阅读说明：本技术 一种大晶畴尺寸ws2单晶的生长方法 (Large domain size WS2Method for growing single crystal ) 是由 兰飞飞 王再恩 董增印 张嵩 王健 张胜男 李轶男 霍晓青 于 2020-05-29 设计创作，主要内容包括：本发明公开了一种大晶畴尺寸WS<Sub>2</Sub>单晶的生长方法。该方法采用半封闭方式步骤是：将WO<Sub>3</Sub>粉末置于石英舟中,将衬底放在石英舟顶部,将石英舟放入半封闭石英管中；将石英管放入系统中进行抽真空,当压力为0mbar时,通入Ar气,压力保持在10-20mbar；对系统进行升温,将温度升至900-1000℃,达到设定温度后对硫粉进行加热,温度为190-250℃；达到设定温度后通入硫蒸汽进行WS<Sub>2</Sub>单晶的生长,生长时间为20-50min。采用半封闭方式提高成核以及生长过程中钨源的过饱和度,使得成核生长过程中衬底表面钨源供应充足,保证生长的顺利进行,能够显著增大WS<Sub>2</Sub>单晶的晶畴尺寸,利于大晶畴尺寸WS<Sub>2</Sub>单晶的生长。(The invention discloses a large domain size WS 2 A method for growing a single crystal. The method adopts a semi-closed mode and comprises the following steps: mixing WO 3 Putting the powder into a quartz boat, putting the substrate on the top of the quartz boat, and putting the quartz boat into a semi-closed quartz tube; putting the quartz tube into a system, vacuumizing, introducing Ar gas when the pressure is 0mbar, and keeping the pressure at 10-20 mbar; heating the system to 900-; after reaching the set temperature, introducing sulfur steam for WS 2 And (3) growing the single crystal for 20-50 min. The supersaturation degree of the tungsten source in the nucleation and growth processes is improved by adopting a semi-closed mode, so that the tungsten source supply on the surface of the substrate in the nucleation and growth processes is sufficient, the smooth growth is ensured, and the WS can be remarkably increased 2 The size of the domains of the single crystal is favorable for the size WS of large domains 2 And (4) growing a single crystal.)

1. Large domain size WS₂A method for growing a single crystal, characterized in that in WS₂The supersaturation degree of the W source is improved in a semi-closed mode in the process of single crystal growth, and then WS is realized₂The crystal domain size is enlarged, and the crystal growth process is completed according to the following steps:

firstly, putting a certain amount of sulfur powder into a material bottle by using an electronic balance;

in the second step, using an electronic balanceA certain amount of WO₃Placing the powder in a quartz boat, and placing the substrate growth surface downwards on the surface of the quartz boat;

third, the substrate is placed on the substrate and WO₃The quartz boat of the powder is arranged in a semi-closed quartz tube with an opening at one end;

fourthly, placing the semi-closed quartz tube into a CVD growth system; vacuumizing the CVD growth system, and introducing Ar gas for purging when the pressure in the system is 0mbar, wherein the flow rate of the Ar gas is 500 sccm;

fifthly, reducing the flow rate of Ar to 100sccm-150sccm, and keeping the pressure in the system at 10-20 mbar;

sixthly, heating the system, namely heating the system to 900-1000 ℃, starting to heat the sulfur powder after the system reaches the growth temperature, and controlling the heating temperature to 190-250 ℃;

seventhly, after the temperature of the sulfur powder reaches the set temperature, introducing sulfur steam into the system, and starting WS₂Growing the single crystal for 20-50 min;

and eighthly, finishing the growth, cooling and sampling.

Technical Field

The invention relates to a method for preparing WS by adopting a CVD method₂Single crystal process, especially large domain size WS₂A method for growing a single crystal.

Background

Two-dimensional WS₂Is a typical representative of transition metal sulfides, is a typical two-dimensional layered material, a single layer of WS₂The mobility of the direct band gap semiconductor material exceeds 1000cm²V.s, which is much higher than the mobility of silicon material with the same thickness; WS₂The surface has no dangling bond, so that good stability can be maintained in a complex environment; WS₂The base field effect transistor has ultra-low crystalline state power consumption, and the application of the base field effect transistor can remarkably reduce the system power consumption. Furthermore, WS₂Has excellent optical performance and good mechanical flexibility. For this purpose, WS₂Has potential application prospect in the fields of micro-electronics, flexible photoelectrons and the like.

WS has been obtained by researchers at present on wafer level using CVD₂A single-layer continuous film is obtained by combining and growing single crystals which are spontaneously nucleated at different positions, the spontaneously nucleated single crystals have different scenes, so that a large number of grain boundaries exist in the continuous film, the grain boundaries are defect gathering positions, the quality of the film is seriously reduced, and WS is seriously reduced₂The mobility of the material. Therefore, large domain size WS is achieved₂Study of growth of Single Crystal is WS₂The problem that must be solved in the research process. WS currently prepared by CVD₂The domain size is only several tens of micrometers, and it is difficult to obtain WS having a large domain size₂And (3) single crystal.

WS by current CVD method₂WO is mainly adopted in the process of single crystal growth₃As W source, high-purity S powder as sulfur sourceThe long-term heated S vapor reaches WO along with the transport of the carrier gas₃Source region, and WO₃Carrying out the reaction to obtain WO_3-XThe compound of the degraded W source is deposited on the surface of the substrate, and with the continuous supply of S vapor, the oxide of the W source is completely vulcanized to obtain WS₂A film material. In WS₂The main difficulty in the process of single crystal growth is that the supersaturation degree of the W source is too low in the nucleation and growth processes, and the required supersaturation degree of the W source cannot be obtained on the substrate surface due to the too low supersaturation degree of the W source, so that the size of a crystal domain is difficult to expand. The main reason for the over-low supersaturation of the W source is WO₃Has a melting point as high as 1473 ℃ and the temperature of the conventional CVD growth system is 1200 ℃, so that the over-saturation of the W source in the growth process is difficult to meet the large-domain-size single crystal WS₂The need for growth. How to adopt effective measures to improve the supersaturation degree of the W source and realize the large domain size WS₂Stable growth of single crystals, is WS₂The difficult problem to be solved urgently in the research process.

Disclosure of Invention

The invention aims to solve the problem of growing WS by the existing CVD method₂The problem of undersize crystal domain in the single crystal process, in particular to provide a large crystal domain size WS₂Method for growing single crystal to achieve increase of WS₂Single domain size, increasing WS₂Quality of the single crystal.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: large domain size WS₂A method for growing a single crystal, characterized in that in WS₂The supersaturation degree of the W source is improved in a semi-closed mode in the process of single crystal growth, and then WS is realized₂The crystal domain size is enlarged, and the crystal growth process is completed according to the following steps:

firstly, a certain amount of sulfur powder is placed in a material bottle by using an electronic balance.

Second, a quantity of WO is applied using an electronic balance₃The powder was placed in a quartz boat with the substrate growth side down on the quartz boat surface.

Third, the substrate is placed on the substrate and WO₃The quartz boat of the powder is arranged in a semi-closed stone with an opening at one endIn the quartz tube.

Fourthly, placing the semi-closed quartz tube into a CVD growth system; and (3) vacuumizing the CVD growth system, and introducing Ar gas for purging when the pressure in the system is 0mbar, wherein the flow of the Ar gas is 500 sccm.

And fifthly, reducing the flow rate of Ar gas to 100sccm-150sccm, and keeping the pressure in the system at 10mbar-20 mbar.

And sixthly, heating the system, namely heating the system to 900-1000 ℃, starting to heat the sulfur powder after the system reaches the growth temperature, and controlling the heating temperature to 190-250 ℃.

Seventhly, after the temperature of the sulfur powder reaches the set temperature, introducing sulfur steam into the system, and starting WS₂And (3) growing the single crystal for 20-50 min.

And eighthly, finishing the growth, cooling and sampling.

The invention prepares the large domain size WS₂Principle of single crystal: WO3 was placed directly with the substrate in the growth system during conventional WS2 single crystal growth by introducing the semi-enclosed apparatus before growth began. Compared with the traditional method, under the condition that the evaporation amount of WO3 in unit time is the same, the semi-closed device introduced in the invention can gather the evaporated WO3 in a smaller space, improve the vapor pressure of WO3, further effectively improve the supersaturation degree of a W source in the growth process of WS2, further realize the enlargement of the size of the single crystal, and the size of the WS2 single crystal can be enlarged to 400 microns by adopting the method, while the size of the WS2 single crystal obtained by the conventional growth method is usually only tens of microns.

The invention has the beneficial effects that: large domain size WS by semi-closed mode₂Growth of a single crystal, effecting WS₂The supersaturation degree of the W source is improved in the nucleation and growth processes, thereby realizing WS₂And the supersaturation degree of the W source is required in the growth process, so that the expansion of the size of the crystal domain is realized. The application of the method can realize large domain size WS₂Controlled growth of single crystals.

Drawings

FIG. 1 is a schematic view of a semi-closed growth apparatus according to the present invention.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings: