Preparation method and application of two-dimensional molybdenum disulfide material

Abstract

The present invention belongs to the technical field of two-dimensional material preparation, and relates to a preparation method and application of a two-dimensional molybdenum disulfide material. Using molybdenum source and sulfur powder as raw materials, and inert gas as carrier gas, the raw materials are transported to the molten glass surface through an intermediate evaporation process to be deposited as solid molybdenum sulfide, and in the subsequent etching-spreading-sulfurization-precipitation process, an ultra-high-quality and ultra-large-area molybdenum disulfide single crystal domain grown at normal pressure and without hydrogenation is obtained. The single crystal domain size of the prepared two-dimensional molybdenum disulfide material can reach 1.5 cm, and then grow into a wafer-level two-dimensional molybdenum disulfide material with a size of 2 inches, and the thickness can be 1-2 layers.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional material preparation, and more specifically relates to a preparation method and application of a two-dimensional molybdenum disulfide material. Background Art

[0002] Since the first two-dimensional materials were produced by mechanical exfoliation in 2004, two-dimensional transition metal chalcogenides (TMDCs) with atomic thickness and excellent physical properties have attracted widespread attention, and it is expected that new materials will continue Moore's Law. The preparation of high-quality, large-area and large-scale two-dimensional materials is the cornerstone for measuring their basic properties and realizing their large-scale applications. The methods for preparing two-dimensional materials include mechanical exfoliation, chemical liquid exfoliation, physical vapor deposition (PVD), chemical vapor deposition (CVD), etc. Growth methods are generally divided into top-down and bottom-up methods. Although the top-down mechanical exfoliation method has made major breakthroughs, its industrial prospects still have a long way to go. The bottom-up growth method has been studied a lot, among which chemical vapor deposition (CVD) is considered to be the most suitable method for industrial two-dimensional materials.

[0003] Guided by the CVD growth mechanism, great progress has been made in recent years in the precise control of precursor selection and mass transfer processes, the exploration of catalyst mechanisms, and substrate engineering for modifying substrate surfaces. Currently, there are three paths available for large-area growth of 2D TMDCs: i) random splicing; ii) isolated growth; iii) unidirectional growth. Due to the progress in substrate engineering in recent years, single-crystalline 2D MoS2 has successfully achieved a 2-inch scale through unidirectional growth. In addition, randomly assembled polycrystalline 2D MoS2 has reached a 12-inch size.

[0004] Currently, silicon wafer-scale growth achieved by chemical vapor deposition methods is achieved by merging unidirectional domains. However, translational grain boundaries caused by imperfect stitching still exist, which is not ideal for device applications. In contrast, growing isolated domains can avoid the stitching process. However, to date, only three works have achieved the growth of millimeter-scale isolated domains, namely 2.6 mm, 1.1 mm and 1.0 mm, and the growth of isolated domains seems unable to break through the limitations of large-scale growth.

[0005] The growth of large-scale isolated single crystal MoS2 depends on the control of three factors: minimizing the density of nucleation points, maintaining lateral growth, and inhibiting longitudinal growth, which means that a high nucleation barrier and a low diffusion barrier are required during the growth process. However, achieving the optimal conditions for all three factors at the same time brings challenges. Compared with the growth of two-dimensional materials, the manufacture of high-quality single crystal bulk materials is similar to the Czochralski process, which usually grows from a seed rather than by splicing multiple crystals. The seed growth process requires large-scale and uniform liquid or solid precursors. Low nucleation density and maintenance of lateral growth can be achieved through a controlled Czochralski process. However, the liquid precursor of the Czochralski process is difficult to confine to two-dimensional space, so longitudinal growth is uncontrollable. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method and application of a two-dimensional molybdenum disulfide material, using molybdenum trioxide powder and sulfur powder as raw materials and an inert gas as a carrier gas, and transporting the raw materials to the molten glass surface through an intermediate evaporation process to deposit as solid molybdenum sulfide, and in the subsequent etching spreading-sulfurization precipitation process to obtain normal pressure, hydrogenation-free growth of ultra-high quality and ultra-large area molybdenum disulfide single crystal domains, so as to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing a two-dimensional molybdenum disulfide material, the steps comprising:

[0009] Using molybdenum source and sulfur as raw materials and inert gas as carrier gas, the raw materials are transported to the surface of molten soda-lime glass through an intermediate evaporation process to be deposited as solid molybdenum sulfide, and the two-dimensional molybdenum disulfide material is obtained through etching, spreading, and sulfurization precipitation.

[0010] Furthermore, the molybdenum source is one of molybdenum trioxide, sodium molybdate, molybdenum sulfide and molybdenum foil.

[0011] Furthermore, the amount of the molybdenum source is 1 mg to 20 mg.

[0012] Furthermore, the sulfur is sublimated sulfur.

[0013] Furthermore, the step of transporting the raw material to the surface of the molten soda-lime glass through an intermediate evaporation process to deposit solid molybdenum sulfide specifically includes:

[0014] placing sulfur in a first temperature zone, and placing a molybdenum source and soda-lime glass in a second temperature zone;

[0015] The first temperature zone is heated to 120-180°C, and the second temperature zone is heated to 500-1400°C. Inert gas is introduced during the heating process, and sulfur is transported to the second temperature zone by the inert gas, and a solid molybdenum sulfide layer is deposited on the surface of the soda-lime glass.

[0016] Preferably, the heating rate of the first temperature zone is 5 to 50° C. / min; the heating rate of the second temperature zone is 5 to 50° C. / min.

[0017] Preferably, the inert gas is argon with a flow rate of 200 to 500 sccm.

[0018] Furthermore, the specific steps of the etching and spreading are: after obtaining the solid molybdenum sulfide layer, adjusting the temperature of the second temperature zone to 900-1400° C., introducing oxygen, and etching the solid molybdenum sulfide layer to obtain a sodium molybdate precursor (sodium dimolybdate).

[0019] Preferably, the flow rate of the oxygen gas is 1 to 10 sccm.

[0020] Preferably, the temperature adjustment rate of the second temperature zone is 0-50°C / min.

[0021] The etching and spreading in the present invention includes two steps. The molybdenum oxide generated by oxygen etching the pre-deposited molybdenum disulfide solid undergoes a eutectic reaction with the sodium oxide in the glass to generate a non-volatile sodium molybdate precursor (sodium dimolybdate). The sodium molybdate precursor (sodium dimolybdate) spreads and converges on the surface of the molten glass, the tension in the liquid is destroyed, and finally the spreading of the two-dimensional film is completed.

[0022] Furthermore, the specific steps of the sulfidation precipitation are: after obtaining the sodium molybdate precursor (sodium dimolybdate), stopping the oxygen supply, and performing a sulfidation precipitation reaction to obtain the two-dimensional molybdenum disulfide material.

[0023] It should be noted that if the oxygen is introduced for too long, all the molybdenum sources will be etched and dissipated with the carrier gas, and molybdenum disulfide will not grow on the glass surface. Therefore, the time for introducing oxygen needs to be strictly controlled, and the oxygen supply should be stopped immediately when the solid molybdenum sulfide layer is converted into sodium molybdate precursor.

[0024] The present invention utilizes the liquid-liquid interface diffusion growth mechanism of two-dimensional molybdenum disulfide materials assisted by molten glass, obtains a liquid molybdenum oxide film with the assistance of liquid glass at high temperature, and then obtains large-sized molybdenum disulfide single crystal domains at ultra-fast speed through a sulfurization process. Specifically: in a pre-deposition step, sulfur vapor and a sublimated molybdenum source react on the surface of a molten soda-lime glass to deposit solid molybdenum sulfide (at this time, the molybdenum sulfide layer is thicker and has a non-two-dimensional structure), and then oxygen is used as an etchant to react with the generated molybdenum sulfide and sodium oxide in the soda-lime glass to generate a sodium molybdate precursor (sodium dimolybdate). Since the soda-lime glass is in a molten state and is a high-tension liquid, the sodium molybdate precursor (sodium dimolybdate) with a low surface tension is spread to obtain a two-dimensional liquid precursor film. Finally, in the sulfurization process, a two-dimensional molybdenum disulfide material is obtained through a sulfurization and precipitation process of supersaturated sulfur vapor. Since the two-dimensional liquid precursor is very thin, the precipitation process of this process is extremely fast, reaching 75μm / s.

[0025] The second technical solution of the present invention is to provide a two-dimensional molybdenum disulfide material prepared by the above preparation method.

[0026] The third technical solution of the present invention is to provide an application of the above-mentioned two-dimensional molybdenum disulfide material in a field effect transistor.

[0027] The present invention discloses the following technical effects:

[0028] The present invention can effectively improve the crystal quality through high-temperature liquid-solid crystallization process growth. The prepared two-dimensional molybdenum disulfide material has a large area, and the side length of the centimeter-level crystal domain can reach 1.5 cm. Multiple crystal domains can cover a five-inch glass surface (wafer level) with a thickness of 1 to 2 layers and a defect density of less than 1.0×10 13 cm -2 , which helps to improve its application performance in large-scale, high-yield, high-performance, low-power integrated circuits, optoelectronics and other fields.

[0029] The material prepared by the present invention grows at normal pressure, which can occur without vacuum equipment, and the reaction occurring at normal pressure is very rapid, with high preparation efficiency, which can reach 75 μm / s. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 Schematic diagram of the growth of two-dimensional MoS2.

[0032] Figure 2This is a preparation flow chart of the two-dimensional molybdenum disulfide material of the present invention, wherein substrate 1 is soda-lime glass substrate 2 is a silicon wafer.

[0033] Figure 3 This is a diagram of the single crystal domain size of the two-dimensional molybdenum disulfide material prepared in Example 1.

[0034] Figure 4 This is a scanning tunneling microscope image of the two-dimensional molybdenum disulfide prepared in Example 1.

[0035] Figure 5 This is a dimensional diagram of the double-layer two-dimensional molybdenum disulfide material prepared in Example 2.

[0036] Figure 6 This is a dimensional diagram of the wafer-level two-dimensional molybdenum disulfide material prepared in Example 3.

[0037] Figure 7 This is a single crystal domain size diagram of a two-dimensional molybdenum disulfide material prepared using molybdenum sulfide, sodium molybdate or molybdenum foil as raw materials, where a is molybdenum sulfide, b is sodium molybdate, and c is molybdenum foil.

[0038] Figure 8 This is a diagram of the single crystal domain size of the two-dimensional molybdenum disulfide prepared in Comparative Example 1.

[0039] Fig. 9 This is a diagram of the single crystal domain size of the pseudo single crystal TMDCs wafer prepared in Comparative Example 2. DETAILED DESCRIPTION

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0044] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0045] Unless otherwise specified, the room temperature and normal temperature in the specific embodiments of the present invention are both 20-30°C.

[0046] In a specific embodiment of the present invention, the inert gas is argon.

[0047] Figure 1 Schematic diagram of the growth of two-dimensional MoS2.

[0048] Figure 2 This is a preparation flow chart of the two-dimensional molybdenum disulfide material of the present invention, wherein substrate 1 is soda-lime glass and substrate 2 is a silicon wafer.

[0049] Example 1

[0050] The preparation steps of centimeter-scale two-dimensional MoS2 single crystal domain materials are as follows:

[0051] S1. Treatment of the growth substrate: using acetone, isopropanol and water to ultrasonically clean the surface of the soda-lime glass for 5 minutes respectively, drying with nitrogen, and then performing oxygen ion etching to obtain a glass substrate with a clean surface;

[0052] S2, furnace baking and inert gas protection: heat the tube furnace to 500 degrees Celsius and keep it warm, while introducing inert protective gas to exclude air;

[0053] S3, dual-temperature zone heating growth: sublimated sulfur is placed in the first temperature zone, and 5 mg of MoO3 powder and soda-lime glass are sequentially pushed into the second temperature zone (soda-lime glass is supported by a silicon wafer in order to maintain the shape of soda-lime glass at high temperatures), the distance between the molybdenum source and the soda-lime glass is about 12 to 15 cm, the first temperature zone is heated to 130°C at a heating rate of 50°C / min, and the second temperature zone is heated to 1000°C at a heating rate of 20°C / min, and the sublimated sulfur in the first temperature zone is transported to the second temperature zone in the form of vapor under an inert gas flow (100 sccm), and a solid molybdenum sulfide layer is deposited on the surface of the soda-lime glass;

[0054] S4, after obtaining the solid molybdenum sulfide layer, introducing oxygen (1-10 sccm) at 1000° C. to etch the solid molybdenum sulfide layer to obtain a sodium molybdate precursor (sodium dimolybdate);

[0055] S5. After obtaining the sodium molybdate precursor (sodium dimolybdate), stop supplying oxygen, carry out a sulfidation precipitation reaction, and then cool to room temperature to obtain a centimeter-scale two-dimensional molybdenum disulfide material.

[0056] The single crystal domain size diagram of the centimeter-scale two-dimensional MoS2 material prepared in step S5 is shown in Figure 3 As shown; the scanning tunneling microscope image of the centimeter-scale two-dimensional molybdenum disulfide material prepared in step S5 is as shown Figure 4 As shown, the brighter spots are molybdenum atoms and the darker spots are sulfur atoms.

[0057] Example 2

[0058] The preparation steps of double-layer two-dimensional molybdenum disulfide material are as follows:

[0059] S1. Treatment of the growth substrate: using acetone, isopropanol and water to ultrasonically clean the surface of the soda-lime glass for 5 minutes respectively, drying with nitrogen, and then performing oxygen ion etching to obtain a glass substrate with a clean surface;

[0060] S2, furnace baking and inert gas protection: heat the tube furnace to 500 degrees Celsius and keep it warm, while introducing inert protective gas to exclude air;

[0061] S3, dual-temperature zone heating growth: sublimated sulfur is placed in the first temperature zone, and 8 mg of MoO3 powder and soda-lime glass are sequentially pushed into the second temperature zone (soda-lime glass is supported by a silicon wafer in order to maintain the shape of soda-lime glass at high temperatures), the distance between the molybdenum source and the soda-lime glass is about 12 to 15 cm, the first temperature zone is heated to 160°C at a heating rate of 50°C / min, and the second temperature zone is heated to 1000°C at a heating rate of 20°C / min, and the sublimated sulfur in the first temperature zone is transported to the second temperature zone in the form of vapor under an inert gas flow (150 sccm), and a solid molybdenum sulfide layer is deposited on the surface of the soda-lime glass;

[0062] S4, after obtaining the solid molybdenum sulfide layer, introducing oxygen (1-10 sccm) at 1100° C. to etch the solid molybdenum sulfide layer to obtain a sodium molybdate precursor (sodium dimolybdate);

[0063] S5. After obtaining the sodium molybdate precursor (sodium dimolybdate), stop supplying oxygen, carry out a sulfidation precipitation reaction, and then cool to room temperature to obtain a double-layer two-dimensional molybdenum disulfide material.

[0064] The single crystal domain size diagram of the double-layer two-dimensional MoS2 material prepared in step S5 is shown in Figure 5 shown.

[0065] Example 3

[0066] The preparation steps of wafer-level two-dimensional molybdenum disulfide materials are as follows:

[0067] S1. Treatment of the growth substrate: using acetone, isopropanol and water to ultrasonically clean the surface of the soda-lime glass for 5 minutes respectively, drying with nitrogen, and then performing oxygen ion etching to obtain a glass substrate with a clean surface;

[0068] S2, furnace baking and inert gas protection: heat the tube furnace to 500 degrees Celsius and keep it warm, while introducing inert protective gas to exclude air;

[0069] S3, dual-temperature zone heating growth: sublimated sulfur is placed in the first temperature zone, and 10 mg of MoO3 powder and soda-lime glass are sequentially pushed into the second temperature zone (soda-lime glass is supported by a silicon wafer in order to maintain the shape of soda-lime glass at high temperatures), the distance between the molybdenum source and the soda-lime glass is about 12 to 15 cm, the first temperature zone is heated to 150°C at a heating rate of 50°C / min, and the second temperature zone is heated to 1100°C at a heating rate of 20°C / min, and the sublimated sulfur in the first temperature zone is transported to the second temperature zone in the form of vapor under an inert gas flow (100 sccm), and a solid molybdenum sulfide layer is deposited on the surface of the soda-lime glass;

[0070] S4, after obtaining the solid molybdenum sulfide layer, introducing oxygen (1-10 sccm) at 1100° C. to etch the solid molybdenum sulfide layer to obtain a sodium molybdate precursor (sodium dimolybdate);

[0071] S5. After obtaining the sodium molybdate precursor (sodium dimolybdate), stop supplying oxygen, carry out a sulfidation precipitation reaction, and then cool to room temperature to obtain a wafer-level two-dimensional molybdenum disulfide material. Transfer the wafer-level two-dimensional molybdenum disulfide material to a silicon wafer and measure its size. Figure 6 shown.

[0072] Example 4

[0073] The only difference from Example 1 is that the MoO3 powder is replaced with an equal mass of molybdenum sulfide, sodium molybdate or molybdenum foil.

[0074] Figure 7 This is a single crystal domain size diagram of a two-dimensional molybdenum disulfide material prepared using molybdenum sulfide, sodium molybdate or molybdenum foil as raw materials, where a is molybdenum sulfide, b is sodium molybdate, and c is molybdenum foil.

[0075] Comparative Example 1

[0076] The steps for preparing two-dimensional molybdenum disulfide by conventional chemical vapor deposition are:

[0077] S1. Evaporate / sublimate the precursor into gas at high temperature and transfer it to the substrate area under the action of carrier gas.

[0078] S2. On the substrate surface, first, some precursor gas molecules break through the adsorption barrier and adsorb on the glass substrate surface, and then break through the nucleation barrier to undergo chemical reactions and form nuclei. At the same time, some gas molecules complete desorption and leave the substrate surface.

[0079] S3, after nucleation, the precursor continues to grow near the nucleation point in two ways: 1. Breakthrough E1 directly adsorbs on the edge of the nucleation point and completes bonding and growth along the edge; 2. Breakthrough E2 first adsorbs on the substrate surface and completes aggregation, bonding and growth at the edge of the nucleation point through diffusion on the substrate surface. In fact, E1 is much larger than E2, so the adsorption and diffusion of the substrate surface are very important factors affecting the growth of two-dimensional materials.

[0080] Figure 8 The single crystal domain size diagram of the two-dimensional molybdenum disulfide prepared in Comparative Example 1 is shown in FIG. Figure 8 It can be seen that the two-dimensional molybdenum disulfide material prepared is relatively small in area, with a side length of only 2.6 mm, which is quite different from the size prepared in Example 1 of the present application.

[0081] Comparative Example 2

[0082] The steps for splicing micron-sized particles to synthesize pseudo-single-crystalline TMDCs wafers with a large number of grain boundaries are:

[0083] S1. By greatly increasing the mass flux, the nucleation barrier is broken and a large number of nucleation sites are accumulated on the substrate surface.

[0084] S2. Use high mass flux to break through the diffusion barrier and complete the growth of a large number of micron-sized crystal domains on the substrate surface.

[0085] S3. When micron-sized crystal domains grow to connect with adjacent crystal domains, randomly oriented crystal domains will produce grain boundaries during the splicing process.

[0086] Fig. 9The single crystal domain size diagram of the pseudo single crystal TMDCs wafer prepared in Comparative Example 2 is shown in FIG. Fig. 9 It can be seen that the crystal domains of the pseudo single crystal TMDCs wafer prepared in Comparative Example 2 have obvious grain boundaries, which affects the stability as a channel material.

[0087] The present invention improves the growth method and controls the growth conditions. The defect density of the prepared material obtained by statistics is less than 1.0×10 13 cm -2 Low defect density means high uniformity and high stability of the material, which is conducive to the preparation of large-scale high-quality integrated circuits.

[0088] In the present invention, the molybdenum source is transferred in a manner that after sublimation, it is carried away by a carrier gas to generate a molybdenum sulfide solid to complete a gas-solid process, oxygen is introduced to complete a solid-liquid process, and after the oxygen supply is stopped, a liquid-solid process is completed to form a two-dimensional molybdenum disulfide. When the amount of molybdenum source is increased, more competition will occur between the crystal domains, and the final product formed is a film of wafer-level crystal domain splicing, so that the substrate surface is full of spliced ​​films, and when the amount is lower, centimeter-level single crystal domains are formed.

[0089] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0090] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a two-dimensional molybdenum disulfide material, characterized in that the steps include: Using molybdenum source and sulfur as raw materials and inert gas as carrier gas, the raw materials are transported to the surface of molten soda-lime glass through an intermediate evaporation process to deposit solid molybdenum sulfide, and the two-dimensional molybdenum disulfide material is obtained through etching, spreading, and sulfurization precipitation; The step of transporting the raw material to the surface of the molten soda-lime glass through an intermediate evaporation process to deposit solid molybdenum sulfide comprises: placing sulfur in a first temperature zone, placing a molybdenum source and soda-lime glass in a second temperature zone; heating the first temperature zone to 120-180° C., heating the second temperature zone to 500-1400° C., introducing an inert gas during the heating process, and transporting sulfur to the second temperature zone by the inert gas, and depositing a solid molybdenum sulfide layer on the surface of the soda-lime glass; The etching and spreading step comprises: after obtaining the solid molybdenum sulfide layer, adjusting the temperature of the second temperature zone to 900-1400° C., introducing oxygen, and etching the solid molybdenum sulfide layer to obtain sodium dimolybdate; The sulfidation precipitation step is: after obtaining the sodium dimolybdate, stopping the oxygen supply, and performing a sulfidation precipitation reaction to obtain the two-dimensional molybdenum disulfide material.

2. The preparation method according to claim 1, characterized in that: During the deposition process of the solid molybdenum sulfide layer, the heating rate of the first temperature zone is 5-50°C / min; the heating rate of the second temperature zone is 5-50°C / min; the inert gas is argon with a flow rate of 200-500sccm.

3. The preparation method according to claim 1, characterized in that: During the etching and spreading process, the flow rate of the oxygen gas is 1 to 10 sccm; and the temperature adjustment rate of the second temperature zone is 0 to 50° C. / min.

4. The preparation method according to claim 1, characterized in that: The sulfur is sublimated sulfur; the molybdenum source is one of molybdenum trioxide, sodium molybdate, molybdenum sulfide and molybdenum foil; and the amount of the molybdenum source is 1 mg to 20 mg.

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