with the size of inch and above is the key of the integration of two-dimensional material devices.

With a typical transition metal chalcogenide MoS₂Materials for example, currently, device-level MoS is prepared₂The material may be formed by a mechanical lift-off method, a Chemical Vapor Deposition (CVD) method, a molecular number epitaxy (MBE) method, or the like. Wherein the MoS obtained by mechanical stripping₂The method has high crystallization quality, but cannot obtain a large-area thin film material with uniform thickness, has low yield, and cannot meet the application of device integration.

The CVD method adopts gas containing Mo and S to react at high temperature, so that discretely distributed single-layer MoS can be obtained on the surface of the substrate₂Crystalline, or large area continuous polycrystalline films. Currently, CVD process yields individual MoS₂The size of the crystal grains is between 0.5 mu m and 1mm, and the directions of the crystal grains are randomly distributed (SiO)₂Amorphous substrates such as Si substrates and quartz), or substrates arranged in a 180 ° mirror-inverted state (6-fold symmetric substrates such as boron nitride substrates, mica substrates and ordinary C-plane sapphire). These MoS's are randomly arranged or arranged with 180 DEG mirror inversion₂When the crystals are spliced to form a large-area continuous film, different types of grain boundaries can be formed at the spliced positions. In the application of electronic devices, the grain boundary can cause serious electron scattering, so that the electron mobility is reduced, the on-state current and the on-off ratio are further reduced, and the overall performance of the device is greatly influenced.

Therefore, it is the current key technical difficulty to eliminate the grain boundary and obtain the large-size transition metal chalcogenide single crystal which can meet the integration application of the device.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems that the size of the transition metal chalcogenide single crystal prepared by the existing method is too small to meet the integration application of devices, or only large-area continuous polycrystalline materials can be obtained, and the performance of the devices is influenced by polycrystalline grain boundaries, the invention provides a method for preparing the large-area transition metal chalcogenide single crystal and the transition metal chalcogenide single crystal prepared by the method.

The technical scheme is as follows: the method for preparing the large-area transition metal chalcogenide single crystal comprises the following steps of:

(1) providing a C-plane sapphire single crystal, wherein the surface atomic step direction of the C-plane sapphire single crystal is along the M-axis direction of the crystal;

(2) and (2) taking the sapphire single crystal in the step (1) as a substrate, generating unidirectionally arranged transition metal chalcogenide crystal grains on the surface of the sapphire single crystal based on a vapor deposition method, and continuously growing the crystal grains and splicing the crystal grains to obtain the large-area transition metal chalcogenide single crystal.

The transition metal chalcogenide related by the method can be molybdenum disulfide, tungsten disulfide, molybdenum diselenide or tungsten diselenide and the like.

Specifically, the surface atomic level step direction of the sapphire single crystal provided in the step (1) isThe allowable angle deviation is +/-19.1 degrees, namely the surface atomic step direction of the sapphire single crystal provided in the step (1) is approximately along the M-axis direction of the crystal within the acceptable angle deviation range, the aim of the invention can be achieved, and the large-area transition metal chalcogenide single crystal is obtained.

Preferably, the sapphire crystal with the specific surface atomic level step direction in the step (1) can be obtained according to the following processing method: in the whole machining process of sapphire self-tapping, C-plane sapphire is obliquely cut along the A-axis direction, and due to machining errors, in the oblique machining process along the A-axis direction, the M-axis direction inevitably has a certain inclination, so that the deviation angle caused by the cutting process to the M-axis direction is ensured not to exceed 34.6% of the inclination angle of the A-axis direction.

Optionally, the deviation angle caused by the cutting process to the M-axis direction does not exceed 20% of the inclination angle of the a-axis direction; accordingly, the surface of a sapphire single crystalThe surface atomic level step direction is

Direction, allowable angular deviation ± 11 °.

In the step (2), the vapor deposition method can be a chemical vapor deposition method, a molecular beam epitaxy method, a pulsed laser deposition method, a magnetron sputtering method and the like.

Wherein, the process of preparing the transition metal chalcogenide crystal by adopting a chemical vapor deposition method comprises the following steps: placing the sapphire single crystal substrate in a chemical vapor deposition chamber, adding a transition metal chalcogenide growth source, setting the reaction conditions of the growth source, and generating unidirectionally arranged transition metal chalcogenide grains on the surface of the sapphire single crystal substrate; then continuously introducing a growth source, gradually growing the crystal grains of the transition metal chalcogenide, and splicing the crystal grains to obtain large-area transition metal chalcogenide single crystals.

With a transition metal chalcogenide MoS₂For example, the growth source includes a Mo source and an S source, which may be in a gas form, a solid form or a liquid form, and are gasified by evaporation, volatilization or the like, and enter the reaction chamber to perform a gas phase reaction. Wherein the Mo source is selected from MoO₃、MoO₂、Mo(CO)₆Inorganic salt of Mo, organic salt of Mo and complex thereof, in-situ oxidation product of Mo simple substance, and the like, wherein the S source can be selected from S simple substance steam, H₂S gas, and the like. The Mo source and the S source can react at the temperature of 750-1100 ℃ to generate MoS₂And crystallizing and depositing on the surface of the sapphire single crystal substrate.

The single crystal of transition metal chalcogenide according to the present invention is composed of continuous, unidirectionally arranged crystal grains of transition metal chalcogenide having a lateral dimension of at least inch.

The invention principle is as follows: in MoS₂The principles of the invention are illustrated by way of example. MoS₂Is C₃Symmetrical crystals of formula C₆The symmetrical C-plane sapphire surface is epitaxially grown (the influence of steps is not considered), 2 epitaxial directions with equivalent energy exist, and crystal grains with equal quantity and opposite arrangement can be obtained; book (I)The invention designs the atomic step direction of the surface of the substrate by utilizing the principle of surface step induced nucleation so as to ensure that the atomic step direction is in MoS₂During nucleation, the nucleation energy in one direction is lower than that in the other direction, so that only one oriented crystal grain can be generated and grown during nucleation. The surface step direction of the C-plane sapphire substrate in the industry is mainly along theI.e., the A-axis direction of the substrate, the steps in this direction for MoS in these 2 directions₂The energies of grain nucleation are equal, 2-directional MoS₂Grains are formed and grown with equal probability to finally generate polycrystal MoS₂A crystal; the invention changes the step direction of the surface of the substrate into

The direction, i.e. the direction of the steps, being parallel to the M axis of the crystal, promoting only one of the directions MoS₂Nucleation and growth are carried out, nucleation in the other direction is inhibited, transition metal chalcogenide crystal grains arranged in a single direction are formed, atomic-level precise combination is finally realized, and large-area single crystal growth is realized.

Has the advantages that: compared with the prior art, the invention has the advantages that: (1) by adopting the method, large-area continuous transition metal chalcogenide single crystals can be epitaxially grown on the substrate, the transverse size of the prepared transition metal chalcogenide single crystals is only limited by the size of the substrate and can reach the inch level, and the application of device integration is completely met; (2) meanwhile, the obtained transition metal chalcogenide monocrystal has no crystal boundary, does not have negative influence on the performance of the device, and has great application prospect in the fields of micro-nano devices, field effect transistors, light-emitting devices, photoelectric detection, integrated circuits and the like; (3) the preparation method has simple process, can realize batch production, has high yield, does not have the pollution problem caused by noble metal substrates, and can be popularized and applied in the microelectronic and optoelectronic industries.

Drawings

FIG. 1 is a photomicrograph of unidirectionally aligned molybdenum disulfide grains of example 1;

FIG. 2 is a SHG mapping plot of unidirectionally aligned molybdenum disulfide grains of example 1;

FIG. 3 is a TEM image of unidirectionally arranged molybdenum disulfide grains of example 1;

FIG. 4 is a photograph of a wafer-level molybdenum disulfide single crystal grown in example 2;

FIG. 5 is SHG mapping at any position of the wafer-level molybdenum disulfide single crystal grown in example 2;

FIG. 6 is a Raman spectrum of a single crystal of molybdenum disulfide obtained by growth in example 2;

FIG. 7 is a photoluminescence spectrum of a molybdenum disulfide single crystal grown in example 2;

FIG. 8 shows MoS grown on a general sapphire substrate in example 2₂An SHG-plane scan of the crystal;

FIG. 9 shows a unidirectional MoS grown in example 3₂An optical photograph of (a);

FIG. 10 shows MoS grown in example 3₂Atomic force microscopy pictures of single crystals.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

The preparation method for preparing the large-area transition metal chalcogenide single crystal can be used for preparing the transition metal chalcogenide single crystals such as molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide and the like, can induce the transition metal chalcogenide to form single-direction crystal grains by changing the surface step direction of a common sapphire product in the industry and a specific step direction, and finally realizes precise atomic combination and large-area single crystal growth.

The lateral size of the prepared single crystal of transition metal chalcogenide is limited only by the size of the substrate, for example, sapphire on the order of inches can be used as the substrate, and single crystals of transition metal chalcogenide with the lateral size of up to the order of inches can be prepared.

The method specifically comprises the following steps:

(1) providing a C-plane sapphire single crystal, wherein the surface atomic step direction of the C-plane sapphire single crystal is along the M-axis direction of the crystal;

the surface atomic level step direction is along the M axis direction of the crystal, namely the surface atomic level step direction is

And (4) direction. The sapphire crystal with specific surface atomic level step direction can be obtained by cutting sapphire, and the finally processed surface atomic level step direction may deviate from an ideal state due to the inevitable error existing in the actual machining processAnd (4) direction. Through experimental measurement and calculation, the allowed angle deviation is +/-19.1 degrees, namely the surface atomic level step direction of the sapphire single crystal provided in the step (1) can achieve the aim of the invention within an acceptable angle deviation range and substantially along the M-axis direction of the crystal, and the large-area transition metal chalcogenide single crystal is obtained.

Sapphire processing requires that a rod is first cut from a larger column and then cut into pieces. And (3) ensuring that the C surface of the sapphire is inclined along the A axis direction and the M direction is not inclined in the whole processing process, and obtaining the sapphire crystal in the specific direction in the step (1). Specifically, the sapphire crystal with a specific surface atomic level step direction in the step (1) can be obtained according to the following processing method: in the whole machining process of sapphire self-tapping, C-plane sapphire is obliquely cut along the A-axis direction, and due to machining errors, in the oblique machining process along the A-axis direction, the M-axis direction inevitably has a certain inclination, so that the deviation angle caused by the cutting process to the M-axis direction is ensured not to exceed 34.6% of the inclination angle of the A-axis direction. For example, the design values for the machining are a tilt angle in the a direction of 0.2 degrees and a tilt angle in the M direction of 0 degrees, and the actual measurement results after the machining are 0.2 degrees in the a direction and 0.04 degrees in the M direction, where 0.04/0.2 is 20% and less than 34.6%, which are within an acceptable range; when the deviation angle caused to the M-axis direction is 34.6% of the inclination angle of the A-axis direction, arctan0.346 ≈ 19.1 DEG, namely the direction of the corresponding crystal surface atomic-level stepJust offDirection 19.1 deg., is the allowable deviation threshold.

(2) And (2) taking the sapphire single crystal cut in the step (1) as a substrate, and performing a vapor deposition method based on chemical vapor deposition, molecular beam epitaxy, pulsed laser deposition, magnetron sputtering and the like. And generating unidirectionally arranged transition metal chalcogenide crystal grains on the surface of the sapphire single crystal, and gradually growing up the crystal grains along with the reaction and splicing the crystal grains with each other to obtain the large-area transition metal chalcogenide single crystal.

Wherein, the process of preparing the transition metal chalcogenide crystal by adopting a chemical vapor deposition method comprises the following steps: placing the cut sapphire single crystal in a chemical vapor deposition chamber, adding a transition metal chalcogenide growth source, setting the reaction conditions of the growth source, and generating unidirectionally arranged transition metal chalcogenide grains on the surface of the sapphire single crystal substrate; then continuously introducing a growth source, gradually growing the crystal grains of the transition metal chalcogenide, and splicing the crystal grains to obtain large-area transition metal chalcogenide single crystals.