CN115156524A - Ectopic nucleation double-layer MoS 2 Nanosheet and preparation method thereof - Google Patents

Ectopic nucleation double-layer MoS 2 Nanosheet and preparation method thereof Download PDF

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CN115156524A
CN115156524A CN202210992813.8A CN202210992813A CN115156524A CN 115156524 A CN115156524 A CN 115156524A CN 202210992813 A CN202210992813 A CN 202210992813A CN 115156524 A CN115156524 A CN 115156524A
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mos
layer
double
substrate
molybdenum
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周喻
李成
范秀莲
邹路玮
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Central South University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0551—Flake form nanoparticles
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/305—Sulfides, selenides, or tellurides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber

Abstract

The invention belongs to the field of nano materials, and discloses a double-layer molybdenum disulfide nanosheet with ectopic nucleation and a preparation method thereof. Molybdenum trioxide and sulfur powder are used as precursors, sodium chloride is used as a fluxing agent, and an inert gas argon is used as a carrier gas to react at a certain temperature. The invention introduces the disturbance to the growth condition by a simple method, namely, the airflow direction of the surface of the substrate and the change of the concentration of a local reactant are regulated and controlled by utilizing the specific inclination angle of the substrate silicon wafer, and the nucleation site of the top layer molybdenum disulfide deviates from the nucleation site of the bottom layer molybdenum disulfide in the heating and heat preservation processes, thereby forming a double-layer stacking mode deviating from the central nucleation site of the bottom layer. Under the growth condition without disturbance, the double-layer molybdenum disulfide nanosheet grows in an orthotopic nucleation mode. The method can be used for preparing the double-layer molybdenum disulfide nanosheet with ectopic nucleation growth, effectively reduces a double-layer stacking mode with stable thermodynamics, realizes the regulation and control of the nucleation position of the double-layer nanosheet, and is simple and feasible.

Description

Ectopic nucleation double-layer MoS 2 Nanosheet and preparation method thereof
Technical Field
The invention belongs to the field of inorganic nano materials, and particularly relates to a double-layer MoS with ectopic nucleation 2 Nanosheets and a method for preparing the same.
Background
With the continuous development of modern electronic and optoelectronic devices towards high integration and miniaturization, there is an urgent need to develop new functional materials, and to develop materials and device technologies compatible with the conventional silicon process planar device structure, such as transition metal sulfide two-dimensional materials. As one member of a transition metal sulfide family, molybdenum disulfide has an adjustable band gap of 1.2-1.9eV, and has a wide application prospect in the aspects of logic devices, integrated circuits, photoelectrons and the like. The molybdenum disulfide is a layered material, and each layer of molybdenum disulfide is combined in a covalent bond mode by embedding a molybdenum atomic layer in the upper and lower sulfur atomic layers. Compared with a single-layer molybdenum disulfide material formed by three atomic layers, the double-layer molybdenum disulfide material has richer physical properties, such as higher mobility, molar flat band and the like. Meanwhile, the characteristics of photoluminescence, light absorption, photocurrent and the like of the molybdenum disulfide layered material show strong dependence on the number of layers and the stacking sequence. Therefore, the molybdenum disulfide layered material with a specific structure has great potential in the aspects of next-generation electronic and photoelectric devices.
The current research focus of molybdenum disulfide is single-layer or few-layer, the research on double-layer molybdenum disulfide is less, even if a scheme for preparing double-layer or multi-layer molybdenum disulfide in a small amount is provided, the obtained co-position nucleation molybdenum disulfide material is basically the scheme for preparing the molybdenum disulfide material by the co-position nucleation, and the scheme for preparing the molybdenum disulfide material by the hetero-position nucleation is not provided. The preparation method of the molybdenum disulfide thin layer comprises a mechanical stripping method, a liquid phase stripping method, a gas phase growth method and the like. Mechanical stripping methods are time consuming, cannot be used for large scale material preparation, and cannot control the number of layers, size, orientation, phase structure of the prepared material. The molybdenum disulfide thin layer prepared by the liquid phase stripping method has poor quality and small size. The vapor phase growth method is a powerful means for preparing high-quality two-dimensional materials, wherein the chemical vapor deposition method is the most widely used method for preparing the lamellar molybdenum disulfide so far, and can ensure that high-quality large-area monolayer molybdenum disulfide is prepared on the premise of low cost, large scale and controllability. However, the layered molybdenum disulfide single crystal grown by chemical vapor deposition still has the problems of small size, difficulty in controlling thickness, poor quality and the like. CN113045213B discloses a preparation method of a molybdenum disulfide planar homojunction, wherein a pretreated soda-lime glass substrate is placed on the surface of a molybdenum foil A, the surface of the soda-lime glass substrate is covered with a molybdenum foil B subjected to preoxidation treatment, inert gas is introduced, the reaction cavity is kept at normal pressure, and the molybdenum foil A/the soda-lime glass substrate/the molybdenum foil B are heated to the melting temperature of the soda-lime glass substrate; placing a quartz boat containing sulfur powder at the upstream of the inert gas, and heating the quartz boat to evaporate the sulfur powder; and after the growth time is finished, obtaining a single-layer/double-layer alternate molybdenum disulfide planar homogeneous film with a single crystal structure on the surface of the soda-lime glass substrate close to the molybdenum foil B. Although the method can prepare the molybdenum disulfide planar homojunction film with large area, high quality and high electron mobility, the operation is complex, the requirement on parameters is strict, and only the molybdenum disulfide film with the orthotopic nucleation can be obtained. CN114411148A is prepared by preparing a metal film or a metal oxide film on a silicon wafer as a precursor film by a thermal evaporation coating method, placing the silicon wafer coated with the precursor film and a substrate in an evaporation boat face to face, vulcanizing the precursor film by a chemical vapor deposition method, and growing a two-dimensional transition metal chalcogenide on the substrate. By the chemical vapor deposition face-to-face growth method, the distance between the precursor film and the substrate can be controlled, the distance between nucleation sites of the two-dimensional material and the size of a triangle can be changed, the controllability of the layer number of the two-dimensional material is realized, and the method can be further used for preparing large-area or large-size two-dimensional materials. The method needs to deposit a precursor layer on a substrate, has complex process and can only obtain the molybdenum disulfide film with in-situ nucleation. CN113957538A provides a preparation method of a double-layer molybdenum sulfide crystal material with different coverage rates, the preparation of a double-layer molybdenum sulfide two-dimensional structure with different coverage rates is realized by a one-step chemical vapor deposition method, specifically, a molybdenum foil is unfolded and placed in a quartz boat, a substrate is obliquely and reversely buckled right above the molybdenum foil, and one end of the substrate is contacted with the molybdenum foil. However, the method only obtains the molybdenum disulfide film with in-situ nucleation, and does not describe any content of preparing molybdenum disulfide by ex-situ nucleation. CN104058458B also adopts chemical vapor deposition to deposit two-dimensional molybdenum disulfide on the surface of a substrate by taking elemental molybdenum metal and sulfur powder as sources, wherein the controlled growth of a high-quality molybdenum disulfide single-layer or double-layer structure is realized by optimizing preparation parameters such as deposition temperature, growth time and the like, specifically, the sulfur source, the molybdenum source and the substrate are placed on a supporting plane, and the substrate and the supporting plane form an inclination angle of 0-60 degrees, preferably 0-45 degrees, most preferably 30 degrees, but the method only obtains a molybdenum disulfide film with in-situ nucleation, and does not describe any content of preparing molybdenum disulfide by ex-situ nucleation.
So far, the attention on the double-layer molybdenum disulfide is mostly limited to the samples grown by the orthotopic nucleation, and the samples grown by the ectopic nucleation are rarely studied, and a scheme for preparing the layered ectopic nucleation molybdenum disulfide is not disclosed. Since the micro-environment around the nucleation site determines the orientation of the molybdenum disulfide during the chemical vapor deposition process, two of the double layers of molybdenum disulfide with the same nucleation centers will preferentially grow in the thermodynamically stable state, i.e., AA-stacking or AB-stacking. The invention provides a method for controlling ectopic nucleation through air flow disturbance, wherein two layers of molybdenum disulfide nucleate at different positions to obtain double-layer corner molybdenum disulfide with a specific structure. The corner two-dimensional material, particularly the corner molybdenum disulfide, can form molar superlattice adjustment interlayer coupling through a corner, so that the structural dispersion relation of an electronic energy band is adjusted and controlled, a brand-new opportunity is provided for researching flat band and generated associated electronic effects, and meanwhile, the structural material has great potential application in researching phenomena such as a strong associated insulator, unconventional superconduction, a topological old insulator and the like, and in new electronic devices and photoelectronic devices adjusted and controlled by molar periodic potential. The invention provides a dual-layer MoS with ectopic nucleation 2 The nanosheet provides a simple ectopic nucleation growth method for changing the core position through airflow disturbance, and provides a new idea for regulating and controlling the interlaminar distortion angle.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background art, and provide an ectopic nucleation double-layer molybdenum disulfide material and a preparation method thereof.
In one embodiment of the invention, the ectopically nucleated, double-layered MoS 2 The nano-sheet consists of an upper layer and a lower layer of MoS 2 Stacked with a top layer of MoS 2 Has nucleation sites deviated from the underlying MoS 2 The center position of (a).
In one embodiment of the invention, the upper and lower two-layered MoS 2 MoS in nanosheets 2 The crystal domains are triangular or hexagonal, wherein the top layer MoS 2 The side length of the crystal grain is 2-5 mu m, and the bottom layer MoS 2 The side length of the crystal grain is 3-15 mu m.
The invention relates to an ectopic nucleated double-layer MoS 2 The preparation method of the nano-sheet is characterized in that the double-layer MoS is grown on the surface of the substrate in one step by utilizing chemical vapor deposition 2 Nanosheets, wherein in a quartz tube of a chemical vapor deposition apparatus, a substrate is placed obliquely above a molybdenum evaporation source, being horizontally inclined at an appropriate angle along the direction of gas flow. The substrate is horizontally inclined by 1-3 degrees and is placed above the molybdenum evaporation source, and the substrate is SiO 2 The molybdenum evaporation source is molybdenum trioxide.
In one embodiment of the invention, the number of the substrates is two or more, the two or more substrates are stacked above the molybdenum evaporation source in the form of disturbed gas flow, and the vertical height between the adjacent substrates is about 2-4 mm.
In one embodiment of the invention, two SiO dimensions of 1X 1cm and 1X 2cm, respectively 2 a/Si substrate of 1X 1cm SiO 2 The Si substrate is placed on 1X 2cm of SiO 2 The vertical distance of the position obliquely below and behind the/Si substrate is 3mm.
In one embodiment of the invention, the method comprises the steps of:
(1) Taking molybdenum trioxide powder as a molybdenum evaporation source, sodium chloride as a fluxing agent, taking elemental sulfur powder as a sulfur evaporation source, and sequentially placing the sulfur evaporation source, the molybdenum evaporation source and the substrate in a corresponding temperature interval in a quartz tube along the airflow direction;
(2) Mixing SiO 2 the/Si substrate is obliquely stacked above the molybdenum evaporation source in an airflow disturbance mode;
(3) After the inert gas is used for discharging the air in the quartz tube, the tube furnace is heated, and a proper amount of inert gas is continuously introduced to be used as carrier gas, so that MoS is completed 2 And (4) growing the nanosheets.
The reaction device for implementing the preparation method comprises a quartz tube, a tubular furnace and a heating belt, wherein a middle cavity of the quartz tube is arranged in a central constant-temperature area of the tubular furnace, molybdenum trioxide powder is arranged in the central constant-temperature area, and a substrate is arranged in the constant-temperature area above the molybdenum trioxide powder; the chamber at the upstream of the quartz tube is a heating zone, and sulfur powder is placed in the upstream heating zone area.
The gas inlet of the quartz tube is provided with a gas valve, wherein a temperature area close to the sulfur powder is a gas inlet valve; the other end is an air outlet.
In the reaction, a heating device is utilized to heat a central constant-temperature area containing molybdenum trioxide and the substrate to reach a deposition temperature range, carrier gas is introduced, and chemical vapor deposition reaction is carried out to obtain the double-layer molybdenum disulfide ex-situ growth nanosheet material. In the step (1), the corresponding temperature range of the molybdenum evaporation source is 650-720 ℃, and preferably 680-700 ℃; the corresponding temperature range of the sulfur evaporation source is 170-220 ℃, and 190-200 ℃ is preferred; the SiO 2 The temperature range corresponding to the/Si substrate is 650-720 deg.C, preferably 680-700 deg.C. If the substrate temperature is lower than the lower limit of the preferred range, the chemical reaction of the molybdenum source and the sulfur source is slow, and a monolayer of molybdenum disulfide nanosheets are easy to appear. If the substrate temperature is higher than the upper limit of the preferred range, the molybdenum source and the sulfur source are supplied quickly, a molybdenum disulfide film is easily generated, and a double-layer ectopically-grown molybdenum disulfide nanosheet is difficult to obtain.
The inert gas is argon, and the flow rate of the carrier gas is 10-50sccm, preferably 20-30sccm. If the carrier gas flow is below the selected lower range limit, excessive deposition will occur on the substrate surface and it will be difficult to obtain clean, free-standing nanoplatelets. If the carrier gas flow is higher than the upper limit of the selected range, intermediate products such as molybdenum trioxide nanosheets or molybdenum oxysulfide nanosheets and the like which grow vertically can appear on the surface of the substrate, the obtained nanosheets are no longer single molybdenum disulfide nanosheets, the product is rich in impurities and complex in components, and the influence on the photoelectric performance and the like of the material is large.
The vertical height between the adjacent substrates is 2-4mm, preferably 3mm. If the vertical distance between the substrates is higher than 4mm, the molybdenum disulfide supply speed is too high, most of the substrate surface area is a molybdenum disulfide polycrystalline film, and only a small amount of double-layer molybdenum disulfide nanosheets grow ex-situ. If the vertical distance between the substrates is less than 2mm, the molybdenum disulfide supply speed is too slow, and MoS 2 Few nucleation sites exist, but the molybdenum disulfide on the top layer is easy to form a regular triangle due to insufficient supply.
In the invention, under the coordination of the temperature interval and the carrier gas with specific flow rate, the MoS with double-layer in-situ growth can be obtained on the silicon chip substrate placed horizontally without inclination angle 2 Nanosheets; under a specific airflow disturbance mode, the substrate is placed above the molybdenum evaporation source to obtain the MoS with double-layer ectopic growth 2 The shape and the crystallization quality of the nanosheet of molybdenum disulfide grown in the two modes are good.
The thickness of the oxide layer of the silicon-silicon dioxide substrate is 285 +/-10 nm, and the total thickness of the substrate is 500 +/-10 mu m.
Preferably, the molybdenum source and the sulfur source are both contained in porcelain boats.
Preferably, the vapor deposition growth time of the invention is preferably 3-10min; further preferably 5 to 8min.
In one aspect of the present application the ectopically nucleated bilayer MoS is obtained 2 The nano-sheet consists of an upper layer and a lower layer of MoS 2 Stacked nano sheets with upper and lower layers of MoS 2 MoS in nanosheets 2 The domains are independent and are triangular or hexagonal, wherein the upper layer MoS 2 The side length of the triangular plate is 2-5 μm, and the lower layer MoS 2 The side length of the triangular plate is 3-15 μm.
The invention adopts a simpler scheme to obtain the heterotopic growth double-layer MoS 2 Nanosheets, the bilayer MoS 2 The ectopic nucleation growth is a non-equilibrium dynamic process formed by regulating thermodynamic and kinetic factors in vapor deposition growth, and then the phenomena of abnormal stacking and coupling occur. More specifically, during the ectopic nucleation growth of the double-layer molybdenum disulfide, the inclination angle regulation surface of the substrate relative to the horizontal plane is changed by the creative meansThe air flow direction of the interface layer and the concentration of the local reactant can regulate the movement trend of molecules, so that the ectopic nucleation growth of the double-layer nanosheets can be induced. However, the inclination is different from the conventional prior chemical vapor deposition in the background art, and the applicant creatively uses the substrate to be inclined above the molybdenum evaporation source at a certain inclination angle along the axial direction of the quartz tube, wherein the inclination angle is 1-3 degrees, and the specific inclination is adopted to match the whole chemical vapor deposition parameter setting, so that the relative positions of the nucleation points of the top layer and the bottom layer can be changed during the heating and heat preservation processes. By breaking the molecular dynamics equilibrium state, a sample with double-layer molybdenum disulfide ectopic nucleation growth can be prepared.
In addition, the double-layer molybdenum disulfide ectopic nucleation growth is a non-equilibrium stacking mode, and a new thought can be provided for the growth of the double-layer molybdenum disulfide with small-angle torsion.
In conclusion, compared with the prior art, the preparation method is simple and convenient, the preparation process is simple, the repeatability is good, the yield is high, the sample crystallization quality is high, and the ectopic nucleation double-layer molybdenum disulfide nanosheet with higher quality can be obtained by adopting exquisite and simple operation.
Drawings
FIG. 1 is a schematic diagram of an experiment used in the present invention to grow a bilayer of ectopic molybdenum disulfide;
FIG. 2 is a schematic diagram of an experiment used in the growth of a bilayer of isotopically-distributed molybdenum disulfide according to the present invention;
figure 3 is an optical microscope image of a bilayer ex-situ grown molybdenum disulfide nanoplate prepared in example 1;
figure 4 is an optical microscope image of a bilayer of homotopically grown molybdenum disulfide nanoplates prepared in example 2;
figure 5 is an optical microscope photograph of the bilayer ex-situ grown molybdenum disulfide nanoplates prepared in example 3;
figure 6 is an optical microscope photograph of the bilayer ex-situ grown molybdenum disulfide nanoplates prepared in example 4;
fig. 7 is a raman spectrum of the double-layer ectopically-grown molybdenum disulfide nanosheet prepared in example 1.
Detailed Description
The invention is further illustrated by the following specific examples. The invention adopts a normal pressure chemical vapor deposition method, wherein a molybdenum source is arranged in a central constant temperature area of a quartz tube, and a sulfur source is arranged in a low temperature area at the upstream of the quartz tube. The inner diameter of the quartz tube used in the examples of the present invention and the comparative examples was 20mm. The operation steps of the embodiment are as follows: introducing large-flow argon for 15 minutes to remove air in the quartz tube, and regulating the argon to be the preferred flow when the temperature is raised to the end of heat preservation; closing the sulfur source after the heat preservation is finished, opening the furnace, and naturally cooling to room temperature, thereby preparing the double-layer ectopically-grown MoS on the silicon wafer substrate 2 A nanosheet.
Example 1
Weighing 3-6mg of molybdenum trioxide powder and 1-3mg of sodium chloride, uniformly mixing, placing in a porcelain boat with the length, width and thickness of 97 multiplied by 14.5 multiplied by 2.4mm, and placing 25-35mg of sulfur powder in a porcelain boat with the length, width and thickness of 72 multiplied by 12 multiplied by 2.2 mm. As shown in the experimental schematic diagram of FIG. 1, a molybdenum source is placed in a constant temperature region of 690 ℃, and SiO laminated in a step-shaped inclined manner of 1-3 DEG is placed 2 the/Si substrate is arranged behind the molybdenum source, the vertical distance between the lower substrate and the molybdenum source is controlled to be about 3mm, and the vertical distance between the upper substrate and the lower substrate is also controlled to be about 3mm. Before the temperature rise is started, argon gas with the flow rate of 120sccm is introduced into the quartz tube, and air in the quartz tube is discharged. 30sccm of argon gas is introduced in the temperature rising and heat preservation stages, the temperature is raised to 690 ℃ at the speed of 28 ℃/min, and the heat preservation is carried out for 8min. After the heat preservation is finished, opening the furnace, naturally cooling to room temperature, and closing the air flow to obtain the double-layer ectopic growth MoS 2 Nanosheets.
FIG. 3 is a diagram of the double layer ectopically grown MoS prepared in example 1 2 The optical microscopic picture of the nano-sheet shows that the method produces the MoS with ectopic nucleation growth 2 And (3) sampling. When the local S source is excessive, the boundary of the nanosheet is easy to form a rounded corner edge; when the local Mo source is excessive, the boundary of the nanosheet is easy to form a shield edge; when the ratio of the local Mo source to the S source is proper, the nanosheets are straight-sided. FIG. 7 is a Raman spectrum of a sample prepared in this example at 383.3cm -1 、405.8cm -1 The obvious characteristic peak characterizes the materialThe material is MoS 2 And the sample has good crystallization quality.
Example 2
Compared with example 1, the difference is that the silicon wafers are not placed in an inclined stacking manner, but are placed horizontally, as shown in the experimental schematic diagram of fig. 2.
Weighing 3-6mg of molybdenum trioxide powder and 1-3mg of sodium chloride, uniformly mixing, placing in a porcelain boat with the length, width and thickness of 97 multiplied by 14.5 multiplied by 2.4mm, and placing 25-35mg of sulfur powder in a porcelain boat with the length, width and thickness of 72 multiplied by 12 multiplied by 2.2 mm. Placing a molybdenum source in a 690 ℃ constant temperature area, and placing SiO 2 The Si substrate is horizontally placed in a 690 ℃ temperature zone, and the distance between the substrate and the molybdenum source is controlled to be about 3mm. Before the temperature rise is started, argon gas with the flow rate of 120sccm is introduced into the quartz tube, and the air in the quartz tube is discharged. 30sccm argon is introduced in the heating and heat preservation stages, the temperature is raised to 690 ℃ at the speed of 28 ℃/min, and the heat preservation is carried out for 8min. After the heat preservation is finished, opening the furnace, naturally cooling to room temperature, and closing the air flow to obtain the double-layer MoS with homotopic growth 2 Nanosheets.
FIG. 4 shows the dual layer homotopically grown MoS prepared in example 2 2 Optical microscopy of nanoplatelets.
Example 3
Compared with example 1, the difference is that the substrate is provided with two or more obliquely stacked silicon wafers, and the distance between the adjacent silicon wafers is 1.5mm.
3-6mg of molybdenum trioxide powder and 1-3mg of sodium chloride are uniformly mixed and placed in a porcelain boat with the length, width and thickness of 97 multiplied by 14.5 multiplied by 2.4mm, and 25-35mg of sulfur powder is placed in a porcelain boat with the length, width and thickness of 72 multiplied by 12 multiplied by 2.2 mm. Placing a molybdenum source in a 690 ℃ constant temperature area, and placing SiO 2 Placing the Si substrate horizontally in a 690 deg.C temperature zone, and stacking step-like SiO 2 the/Si substrate is arranged behind the molybdenum source, the vertical distance between the lower substrate and the molybdenum source is controlled to be about 4mm, the vertical distance between the upper substrate and the lower substrate is controlled to be about 1.5mm, namely the vertical distance between two adjacent silicon wafers is controlled to be about 1.5mm. Before the temperature rise is started, argon gas with the flow rate of 120sccm is introduced into the quartz tube, and air in the quartz tube is discharged. 30sccm argon is introduced in the heating and heat preservation stages, the temperature is raised to 690 ℃ at the speed of 28 ℃/min, and the heat preservation is carried out for 8min. After the heat preservation is finishedOpening the furnace, naturally cooling to room temperature, and closing the air flow to obtain the double-layer ectopic growth MoS 2 A nanosheet.
Fig. 5 is an optical microscope photograph of the bilayer ex-situ grown molybdenum disulfide nanosheets produced in example 3. It can be seen from the figure that this method results in ex-situ nucleated MoS with two stacked layers 2 Its bottom layer MoS 2 The size was about 4-6 times that of example 1 due to the small distance between adjacent wafers, moS 2 The feeding speed of (2) is slow, and the number of nucleation sites is small, so that the sample size is large. But its top layer MoS 2 Is in the shape of a Chinese character 'ren', which is due to MoS 2 The starvation resulted in no growth into regular triangles.
Example 4
Compared with example 1, the difference is that the substrate is provided with two or more obliquely stacked silicon wafers, and the distance between the adjacent silicon wafers is 4.5mm.
3-6mg of molybdenum trioxide powder and 1-3mg of sodium chloride are uniformly mixed and placed in a porcelain boat with the length, width and thickness of 97 multiplied by 14.5 multiplied by 2.4mm, and 25-35mg of sulfur powder is placed in a porcelain boat with the length, width and thickness of 72 multiplied by 12 multiplied by 2.2 mm. Placing a molybdenum source in a 690 ℃ constant temperature area, and placing SiO 2 Placing the Si substrate horizontally in a 690 deg.C temperature zone, and stacking step-like SiO 2 the/Si substrate is arranged behind the molybdenum source, the vertical distance between the lower substrate and the molybdenum source is controlled to be about 2mm, the vertical distance between the upper substrate and the lower substrate is controlled to be about 4.5mm, namely the vertical distance between the two silicon wafers is controlled to be about 4.5mm. Before the temperature rise is started, argon gas with the flow rate of 120sccm is introduced into the quartz tube, and air in the quartz tube is discharged. 30sccm argon is introduced in the heating and heat preservation stages, the temperature is raised to 690 ℃ at the speed of 28 ℃/min, and the heat preservation is carried out for 8min. After the heat preservation is finished, opening the furnace, naturally cooling to room temperature, and closing the air flow to obtain partial double-layer ectopic growth MoS 2 Nanosheets.
FIG. 6 shows the double layer ectopically grown MoS obtained in example 4 2 Optical microscopy of nanoplatelets. It can be seen from the figure that the method produces a small amount of ectopically grown MoS 2 But the majority of the area is connected to form a film. Namely MoS when the distance between two adjacent silicon chips is large 2 Of (2) feeding speedFast, many nucleation sites, so the sample is easy to be connected into a film.

Claims (9)

1. Ectopic nucleated double-layer MoS 2 Nanoplatelets characterized by the ectopically nucleated bilayer MoS 2 The nano sheet consists of an upper layer of MoS and a lower layer of MoS 2 Stacked with a top layer of MoS 2 Has nucleation sites deviated from the underlying MoS 2 The center position of (a).
2. Ectopic nucleation double-layer MoS 2 The preparation method of the nanosheet is characterized in that the method is to grow the double-layer MoS on the surface of the substrate in one step by utilizing chemical vapor deposition 2 Nanosheets, wherein in a quartz tube of a chemical vapor deposition apparatus, a substrate is placed above a molybdenum evaporation source with a horizontal inclination at an appropriate angle along the direction of gas flow.
3. The method according to claim 2, wherein the substrate is placed above the molybdenum evaporation source with an inclination of 1-3 °, and the substrate is SiO 2 The molybdenum evaporation source is molybdenum trioxide.
4. A producing method according to claim 2 or 3, characterized in that two or more substrates are stacked above the molybdenum evaporation source in the form of disturbed gas flow, and the vertical height between the adjacent substrates is about 3mm.
5. A method for preparing according to claim 2 or 3, characterized in that it comprises the steps of:
(1) Taking molybdenum trioxide powder as a molybdenum evaporation source, sodium chloride as a fluxing agent, taking elemental sulfur powder as a sulfur evaporation source, and sequentially placing the sulfur evaporation source, the molybdenum evaporation source and the substrate in a corresponding temperature interval in a quartz tube along the airflow direction;
(2) Mixing SiO 2 the/Si substrate is placed above the molybdenum evaporation source in a form of disturbed airflow;
(3) After the inert gas is used for discharging the air in the quartz tube, the tube type is heatedThe furnace is continuously filled with a proper amount of inert gas as carrier gas to finish MoS 2 And (4) growing the nanosheets.
6. The preparation method according to claim 5, wherein in the step (1), the corresponding temperature range of the molybdenum evaporation source is 650-720 ℃, preferably 680-700 ℃; the corresponding temperature range of the sulfur evaporation source is 170-220 ℃, and 190-200 ℃ is preferred; the SiO 2 The temperature range corresponding to the/Si substrate is 650-720 deg.C, preferably 680-700 deg.C.
7. The method according to claim 5, wherein the inert gas is argon gas, and the carrier gas flow is 10 to 50sccm, preferably 20 to 30sccm.
8. Ectopically nucleated bilayer MoS obtainable by the preparation process according to claims 2 to 7 2 Nanosheets characterized by an upper layer of MoS 2 The side length of the crystal grain is 2-5 mu m, and the lower layer MoS 2 The side length of the crystal grain is 3-15 mu m.
9. The ectopically nucleated dual-layer MoS according to claim 8 2 Nanosheets characterized in that the MoS 2 The crystal domains are approximately triangular or hexagonal.
CN202210992813.8A 2022-08-18 2022-08-18 Ectopic nucleation double-layer MoS 2 Nanosheet and preparation method thereof Pending CN115156524A (en)

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