阅读说明：本技术 一种硫族元素化合物晶片辅助局域生长过渡金属硫族化合物的方法 (Method for locally growing transition metal chalcogenide with assistance of chalcogenide wafer ) 是由 刘开辉 左勇刚 刘灿 于 2020-04-09 设计创作，主要内容包括：本发明涉及一种硫族元素化合物晶片辅助局域生长过渡金属硫族化合物的方法,所述制备方法包括如下步骤：将预备好的衬底均匀涂一层过度金属源后反扣于硫族元素化合物晶片上,二者构建出局域空间置于管式炉中。在高温情况下,由硫族元素晶片释放的硫族元素与衬底上的过渡金属源直接发生反应在衬底上得到相应的过渡金属化合物。相比常规CVD方法,该方法完美解决了在生长过程中前驱体源扩散供应不足不均匀的问题。具有工艺简单,生长速度快,普适性强等特点,可用于制备不同种类的过渡金属硫族化合物(TMDC)材料,为二维材料的制备提供了一种新思路。(The invention relates to a method for locally growing transition metal chalcogenide by assisting a chalcogenide wafer, which comprises the following steps: and uniformly coating a layer of transition metal source on the prepared substrate, and reversely buckling the substrate on the chalcogenide crystal wafer, wherein a local space is formed by the transition metal source and the chalcogenide crystal wafer and is placed in the tube furnace. Under the condition of high temperature, the chalcogen released from the chalcogen wafer directly reacts with the transition metal source on the substrate to obtain the corresponding transition metal compound on the substrate. Compared with the conventional CVD method, the method perfectly solves the problem of insufficient and uneven diffusion supply of the precursor source in the growth process. The method has the characteristics of simple process, high growth speed, strong universality and the like, can be used for preparing different transition metal chalcogenide (TMDC) materials, and provides a new idea for the preparation of two-dimensional materials.)

1. A method for locally growing a transition metal chalcogenide on a chalcogenide wafer, the method comprising the steps of:

forming a transition metal source on a first surface of a substrate;

and (II) taking a chalcogenide compound wafer as a chalcogen element supply source, reversely buckling the prepared substrate on the wafer, putting the wafer on a high-temperature-resistant plate together to form a laminated body, and putting the laminated body in a tube furnace, wherein the laminated body sequentially comprises the following components from top to bottom: a substrate, a wafer, and a high temperature resistant plate; the first surface of the substrate is arranged opposite to the wafer, and a gap is formed between the substrate and the wafer;

introducing protective gas at normal pressure or low pressure, heating, controlling the heating rate at 5-100 deg.C/min, heating to a predetermined temperature, and maintaining the temperature for growth for less than 30 min; wherein the predetermined temperature range is 500-1000 ℃;

and (IV) after the growth is finished, closing a heating power supply, keeping the flow of the protective gas unchanged, and cooling to room temperature to obtain the transition metal chalcogenide material.

2. The method of claim 1, further comprising, before step one, the steps of: and carrying out pretreatment on the substrate, wherein the pretreatment comprises plasma treatment, KOH solution treatment or piranha solution treatment.

3. The method of claim 1, wherein the substrate comprises SiO₂Substrate, sapphire, fused silica or mica sheet.

4. The method according to claim 1, wherein step one comprises in particular the steps of: uniformly spin-coating a transition metal source on the prepared substrate by a spin coating method, and then placing the substrate on a heating table at 60-100 ℃ for dehumidification and drying; or, the step one specifically comprises the following steps: and uniformly forming the transition metal on the prepared substrate by adopting a spraying, sputtering or thermal evaporation method.

5. The method of claim 1, wherein the transition metal source comprises a liquid source or a solid source;

preferably, the liquid source comprises: sodium molybdate, sodium tungstate, or ammonium molybdate; the solid source includes: a transition metal target;

preferably, the transition metal target comprises molybdenum oxide, or tungsten oxide.

6. The method of claim 1, wherein the wafer comprises a sulfide, selenide, or telluride;

preferably, the wafer comprises ZnS, ZnSe or TeO₂。

7. The method of claim 1, wherein the gap height is between 10 μ ι η and 5 mm.

8. The method of claim 1, wherein the raising the temperature at the low pressure in step three comprises: vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to be 50-300Pa, and heating to a preset temperature;

preferably, the protective gas also simultaneously acts as a carrier gas;

preferably, the protective gas comprises Ar or N₂。

9. The method of claim 1, wherein the high temperature resistant plate comprises a quartz plate.

10. The method according to claim 1 or 2, characterized in that said transition metal chalcogenide comprises MoS₂、MoSe₂、MoTe₂、WS₂、WSe₂Or WTE₂Or a heterojunction MoS₂-WS₂、MoSe₂-WSe₂Or MoTe₂-WTe₂。

Technical Field

The invention belongs to the technical field of two-dimensional material growth, and particularly relates to a method for quickly, simply and conveniently preparing a transition metal chalcogenide.

Background

With the rise of graphene hot tide in recent years, two-dimensional materials are gradually concerned by researchers. In fact, two-dimensional materials have been widely studied, in addition to graphene, which is now well known, transition metal chalcogenides (TMDC) having semiconductor characteristics and hexagonal boron nitride (h-BN) having insulator characteristics. Compared with a graphene zero-band-gap material, TMDC is a semiconductor two-dimensional material with a band gap width, and the band gap width changes along with the thickness of the material, so that the TMDC has unique electronic and photoelectric characteristics, such as strong light absorption, strong exciton effect, high electron mobility, piezoelectric characteristics and the like, is considered as the most ideal material for replacing a silicon-based semiconductor in the post-molar era, and can be widely applied to a plurality of intelligent living facilities such as ultrashort wave transistors, hypersensitive devices, piezoelectric sensors and the like in the future. In order to meet the above requirements, the preparation of high quality two-dimensional TMDC materials is the largest short plate that currently limits its applications. Therefore, it is urgently needed to develop a reliable and convenient preparation method of TMDC with high quality.

The currently conventional methods for preparing TMDC are mainly Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). The CVD method is mainly to prepare TMDC material on the prepared substrate by high temperature reaction of transition metal oxide or chloride and volatile sulfur. However, due to the limitation of precursor mass transfer and the influence of low sublimation point of a sulfur source in the CVD process, a large number of sulfur defect vacancies exist in the prepared TMDC sample on one hand, and the quality of the sample is seriously influenced; on the other hand, the influence of the precursor concentration gradient causes the sample to be uneven. Even in the process of preparing the two-dimensional telluride material, Te vapor reacts with the silicon substrate to generate a byproduct, which is not beneficial to the growth of the sample. How to avoid the influence of precursor mass transfer, ensure the sufficient reaction of the precursor, and accurately prepare a high-quality TMDC sample according to the stoichiometric coefficient ratio of the chalcogen and the transition metal in the TMDC sample is a technical problem to be solved urgently.

Disclosure of Invention

The present invention is directed to a method for locally growing a transition metal chalcogenide using a chalcogenide, the method comprising the steps of:

forming a transition metal source on a first surface of a substrate;

and (II) taking a chalcogenide compound wafer as a chalcogen element supply source, reversely buckling the prepared substrate on the wafer, putting the wafer on a high-temperature-resistant plate together to form a laminated body, and putting the laminated body in a tube furnace, wherein the laminated body sequentially comprises the following components from top to bottom: a substrate, a wafer, and a high temperature resistant plate; the first surface of the substrate is arranged opposite to the wafer, and a gap is formed between the substrate and the wafer;

introducing protective gas at normal pressure or low pressure, heating, controlling the heating rate at 5-100 deg.C/min, heating to a predetermined temperature, and maintaining the temperature for growth for less than 30 min; wherein the predetermined temperature range is 500-1000 ℃;

and (IV) after the growth is finished, closing a heating power supply, keeping the flow of the protective gas unchanged, and cooling to room temperature to obtain the transition metal chalcogenide material.

Preferably, the following steps are further included before the step one: and carrying out pretreatment on the substrate, wherein the pretreatment comprises plasma treatment, KOH solution treatment or piranha solution treatment.

Preferably, the substrate comprises SiO₂A substrate, sapphire, fused silica, or mica sheet substrate.

Preferably, the step one specifically comprises the following steps: uniformly spin-coating a transition metal source on the prepared substrate by a spin coating method, and then placing the substrate on a heating table at 60-100 ℃ for dehumidification and drying; or, the step one specifically comprises the following steps: and uniformly forming the transition metal on the prepared substrate by adopting a spraying, sputtering or thermal evaporation method.

Preferably, the transition metal source comprises a liquid source or a solid source;

preferably, the liquid source comprises: sodium molybdate, sodium tungstate, or ammonium molybdate; the solid source includes: a transition metal target;

preferably, the transition metal target comprises molybdenum oxide, or tungsten oxide.

Preferably, the wafer comprises a sulfide, selenide or telluride;

preferably, the wafer comprises ZnS, ZnSe or TeO₂。

Preferably, the gap height is 5mm or less;

preferably, the gap height is 10 μm to 5 mm.

Preferably, the raising the temperature at a low pressure in the third step comprises: vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to be 50-300Pa, and heating to a preset temperature;

preferably, the protective gas also simultaneously acts as a carrier gas;

preferably, the protective gas comprises Ar or N₂。

Preferably, the high temperature resistant plate comprises a quartz plate.

Preferably, the transition metal chalcogenide comprises MoS₂、MoSe₂、MoTe₂、WS₂、WSe₂Or WTE₂Or a heterojunction MoS₂-WS₂、MoSe₂-WSe₂Or MoTe₂-WTe₂。

The invention mainly adopts the chalcogenide crystal plate as the chalcogenide supply source, and forms a local space with the substrate containing the transition metal source, forms a high-concentration perfect stoichiometric coefficient element proportion in the space, and abandons the long-distance diffusion limitation of the growth source in the conventional CVD, thereby quickly preparing the high-quality transition metal chalcogenide sample. Not only the transition metal chalcogenide material with controllable layer number and high quality is obtained, but also a plurality of transition metal chalcogenide materials can be prepared. The invention provides a universal new way for preparing the transition metal chalcogenide material, and easily realizes the preparation of different transition metal chalcogenide materials.

The invention has the advantages that:

1. in contrast to conventional CVD methods, sulfide crystals are used in the present inventionThe tablet replaces chalcogen powder, the supply temperature of chalcogen is raised critically, and the problem of insufficient chalcogen in the growth process is solved; wherein the sulfide wafer may be single crystal or polycrystalline. The wafer can be purchased directly or prepared by crystal pulling method, and the size of the wafer is cut and customized according to the experimental requirement, and is generally 2 multiplied by 2cm²The thickness of the square wafer is 0-2 mm.

2. The local growth mode concentrates growth sources in a micro space, and ensures the full reaction of precursors through experimental condition optimization.

3. The prepared sample is prevented from being uneven due to the precursor concentration gradient caused by the mass transfer process;

4. compared with the conventional method, the growth source does not need a long-distance mass transfer process, and directly reacts in a limited space, so that the overall preparation time is shortened.

5. As a general method, various different types of transition metal chalcogenide materials can be prepared.

Drawings

Fig. 1 is a schematic view of the process of growing a transition metal chalcogenide material according to the present invention.

Figure 2 is an optical topography of a molybdenum disulfide sample of example 1 of the present invention.

FIG. 3 is a Raman (left) and fluorescence (right) spectra of a sample of molybdenum disulfide according to example 1 of the present invention.

Fig. 4 is an optical topography of a molybdenum diselenide sample of example 2 of the present invention.

Fig. 5 is a raman (left) and fluorescence (right) spectra of a sample of molybdenum diselenide of example 2 of the present invention.

FIG. 6 is MoS of example 3 of the present invention₂-WS₂Optical topography of the heterojunction sample.

FIG. 7 is the MoS of example 3 of the present invention₂-WS₂Heterojunction sample fluorescence (PL) spectrum (left) and PLmapping (right).

Detailed Description

The present invention will be described in further detail with reference to specific examples.

The invention provides a method for locally growing transition metal chalcogenide by a chalcogenide wafer, which comprises the following steps:

forming a transition metal source on a first surface of a substrate, the substrate further comprising a second surface opposite the first surface;

and (II) taking a chalcogenide compound wafer as a chalcogen element supply source, reversely buckling the prepared substrate on the wafer, putting the wafer on a high-temperature-resistant plate together to form a laminated body, and putting the laminated body in a tube furnace, wherein the laminated body sequentially comprises the following components from top to bottom: a substrate, a wafer, and a high temperature resistant plate; the first surface of the substrate is arranged opposite to the wafer, the second surface is arranged far away from the wafer relative to the first surface, and a gap is formed between the substrate and the wafer;

introducing protective gas at normal pressure or low pressure, heating, controlling the heating rate at 5-100 deg.C/min, heating to a predetermined temperature, and maintaining the temperature for growth for less than 30 min; wherein the predetermined temperature range is 500-1000 ℃;

and (IV) after the growth is finished, closing a heating power supply, keeping the flow of the protective gas unchanged, and cooling to room temperature to obtain the transition metal chalcogenide material.

The wafer may be a single wafer or a multi-wafer of chalcogenide, which may be purchased directly or prepared by crystal pulling, and may have various shapes such as circular, square, polygonal, etc., and may have radial dimensions of 1-10cm wide, 1-10cm long, and a thickness of about 2mm or less. In one specific embodiment, the wafer is 2X 2cm²The square wafer of (2) may have a thickness of 2mm or less, specifically, 2 mm.

In a specific embodiment, the raising the temperature at the low pressure in the third step comprises: and vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to be 50-300Pa, and heating to a preset temperature.

In a specific embodiment, before the step one, the following steps are further included: and carrying out pretreatment on the substrate, wherein the pretreatment comprises plasma treatment, KOH solution treatment or piranha solution treatment.

In a specific embodiment, the substrate comprises SiO₂a/Si, sapphire, fused silica, or mica sheet substrate.

In a specific embodiment, the step one specifically includes the following steps: uniformly spin-coating the transition metal precursor on the prepared substrate by a spin coating method, and then placing the substrate on a heating table at 60-100 ℃ for dehumidification and drying. Alternatively, the first step may be to uniformly form the transition metal on the prepared substrate by using a spraying, sputtering or thermal evaporation method.

In a specific embodiment, the transition metal source used includes a liquid source or a solid source;

in a particular embodiment, the liquid source comprises: sodium molybdate, sodium tungstate, or ammonium molybdate; the solid source includes: a transition metal target. The transition metal target material is molybdenum oxide or tungsten oxide.

In a particular embodiment, the wafer comprises a sulfide, selenide or telluride.

In a specific embodiment, the protective gas also serves simultaneously as a carrier gas; the protective gas comprises Ar or N₂。

In one embodiment, the substrate is flipped over the chalcogenide wafer with a localized space formed between the two gaps. Preferably the gap distance is in the order of mm.

In a specific embodiment, an atmospheric growth mode may also be selected.

In a specific embodiment, the high temperature resistant plate comprises a quartz plate.

In a specific embodiment, the chalcogenide wafer comprises ZnS, ZnSe or TeO₂。

In a specific embodiment, the transition metal chalcogenide comprises MoS₂、MoSe₂、MoTe₂、WS₂、WSe₂Or WTE₂Or a heterojunction MoS₂-WS₂、MoSe₂-WSe₂Or MoTe₂-WTe₂。

A gap is formed between the substrate and the wafer by adopting a spacer with a known thickness, and the height of the gap is less than 5 mm; preferably, the gap height is 10 μm to 5 mm. In a specific embodiment, the gap is 1 mm. For example, 3 to 10 spacers having the same height may be placed between the substrate and the wafer and disposed along the circumferential direction of the substrate or the wafer so as not to adversely affect the growth of the transition metal chalcogenide.

The starting material may be obtained from publicly available commercial sources, such as powdered Na₂MoO₄、K₂MoO₄、Na₂WO₄、K₂WO₄Available from Alfa Aesar. Substrates such as silicon oxide, fused silica, and aluminum oxide are commercially available from mixcrystal corporation. Chalcogenide wafers are available from Toho New materials technology, Inc. and have dimensions of less than 2mm in thickness and 2X 2cm in area²Square wafers of (4); the sulfide wafer may be single crystal or polycrystalline. The wafer can also be prepared by adopting a crystal pulling method, and the size is cut and customized according to the experiment requirement. The wafer is generally 2X 2cm²The square wafer of (2) has a thickness of 2mm or less.

The invention mainly adopts the chalcogenide crystal plate as the chalcogenide supply source, and forms a local space with the substrate containing the transition metal source, forms a high-concentration perfect stoichiometric coefficient element proportion in the space, and abandons the long-distance diffusion limitation of the growth source in the conventional CVD, thereby quickly preparing the high-quality transition metal chalcogenide sample. Not only the transition metal chalcogenide material with controllable layer number and high quality is obtained, but also a plurality of transition metal chalcogenide materials can be prepared. The invention provides a universal new way for preparing the transition metal chalcogenide material, and easily realizes the preparation of different transition metal chalcogenide materials.

The invention has the advantages that:

1. sulfide wafers replace chalcogen powders, critical compared to conventional CVD processesThe supply temperature of the chalcogen is increased, and the problem of insufficient S in the growth process is solved; wherein the sulfide wafer may be single crystal or polycrystalline. The wafer is prepared by a crystal pulling method, the size of the wafer is cut and customized according to the experimental requirement, and 2 x 2cm is adopted²The square wafer of (2) has a thickness of 2mm or less.

2. The local growth mode concentrates growth sources in a micro space, and ensures the full reaction of precursors through experimental condition optimization.

3. The prepared sample is prevented from being uneven due to the precursor concentration gradient caused by the mass transfer process;

4. compared with the conventional method, the growth source does not need a long-distance mass transfer process, and directly reacts in a limited space, so that the overall preparation time is shortened.

5. As a general method, various different types of transition metal chalcogenide materials can be prepared.

FIG. 1 is a schematic view of a process for growing a transition metal chalcogenide material according to the present invention, in FIG. 1, a substrate 101 is first pre-treated; then, the substrate 101 is placed on a spin-coating platform 102, and a chalcogen element supply source is formed on the first surface of the substrate 101 in a spin-coating mode; the substrate 101 is then flipped over onto the wafer 103, wherein the first surface of the substrate 101 is disposed opposite the wafer 103. Finally, the growth of the transition metal chalcogenide material is carried out at atmospheric or low pressure.

Example 1

In the schematic diagram of the apparatus shown in fig. 1, the specific steps for preparing molybdenum disulfide by using silicon dioxide as a substrate are as follows:

(one) applying oxygen plasma to SiO₂The substrate is pretreated to improve the hydrophilicity of the surface. Then Na is added by a spin coating method₂MoO₄The solution is evenly coated on SiO₂And (3) placing the substrate on the first surface of the substrate in a 60-100 ℃ heating table for dehumidifying and drying.

And (II) adopting a ZnS wafer as a chalcogen element supply source. Spin-coating uniform SiO₂The substrate is placed on the wafer in a reverse buckling manner, placed on a quartz plate together, and placed in a tube furnace, wherein the substrate is rotatedCoated with Na₂MoO₄Is disposed opposite the wafer. The substrate and wafer are separated by a spacer of known thickness to form a gap, the gap height being 1 mm.

And (III) vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to 150Pa, controlling the heating rate at 15 ℃/min, heating to 750 ℃ and then carrying out heat preservation growth for 5 min.

(IV) after the growth is finished, turning off the heating power supply, keeping the Ar flow unchanged, and cooling to room temperature to obtain SiO₂Single layer MoS on substrate₂Samples, as shown in FIG. 2. Wherein, the left picture of FIG. 2 is SiO₂Single layer MoS on substrate₂The topography of the sample can be seen in SiO₂Regular triangular molybdenum disulfide crystal domains on the substrate. FIG. 3 is a Raman (left) and fluorescence (right) spectra of a sample of molybdenum disulfide according to example 1 of the present invention.

Example 2

The specific steps for preparing molybdenum diselenide by using silicon dioxide as a substrate are as follows:

(one) applying oxygen plasma to SiO₂The substrate is pretreated to improve the hydrophilicity of the surface. Then Na was added by spin coating₂MoO₄The solution is evenly coated on SiO₂And (3) placing the substrate on the first surface of the substrate in a 60-100 ℃ heating table for dehumidifying and drying.

And (II) ZnTe wafer is used as the chalcogen element supply source. Spin-coating uniform SiO₂The substrate was placed upside down on a wafer and placed together on a quartz plate in a tube furnace, in which Na was spin-coated₂MoO₄Is disposed opposite the wafer. The substrate and wafer are separated by a spacer of known thickness to form a gap, the gap having a height of 2 mm.

And (III) vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to 150Pa, controlling the heating rate at 15 ℃/min, heating to the preset temperature of 800 ℃, and then carrying out heat preservation growth for 10 min.

(IV) after the growth is finished, turning off the heating power supply, keeping the Ar flow constant, and coolingCooling to room temperature to obtain SiO₂Single layer of MoSe on a substrate₂Sample, as shown in fig. 4. Wherein, the left picture of FIG. 4 is SiO₂Single layer of MoSe on a substrate₂The topography of the sample can be seen in SiO₂Regular triangle molybdenum diselenide crystal domains on the substrate. Fig. 5 is a raman (left) and fluorescence (right) spectra of a sample of molybdenum diselenide of example 2 of the present invention.

Example 3

MoS preparation using fused silica as substrate₂-WS₂The specific steps of the heterojunction are as follows:

firstly, preprocessing the fused quartz substrate by adopting oxygen plasma to improve the hydrophilicity of the surface. Then Na was added by spin coating₂MoO₄And Na₂WO₄The mixed solution (mass ratio is 1: 3) is uniformly coated on the first surface of the fused quartz substrate, and is placed on a heating table at 60-100 ℃ for dehumidification and drying.

And (II) adopting a ZnS wafer as a chalcogen element supply source. And reversely buckling the uniformly spin-coated fused quartz substrate, placing the substrate on a wafer, placing the substrate on a quartz plate, and placing the substrate in a tube furnace, wherein the first surface of the substrate is opposite to the wafer. . The substrate and wafer are separated by a spacer of known thickness to form a gap, the gap height being 1 mm.

And (III) vacuumizing the tube furnace until the air pressure in the tube furnace is lower than 0.1Pa, introducing protective gas, maintaining the pressure in the tube to 150Pa, controlling the heating rate at 15 ℃/min, heating to a preset temperature of 850 ℃, and then carrying out heat preservation and growth for 10 min.

(IV) after the growth is finished, turning off the heating power supply, keeping the Ar flow unchanged, and cooling to room temperature to obtain SiO₂Substrate out-of-plane heterojunction MoS₂-WS₂Sample, as shown in fig. 6. Wherein FIG. 6 is SiO₂Mass-bonded MoS on substrate₂-WS₂Topography of the sample. FIG. 7 shows a heterojunction MoS according to example 3 of the present invention₂-WS₂Sample and fluorescence spectra (left) and PLmapping (right).