CN117822121A - Method for growing transition metal sulfur compound single crystal wafer - Google Patents

Method for growing transition metal sulfur compound single crystal wafer Download PDF

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Publication number
CN117822121A
CN117822121A CN202310255352.0A CN202310255352A CN117822121A CN 117822121 A CN117822121 A CN 117822121A CN 202310255352 A CN202310255352 A CN 202310255352A CN 117822121 A CN117822121 A CN 117822121A
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transition metal
substrate
single crystal
sulfur compound
crystal wafer
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张艳锋
杨鹏飞
胡静怡
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Peking University
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Peking University
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract

The invention discloses a growth method of a transition metal sulfide single crystal wafer, which comprises the following steps: 1) Annealing the single crystal sapphire; 2) Taking the annealed sapphire wafer as a substrate, placing a transition metal foil parallel to the substrate, and placing a porous barrier layer between the foil and the substrate in parallel; 3) Placing elemental sulfur upstream of the gas stream of the substrate; 4) Introducing mixed gas into a low-pressure chemical vapor deposition system, respectively heating a substrate and elemental sulfur to a set temperature after the gas flow is stable, and then keeping the temperature constant to prepare a single-orientation transition metal sulfur compound triangular domain on the substrate; 5) And the constant temperature time is prolonged, so that the triangle domains of the single-orientation transition metal sulfur compound are spliced into the transition metal sulfur compound single crystal wafer in a seamless manner. The invention realizes the preparation of the transition metal sulfide single crystal wafer with high repeatability and high quality.

Description

Method for growing transition metal sulfur compound single crystal wafer
Technical Field
The invention belongs to the field of monocrystalline wafer materials, and particularly relates to a method for growing a transition metal sulfur compound monocrystalline wafer.
Background
Two-dimensional semiconducting transition metal chalcogenides (2D TMDCs) are one of the important candidate materials for continuation of moore's law by virtue of their atomic scale thickness, excellent optoelectronic properties, and good chemical stability. The preparation of 2D TMDCs wafers is a key premise for achieving high quality two-dimensional electronic device construction and integration. Chemical Vapor Deposition (CVD) is the most promising method for the preparation of large-area, high-quality two-dimensional materials. During CVD growth, the substrate surface often has hundreds or thousands of 2D TMDCs domains, and inter-domain bonding often creates grain boundaries, so the resulting TMDCs films are often polycrystalline. In terms of electrical performance, the presence of charge defects at grain boundaries causes a large amount of charge scattering, which hinders the improvement of transistor performance. In addition, there are a large number of defects at the grain boundaries, which also have a significant influence on the optical properties of the material, such as a significant decrease in Second Harmonic (SHG) intensity and fluorescence intensity at the grain boundaries, and the like, which prevent its application in the electron/photoelectron field. Therefore, in order to pursue the excellent crystal quality and excellent optical and electrical properties, the controllable preparation of 2D TMDCs single crystal wafers is of great importance.
The TMDCs monocrystal film prepared by the CVD method mainly has two strategies of mononuclear growth and polynuclear epitaxial growth, wherein the former strategy needs to control only one nucleation site on a substrate, and single nuclei continuously grow to form monocrystals. However, this method requires very high control of the source and generally requires long growth times. The multi-core epitaxial growth method is to realize single orientation nucleation on a single crystal substrate and form single crystals by seamless splicing of the same orientation domains. Compared with a single-core growth method, the multi-core epitaxial growth method allows a plurality of nucleation sites on a substrate, and the time required for preparing film samples with the same size is shorter, so that the amplification of the size of the samples is facilitated. However, the TMDCs film obtained by the multi-core epitaxial growth route still has the problems of difficult size enlargement, small domain area size and the like. Therefore, it is very important to develop a method for preparing a transition metal sulfur compound single crystal wafer having high reproducibility, low nucleation density and scalable size.
Disclosure of Invention
The invention aims to provide a low-pressure chemical vapor deposition method, which takes monocrystalline sapphire as a substrate to prepare a single-orientation transition metal sulfur compound nanosheet so as to prolong the growth time and obtain a two-dimensional transition metal sulfur compound monocrystalline wafer.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention provides a method for growing a transition metal sulfur compound single crystal wafer, which comprises the following steps:
1) Annealing the single crystal sapphire at a high temperature for a long time;
2) Taking the annealed sapphire wafer as a substrate, folding a transition metal foil into a bridge shape, placing the bridge shape parallel to the substrate, and placing a porous barrier layer (such as carbon cloth) between the foil and the substrate in parallel;
3) Placing elemental sulfur upstream of the gas stream of the substrate;
4) Introducing mixed gas (such as argon and oxygen) into the low-pressure chemical vapor deposition system, respectively heating the substrate and elemental sulfur to a set temperature after the gas flow is stable, and then keeping the temperature for a plurality of minutes to prepare a single-orientation transition metal sulfur compound triangular domain on the substrate;
5) And the constant temperature time is prolonged, so that the triangular domains of the single-orientation transition metal sulfur compound are spliced into the single-crystal thin film of the transition metal sulfur compound single crystal wafer size in a seamless manner.
Preferably, in step 1), the single crystal sapphire substrate is annealed as follows: heating to 1100-1500 deg.C under atmospheric condition, maintaining the temperature for 5-10 hr, and naturally cooling to room temperature.
Preferably, in step 2), the transition metal foil has a thickness of 20-30 μm, and the transition metal foil comprises a molybdenum foil or a tungsten foil.
Preferably, in the step 2), the transition metal foil is placed parallel to the sapphire substrate, and the distance between the foil and the substrate is 0.5-2cm.
Preferably, in step 2), a porous barrier layer (such as carbon cloth) is disposed between the substrate and the transition metal foil, and the barrier layer is disposed proximate to the substrate.
Preferably, in step 3), the distance between the substrate and the elemental sulphur (sulphur powder) is between 10 and 20cm.
Preferably, in the step 3), the mass of the elemental sulfur is 10-15 g.
Preferably, in the step 4), the elemental sulfur and the substrate are heated respectively, the elemental sulfur is heated to 95-120 ℃, the heating temperature of the substrate is consistent with that of the transition metal foil and is 850-1000 ℃, and the constant temperature is kept for 5-8min.
Preferably, in the step 4), the low pressure condition is 18-180Pa, the mixed gas comprises argon and oxygen, the flow of the argon is 50-100 sccm, and the flow of the oxygen is 1-5 sccm, wherein sccm is a volume flow unit, namely standard milliliters per minute.
Preferably, in step 5), the constant temperature time is 8-20min.
The low pressure chemical vapor deposition system is a conventional technical means in the field.
The invention takes the monocrystalline sapphire as a substrate, ensures the uniformity of wafer size nucleation by utilizing a face-to-face transition metal source supply mode, introduces a porous barrier layer to effectively reduce nucleation density, realizes the growth of single-orientation transition metal sulfur compound triangle nano-sheets and the preparation of monocrystalline wafers by controlling the proportion of transition metal sources and sulfur sources, and is a comprehensive preparation strategy for realizing the transition metal sulfur compound monocrystalline wafers.
Compared with the prior art, the invention has the advantages that:
the transition metal foil used in the invention is used as a metal precursor, and is placed parallel to the substrate, so that the uniform supply of the precursor and the preparation of the transition metal sulfur compound sample with uniform wafer size are effectively ensured. The method has expandability and is expected to realize the amplification of the wafer size.
The barrier layer auxiliary strategy adopted by the invention can effectively regulate and control the deposition rate and the supply concentration of the precursor, further regulate and control the nucleation density and the domain area size, and realize the preparation of the transition metal sulfide single crystal wafer with high repeatability and high quality.
Drawings
FIG. 1 is an atomic force microscope image of a sapphire single crystal substrate obtained after annealing according to example 1;
FIG. 2 is an optical microscope photograph of a single oriented molybdenum disulfide triangular domain prepared by a chemical vapor deposition method corresponding to example 1;
FIG. 3 is a Raman spectrum of the molybdenum disulfide triangular domains and the sapphire substrate prepared in example 1;
FIG. 4 is a photograph of a 2 inch molybdenum disulfide single crystal film prepared in example 2;
FIG. 5 is a surface scan of the second harmonic generation of the molybdenum disulfide single crystal film prepared in example 2;
Detailed Description
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
The invention provides a method for growing a transition metal sulfur compound single crystal wafer, which comprises the following steps:
1) Heating the monocrystalline sapphire to 1100-1500 ℃ under the atmosphere, keeping the temperature for 5-10 hours, and naturally cooling to room temperature. Through the annealing process, an atomically flat surface and an oriented step are obtained;
2) And taking the annealed sapphire wafer as a substrate, and placing the transition metal foil parallel to the substrate at a spacing distance of 0.5-2cm. A porous barrier layer is arranged in parallel between the foil and the substrate, and the barrier layer is closely attached to the substrate;
3) Placing elemental sulfur on the upstream of the air flow of the substrate, wherein the distance between the substrate and sulfur powder is 10-20cm;
4) The connecting pipeline is used for introducing argon and oxygen into the low-pressure chemical vapor deposition system, and the pressure is 18-180Pa;
5) Heating the elemental sulfur and the substrate respectively, heating sulfur powder to 95-120 ℃, heating the substrate and the transition metal foil to 850-1000 ℃ for 5-8min, and preparing a single-orientation transition metal sulfur compound triangular domain on the substrate;
6) And the constant temperature time is prolonged, and the triangular domains of the single-orientation transition metal sulfur compound are spliced into the wafer-sized single crystal film in a seamless manner.
According to a preferred embodiment of the present invention, the method for preparing a single-layer molybdenum disulfide single-crystal wafer on a sapphire single-crystal substrate provided by the present invention comprises the following steps:
1) Heating the purchased sapphire single crystal substrate with the c-deviation a surface of 1 degree to 1200 ℃ under the atmosphere, keeping the temperature for 5 hours, and naturally cooling to room temperature;
2) Taking annealed sapphire as a substrate, and placing the substrate in a high-temperature tubular reaction furnace; folding a molybdenum foil with the thickness of 25 mu m into a bridge shape, and placing the molybdenum foil in parallel above a sapphire substrate, wherein the height of the molybdenum foil is 1 cm; covering a commercial carbon cloth with the size equivalent to that of the substrate on the substrate;
3) Sulfur 10g S powder is placed at the position of 10cm above the gas flow of the substrate, and 100sccm of high-purity argon and 1sccm of oxygen are introduced into the reaction cavity;
4) And starting a temperature-raising program to heat the reaction cavity, wherein the final temperatures of the elemental sulfur and the molybdenum foil (substrate) are 95-120 ℃ and 850-1000 ℃ respectively, the temperature-raising time is 40-50 minutes, and then the temperature is kept constant for 5-20 minutes for growth.
5) And opening a furnace cover after the tube furnace is naturally cooled to below 400 ℃, rapidly cooling, and cooling to room temperature to obtain a single-layer molybdenum disulfide triangular domain with single orientation or a single-layer molybdenum disulfide single crystal wafer formed by splicing the single-layer molybdenum disulfide triangular domain with single orientation.
Example 1
A commercially available 2 inch c 1 ° sapphire single crystal wafer (430 μm thick with a surface roughness <0.2 nm) was placed in an alumina crucible and annealed using a muffle furnace chamber. Heating to 1200 ℃ under the atmosphere, heating for 2h, keeping the temperature for 5h, and naturally cooling to finish annealing. The atomic force microscope photograph of the obtained sapphire single crystal is shown in fig. 1, and the annealed sapphire has a flat surface with a surface roughness of 0.2nm and uniform single-orientation steps.
And (4) taking the annealed sapphire single crystal as a substrate to grow a single-layer molybdenum disulfide single crystal film. The molybdenum foil purchased (6 cm. Times.6 cm, thickness 25 μm) was folded into a bridge shape with a height of 1cm. And (3) placing the annealed sapphire on a graphite boat, paving a layer of 2-inch carbon cloth above the sapphire, placing a bridge-shaped molybdenum foil above the sapphire and the carbon cloth, and jointly placing the sapphire and the carbon cloth in a high-temperature tubular reaction furnace. 13g elemental sulphur powder was placed 10cm upstream of the gas flow relative to the substrate. A certain amount of argon (flow 50 sccm) and oxygen (flow 3 sccm) were introduced into the quartz tube at a pressure of about 60Pa, and the gas flow was allowed to stabilize. Heating sulfur powder and substrate to 105deg.C and 1000deg.C respectively, and maintaining the temperature for 5min. After the reaction is finished, the heating program of the furnace body is automatically closed. When the temperature of the reaction cavity is reduced to 400 ℃, the tubular furnace cover is opened, rapid cooling is performed, argon and oxygen are closed after the temperature is reduced to room temperature, and a sample is taken out.
An optical micrograph of a single-orientation molybdenum disulfide triangular domain on the obtained sapphire single-crystal substrate is shown in fig. 2. It can be seen that the obtained molybdenum disulfide triangular domains are all in the same orientation on the sapphire single crystal substrate. The domain size is about 20-30 μm.
The chemical composition of molybdenum disulfide in fig. 2 was determined by raman spectroscopy, and the result is shown in fig. 3. As can be seen, the Raman spectrum of the sample has three characteristic peaks, each at 388cm -1 ,407cm -1 And 419cm -1 Where 419cm -1 Is a characteristic peak of a sapphire substrate, 388cm -1 And 407cm -1 E corresponding to molybdenum disulfide respectively 1 2g And A 1g Peaks with a 19cm distance between the peaks -1 The molybdenum disulfide triangular domains are shown to be single layer thick.
Example 2
And heating a purchased sapphire single crystal wafer (with the thickness of 500 mu m and the surface roughness of <0.2 nm) with the thickness of 2 inches c being smaller than a 1 DEG to 1350 ℃ under the atmosphere, keeping the temperature for 7 hours, and naturally cooling to finish annealing.
And (4) taking the annealed sapphire single crystal as a substrate to grow a single-layer molybdenum disulfide single crystal film. The molybdenum foil purchased (6 cm. Times.6 cm, thickness 25 μm) was folded into a bridge shape with a height of 1cm. And (3) placing the annealed sapphire on a graphite boat, paving a layer of 2-inch carbon cloth above the sapphire, placing a bridge-shaped molybdenum foil above the sapphire and the carbon cloth, and jointly placing the sapphire and the carbon cloth in a high-temperature tubular reaction furnace. 12g elemental sulphur powder was placed 10cm upstream of the gas flow relative to the substrate. A certain amount of argon (flow 60 sccm) and oxygen (flow 4 sccm) were introduced into the quartz tube at a pressure of about 80Pa, and the gas flow was allowed to stabilize. The sulfur powder and the substrate were heated to 110℃and 950℃respectively, and kept at constant temperature for 10min. After the reaction is finished, the heating program of the furnace body is automatically closed. When the temperature of the reaction cavity is reduced to 400 ℃, the tubular furnace cover is opened, rapid cooling is performed, argon and oxygen are closed after the temperature is reduced to room temperature, and a sample is taken out.
The co-oriented molybdenum disulfide triangular domains were seamlessly spliced to form a 2 inch single layer molybdenum disulfide single crystal film, as shown in fig. 4. The obtained molybdenum disulfide wafer shows good uniformity. The second harmonic signal surface scanning is carried out on the film, as shown in fig. 5, the surface scanning chart is found to show uniform contrast, which shows that the prepared molybdenum disulfide film is single crystal.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and are not limiting. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the appended claims.

Claims (10)

1. A method of transition metal sulfide single crystal wafer growth, the method comprising the steps of:
1) Annealing the single crystal sapphire;
2) Taking the annealed sapphire wafer as a substrate, placing a transition metal foil parallel to the substrate, and placing a porous barrier layer between the foil and the substrate in parallel;
3) Placing elemental sulfur upstream of the gas stream of the substrate;
4) Introducing mixed gas into a low-pressure chemical vapor deposition system, respectively heating a substrate and elemental sulfur to a set temperature after the gas flow is stable, and then keeping the temperature constant to prepare a single-orientation transition metal sulfur compound triangular domain on the substrate;
5) And the constant temperature time is prolonged, so that the triangle domains of the single-orientation transition metal sulfur compound are spliced into the transition metal sulfur compound single crystal wafer in a seamless manner.
2. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in step 1), the single crystal sapphire substrate is annealed as follows:
heating to 1100-1500 deg.C under atmospheric condition, maintaining the temperature for 5-10 hr, and naturally cooling to room temperature.
3. The method for growing a single crystal wafer of a transition metal sulfur compound according to claim 1, wherein in step 2), the thickness of the transition metal foil is 20 to 30 μm, and the transition metal foil comprises a molybdenum foil or a tungsten foil.
4. The method for growing a single crystal wafer of transition metal sulfur compound according to claim 1, wherein in step 2), the transition metal foil is folded in a bridge shape and placed parallel to the sapphire substrate, and the foil is spaced from the substrate by a distance of 0.5-2cm.
5. The method of growing a single crystal wafer of transition metal sulfur compound according to claim 1, wherein in step 2), a porous barrier layer is placed between the substrate and the transition metal foil, the barrier layer being placed against the substrate.
6. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in the step 3), the distance between the substrate and the elemental sulfur is 10 to 20cm.
7. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in the step 3), the mass of the elemental sulfur is 10 to 15g.
8. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in the step 4), the elemental sulfur and the substrate are heated respectively, the elemental sulfur is heated to 95-120 ℃, the heating temperature of the substrate and the heating temperature of the transition metal foil are 850-1000 ℃, and the constant temperature is maintained for 5-8min.
9. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in the step 4), the low pressure condition is 18 to 180Pa, the mixed gas includes argon and oxygen, the flow rate of the argon is 50 to 100sccm, and the flow rate of the oxygen is 1 to 5sccm.
10. The method for growing a transition metal sulfur compound single crystal wafer according to claim 1, wherein in the step 5), the constant temperature time is 8 to 20 minutes.
CN202310255352.0A 2023-03-16 2023-03-16 Method for growing transition metal sulfur compound single crystal wafer Pending CN117822121A (en)

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