A two-dimensional material lateral mosaic heterojunction array and its preparation and application

Abstract

The present invention belongs to the field of preparation of two-dimensional material heterojunction arrays, and specifically discloses a method for preparing a two-dimensional material lateral mosaic heterojunction array, obtaining a single crystal nanosheet of material A; sequentially performing laser etching and controllable thermal etching on the single crystal nanosheet of material A, and then regrowing material B to form a mosaic heterojunction array with clear boundaries composed of two-dimensional material A and two-dimensional material B. The present invention also provides a two-dimensional material lateral mosaic heterojunction array prepared by the preparation method and its application in the preparation of optoelectronic devices. The related heterojunction array prepared by the present invention has atomic-level smoothness, steep and flat heterojunction boundaries, almost no doping, and excellent optical and electrical properties of the material; this method provides a new material platform for large-scale functional two-dimensional material device integration, marking a key step in laying a solid material foundation for basic research and development of complex devices and two-dimensional heterostructure integrated circuits.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials, and in particular relates to a method for preparing a two-dimensional material transverse mosaic heterojunction array. Technical Background

[0002] Since the discovery of graphene in 2004, research on two-dimensional materials has been booming. Currently, two-dimensional materials and their heterostructures have become a hot material system that can be used to explore exotic physics and create new device functions at the limit of single-atom or few-atom thickness. [1-5] Typically, atomically thin two-dimensional sheets can be readily prepared by mechanical exfoliation of bulk layered crystals, and high-quality heterostructures can be obtained by highly versatile manual restacking methods. [6-8] On the one hand, these readily available two-dimensional materials and heterostructures have promoted the rapid development of basic research and basic devices, but on the other hand, they have also weakened the path to direct and controllable synthesis of two-dimensional materials and heterostructures to a certain extent. Previously, a large number of studies on two-dimensional materials were limited to mechanical exfoliation of materials and / or artificial stacking of heterostructures. The synthetic control of two-dimensional materials, especially the synthetic control of their heterostructures, has generally lagged behind.

[0003] Despite recent efforts in the synthesis and control of two-dimensional materials and their heterostructures [9-15] , but the stable growth of scalable two-dimensional heterostructure arrays remains a key challenge in the field. Because of the highly delicate nature of these atomically thin materials, it is still difficult to precisely control the nucleation and growth of atomically thin crystals. Current synthesis methods for two-dimensional crystals generally rely on the accidental nucleation of random defects on the growth substrate, with limited control over the spatial location, domain size and structure of the heterostructure. However, the current main processing methods (such as photolithography and focused ion beam technology) often leave undesirable residues or rough edge endpoints, which may act as uncontrolled nucleation sites, resulting in heterostructures with partially disordered interfaces or uncontrollable layer thickness. To date, the controlled growth of single crystal planar heterostructures with clean interfaces, clear manifestations of high comprehensive control and scalable integration has not been achieved.

[0004] [1]. Geim, Andre K., and Konstantin S. Novoselov. "The rise of graphene." Nanoscience and technology: a collection of reviews from nature journals. pp. 11-19 (2010).

[0005] [2].Lee,C.H.et al.Atomically thin p-n junctions with van der Waals heterointerfaces.Nat.Nanotechnol.9,676-681(2014).

[0006] [3].Tan,C.,Chen,J.,Wu,X.-J.&Zhang,H.Epitaxial growth of hybridnanostructures.Nat.Rev.Mater.3,1-13(2018).

[0007] [4].Radisavljevic,B.et al.Single-layer MoS2transistors.Nat.Nanotechnol.6,147(2011).

[0008] [5].Schaibley,J.R.et al.Valleytronics in 2Dmaterials.Nat.Rev.Mater.1,16055(2016).

[0009] [6].Wang,H.et al.Integrated circuits based on bilayer MoS2transistors.Nano Lett.12,4674-4680(2012).

[0010] [7].Wang,Q.H.et al.Electronics and optoelectronics of two-dimensionaltransition metal dichalcogenides.Nat.Nanotechnol.7,699(2012).

[0011] [8].Sangwan,V.K.et al.Gate-tunable memristive phenomena mediated bygrain boundaries in single-layer MoS2.Nat.Nanotechnol.10,403(2015).

[0012] [9].Zhou,J.et al.A library of atomically thin metalchalcogenides.Nature 556,355-359(2018).

[0013]

[10] .Shim,J.et al.Controlled crack propagation for atomic precisionhandling of wafer-scale two-dimensional materials.Science 362,665-670(2018).

[0014]

[11] .Wang,L.et al.Epitaxial growth of a 100-square-centimetre single-crystal hexagonal boron nitride monolayer on copper.Nature 570,91(2019).

[0015]

[12] .Najmaei,S.et al.Vapour phase growth and grain boundary structureof molybdenum disulphide atomic layers.Nat.Mater.12,754(2013).

[0016]

[13] .Zande,A.M.V.D.et al.Grains and grain boundaries in highlycrystalline monolayer molybdenum disulphide.Nat.Mater.12,554-561(2013).

[0017]

[14] .Huang,C.et al.Lateral heterojunctions within monolayer MoSe2-WSe2semiconductors.Nat.Mater.13,1096(2014).

[0018]

[15] .Gong,Y.et al.Vertical and in-plane heterostructures from WS2 / MoS2monolayers.Nat.Mater.13,1135(2014). Summary of the Invention

[0019] In order to overcome the common problems of existing arrayed heterojunction preparation methods such as unclean interface, uncontrollable growth site, and uncontrollable etching, the first purpose of the present invention is to provide a preparation method for a two-dimensional material lateral mosaic heterojunction array, aiming to improve the existing two-dimensional material arrayed heterojunction preparation method so that an atomic-level smooth, steep and flat boundary and low-doped two-dimensional material lateral mosaic heterojunction array can be obtained, and efficient, high-quality and scalable preparation can be achieved.

[0020] The second purpose of the present invention is to provide a two-dimensional material lateral mosaic heterojunction array material prepared by the preparation method.

[0021] The third object of the present invention is to provide an application of the prepared two-dimensional material lateral mosaic heterojunction array material in the preparation of optoelectronic devices and the obtained optoelectronic devices.

[0022] A method for preparing a two-dimensional material lateral mosaic heterojunction array comprises the following steps:

[0023] Step (a): obtaining a single crystal nanosheet of material A (also referred to as material A nanosheet in the present invention);

[0024] Step (b): laser etching the single crystal nanosheet of material A to obtain a nanosheet of material A with arrayed point defects;

[0025] Step (c): Covering the surface of the material A nanosheet with arrayed point defects in step (b) with a substrate material, and then thermally etching the surface at a temperature of 1000 to 1200° C. for 10 to 60 seconds; thermally etching the material A nanosheet with arrayed point defects into a material A nanosheet with a hole structure;

[0026] Step (d): epitaxially growing a heterojunction of material B in the hole region of the material A nanosheet prepared in step (c) to obtain an AB lateral mosaic heterojunction array;

[0027] The material A and the material B are independently selected from at least one of transition metal chalcogenides, halides, oxyhalides, carbides or nitrides, and A≠B.

[0028] The present invention combines laser etching with a thermal etching process under substrate coverage, further coordinated with the combined control of thermal etching temperature and time, enabling controlled thermal etching at laser-etched point defects and controllably inducing epitaxial growth of material B at the thermally etched sites, thereby forming a mosaic heterojunction. Furthermore, the present invention helps improve the morphology, structure, performance, and production efficiency of the resulting material. The present invention effectively addresses the common problems of arrayed heterojunction preparation methods, such as unclean interfaces and uncontrollable growth sites. The resulting mosaic heterojunction array exhibits atomically smooth, steep and flat heterojunction boundaries, virtually no doping, and excellent optical and electrical properties. This method provides a new material platform for large-scale functional two-dimensional material device integration, marking a key step in establishing a solid material foundation for the basic research and development of complex devices and two-dimensional heterostructure integrated circuits.

[0029] In the present invention, the single crystal nanosheet of material A can be any two-dimensional material of transition metal known in the industry.

[0030] Preferably, the material A is a sulfide or selenide of a transition metal;

[0031] Preferably, the transition metal is at least one of W and Mo;

[0032] In the present invention, the nanosheets of the material A can be obtained based on existing means. Preferably, the single crystal nanosheets of the material A can be obtained by CVD or PVD method;

[0033] Further preferably, the material A is WS2, and the growth conditions of the PVD single crystal nanosheets are: the growth temperature of WS2 is 1100℃-1250℃, preferably 1180℃-1200℃; the growth time is 1-10min, preferably 2-5min; the carrier gas flow rate is 30-350sccm, preferably 50-150sccm.

[0034] When material A is MoS2, the growth conditions of PVD single crystal nanosheets are: growth temperature of 1180°C-1200°C, growth time of 2-5 minutes; carrier gas flow rate of 90-300 sccm.

[0035] When material A is WSe2, the growth conditions of PVD single crystal nanosheets are: growth temperature of 1120℃-1180℃, growth time of 2-5min; carrier gas flow rate of 100-200sccm.

[0036] Preferably, during the preparation of the nanosheets of material A, the carrier gas is a protective gas; for example, it can be at least one of nitrogen and an inert gas, and the inert gas can be, for example, argon.

[0037] In the present invention, the nanosheets of material A are patterned and etched in advance by laser etching to obtain a target array.

[0038] In the present invention, array etching of nanosheets of material A can be achieved based on existing means.

[0039] Preferably, the laser etching is performed using a device for fixed-point laser irradiation;

[0040] Preferably, the device for fixed-point laser irradiation is a confocal Raman microscope;

[0041] The scanning program uses a Raman wireframe scanning mode. In the present invention, the spacing of point defects can be effectively controlled by changing the step size of the Raman wireframe scanning mode, thereby producing material A nanosheets with point defect arrays of different periods.

[0042] Preferably, a raster scanning focused laser is used to irradiate the nanosheet of material A to form a periodic local defect array. Preferably, in step (b), the wavelength of the laser is 355 to 633 nm; preferably 480 to 500 nm;

[0043] Preferably, the power of the laser is 10 to 50 mW; preferably 20 to 30 mW;

[0044] Preferably, the laser single point irradiation time is 1 to 10 seconds; preferably 5 to 8 seconds;

[0045] Preferably, the spacing between each dot is 5 to 20 μm, more preferably 10 to 15 μm.

[0046] In the present invention, pre-laser etching, coupled with subsequent thermal etching under substrate coverage, enables controlled thermal etching of microcavities within confinement. This not only allows the point defects of the arrayed point defects in the nanosheets of Material A to be precisely and controllably thermally etched into well-structured pores, but also unexpectedly induces the controlled lateral epitaxial growth of Material B in the thermally etched region, forming a mosaic heterojunction array with clear boundaries and well-defined morphology. The present invention utilizes laser irradiation and thermal etching methods, avoiding the use of a mask and photoresist (PMMA). This effectively addresses the difficulty in controlling nucleation at the boundaries during the growth of lateral mosaic heterojunction arrays of two-dimensional materials, achieving atomic-level flatness at the boundaries. This preparation method offers advantages such as a simple operational process and good experimental reproducibility.

[0047] In the present invention, the substrate is a planar material that can exist stably at thermal etching temperature.

[0048] Preferably, the substrate is at least one of a silicon / silicon dioxide substrate, a pure silicon wafer, a silicon nitride substrate, a sapphire substrate or a mica substrate.

[0049] In the present invention, in step (c), a substrate is covered on the surface of the nanosheets of material A with arrayed point defects, a microcavity is formed at each point defect, and then thermal etching is performed.

[0050] The atmosphere of the thermal etching is a protective gas, more preferably at least one of nitrogen and Ar.

[0051] Preferably, the temperature of the thermal etching is 1000-1150°C, more preferably 1050-1100°C.

[0052] Preferably, the holding time for etching at the thermal etching temperature is 20 to 40 seconds, and more preferably 25 to 30 seconds.

[0053] In the present invention, the combination of laser etching, controllable thermal etching and thermal etching process conditions can induce the growth of material B nanosheets, which is conducive to obtaining the mosaic heterojunction array.

[0054] In the present invention, the material B is any two-dimensional material that can form a heterojunction with the material A.

[0055] Preferably, in step (d), the material B is a sulfide or selenide of a transition metal;

[0056] Preferably, the transition metal is at least one of W and Mo;

[0057] The two-dimensional material of material B can be prepared based on existing means, for example, single crystal nanosheets of material B can be obtained by CVD or PVD method.

[0058] Preferably, a gas-changing method is used to epitaxially grow a heterojunction of material B in the hole region of the nanosheet of material A by a PVD method;

[0059] The gas change means refers to using reverse carrier gas flow before heating material B to the growth temperature, and changing to forward carrier gas flow when the temperature reaches the growth temperature;

[0060] The reverse carrier gas flow refers to the direction from the nanosheets of material A to the nanosheets of material B.

[0061] Preferably, the material B is WS2, and the growth conditions are: growth temperature of 1180°C-1200°C, growth time of 2-5 minutes, and forward carrier gas flow rate of 50-350 sccm;

[0062] When material B is MoS2, the growth conditions are: growth temperature is 1100℃-1200℃, preferably 1180℃-1200℃; growth time is 1-10min, preferably 2-5min; forward carrier gas flow rate is 30-350sccm, preferably 90-300sccm.

[0063] When material B is WSe2, the growth conditions are: growth temperature is 1100℃-1200℃, preferably 1120℃-1180℃; growth time is 1-10min, preferably 2-5min; forward carrier gas flow rate is 30-350sccm, preferably 100-200sccm.

[0064] Preferably, the carrier gas during the growth stage of material B is a protective gas, such as at least one of nitrogen and an inert gas.

[0065] In the present invention, there is no particular requirement for the flow rate of the reverse carrier gas. For example, it may be greater than or equal to 10 sccm, preferably 100 to 400 sccm.

[0066] In the present invention, material B and material A are selected from different materials; the material A is WS2; and the material B is MoS2 or WSe2.

[0067] The preferred method for preparing a two-dimensional material lateral mosaic heterojunction array of the present invention comprises the following steps:

[0068] Step (a): Chemical vapor deposition of material A powder onto a silicon / silicon dioxide substrate to form single-crystalline nanosheets of material A; material A is selected from WS2. The WS2 growth temperature is 1100°C-1250°C, preferably 1180°C-1200°C; the growth time is 1-10 minutes, preferably 2-5 minutes; and the carrier gas flow rate is 30-350 sccm, preferably 50-350 sccm.

[0069] Step (b): Targeted laser irradiation is performed on a nanosheet of material A to produce a nanosheet of material A with arrayed point defects. Step (b) is performed using a confocal Raman microscope laser as the laser source to create a point defect array at specific locations on material A. The spacing of the point defects can be effectively controlled by varying the step size of the Raman wireframe scanning mode. Nanosheets of material A with point defect arrays of varying periods are produced.

[0070] Step (c): Thermally etch the nanosheets of Material A with arrayed point defects into nanosheets of Material A with a pore structure; in step (c), thermal etching is performed using a microcavity confinement method (i.e., the substrate on which the nanosheets of Material A with the point defect array have been grown is placed face-up, and a new substrate is placed on top of it). The gas atmosphere in step (c) is high-purity argon, the thermal etching temperature is 1000-1100°C, and the thermal etching time is 20s-35s. The substrate is a Si / SiO2 substrate, a sapphire substrate, or a mica substrate; more preferably, a Si / 285nmSiO2 substrate.

[0071] Step (d): Using material B powder as a raw material, epitaxially grow material B heterojunctions in the pore region to obtain a lateral mosaic heterojunction array. In step (d), using material B powder as a raw material, epitaxial growth is performed in the pores of material A nanosheets having a pore structure to obtain a finished product of a 2D material lateral mosaic heterojunction array, wherein the B powder is solely selected from MoS2 or WSe2. The growth temperature of MoS2 is 1100°C-1200°C, preferably 1180°C-1200°C; the growth time is 1-10 minutes, preferably 2-5 minutes; the forward carrier gas flow rate is 30-350 sccm, preferably 90-300 sccm; the growth temperature of WSe2 is 1100°C-1200°C, preferably 1120°C-1180°C; the growth time is 1-10 minutes, preferably 2-5 minutes; the forward carrier gas flow rate is 30-350 sccm, preferably 100-200 sccm.

[0072] The method of the present invention, wherein the deposition device for implementing the material growth and epitaxial growth in the mosaic heterojunction array includes a quartz tube, the central chamber of the quartz tube is a high-temperature constant temperature zone, the raw material powder of the two-dimensional material is placed in the high-temperature constant temperature zone, and the device is further provided with a heating device for heating the high-temperature constant temperature zone; the chamber at one end of the quartz tube is a variable temperature deposition zone, and the substrate or the substrate deposited with the two-dimensional material is placed in the variable temperature deposition zone;

[0073] Both ends of the quartz tube are provided with air holes, the air hole close to the base end is air hole 1, and the air hole at the opposite end of air hole 1 is air hole 2.

[0074] The variable temperature deposition zone is arranged on one side of the high temperature constant temperature zone and is either not equipped with a heating device or is equipped with one.

[0075] In the present invention, in step (a), the preparation process of the nanosheets of material A is as follows: first, a carrier gas is introduced from pore 2 and discharged from pore 1 (positive airflow), and the pipeline is cleaned; then, the powder of the two-dimensional material A is loaded into an alumina boat and placed in a high-temperature constant temperature area; the substrate material is placed in a variable temperature deposition area; under the continuous purge of the carrier gas, the powder of the two-dimensional material A is continuously heated in the high-temperature constant temperature area, and after heating to the growth temperature, it is deposited on the surface of the substrate to obtain nanosheets of material A.

[0076] In step (d) of the present invention, material B is placed upstream (close to the side of pore 2, high temperature constant temperature zone), and the material obtained in step (c) is used as a substrate and placed downstream (close to the side of pore 1, variable temperature deposition zone). Material B is heated, and before the temperature is raised to the growth temperature, a reverse carrier gas is used (pore 1 is the carrier gas inlet, and pore 2 is the carrier gas outlet); after the temperature reaches the growth temperature, it is changed to a forward carrier gas flow (pore 2 is the carrier gas inlet, and pore 1 is the carrier gas outlet) to perform controllable epitaxial growth to obtain the mosaic heterojunction array.

[0077] A more preferred method for preparing a two-dimensional material lateral mosaic heterojunction array of the present invention comprises the following steps:

[0078] Step (1): The powder source of material A is loaded into an alumina boat and placed in the middle high-temperature constant temperature area of ​​a quartz tube (2 cm diameter) of a tube furnace; a silicon oxide wafer (Si / 285 nm SiO2) is placed in the variable temperature deposition area of ​​the tube furnace as a substrate for material deposition; the material A is WS2;

[0079] Argon gas is first passed through the pipeline for cleaning (the flow rate of argon is, for example, 300 sccm, and the flow time is, for example, 20 minutes). Argon gas is used as a carrier gas during the heating process. The growth temperature of WS2 is 1180°C-1200°C, the growth time is 2-5 minutes, and the carrier gas flow rate is 50-350 sccm.

[0080] After the deposition is completed, a single-layer single-crystal WS2 nanosheet will be deposited on the substrate surface;

[0081] Step (2): Place the material A nanosheet under the Raman microscope lens, perform Raman wireframe scanning, and prepare a point defect array on the material A nanosheet.

[0082] Step (3): thermally etching the material A nanosheet having a point defect array to obtain a material A nanosheet having a hole structure.

[0083] Step (4): Preparation of a lateral mosaic heterojunction array of two-dimensional materials (e.g., WS2-WSe2, WS2-MoS2), comprising the following steps:

[0084] The raw material powder of the two-dimensional material for lateral epitaxy (material B) is loaded into an alumina boat and placed in the middle high-temperature area of ​​a horizontal tube furnace quartz tube (2 cm diameter); the raw material of the material B is WSe2 or MoS2; the materials B and A are different materials;

[0085] Placing the substrate of the nanosheet of material A having a porous structure prepared in step (3) in the variable temperature deposition area of ​​the downstream tube furnace;

[0086] First, argon gas is passed through the pipeline (the flow rate of argon is, for example, 300 sccm, and the introduction time is, for example, 20 minutes). During the reaction temperature rise stage, a reverse gas flow is introduced (pore 1 leads to pore 2, wherein the flow rate of Ar is preferably 300 sccm). When the growth temperature of the two-dimensional raw material for lateral inward and outward extension is reached, a forward gas flow is introduced (pore 2 leads to pore 1). Different types of two-dimensional materials for lateral inward and outward extension use different carrier gas flow rates, growth temperatures, and growth times.

[0087] The growth temperature of WSe2 is 1120℃-1180℃, the growth time is 2-5min; the forward carrier gas flow rate is 100-200sccm; the growth temperature of MoS2 is 1180℃-1200℃, the growth time is 2-5min; the forward carrier gas flow rate is 90-300sccm.

[0088] The present invention also includes a two-dimensional material transverse mosaic heterojunction array prepared by the preparation method. Nanosheets of material B with clear boundaries grow at the laser-etched and controllable thermal-etched areas of material A, forming a mosaic heterojunction array formed by materials A and B. The mosaic heterojunction is a mosaic heterojunction, which forms an arrayed heterostructure (such as) of material B (the shape is the same as the first material, and the size is proportionally reduced) inside material A. Figure 6 (as shown in (a)).

[0089] The present invention also includes the application of the two-dimensional material lateral mosaic heterojunction array prepared by the preparation method, and the lateral heterostructure material is used to prepare new micro-nano electronic components and new two-dimensional structures such as pn junction diodes, photovoltaic devices, photodetectors, light-emitting diodes, laser diodes, quantum well devices, as well as pnp transistors, inverters and photonic crystals.

[0090] The methods for preparing the optical and electrical components can refer to the prior art.

[0091] The present invention also provides a photoelectric device comprising a two-dimensional material lateral mosaic heterojunction array prepared by the preparation method of the present invention;

[0092] In the present invention, the photoelectric device is at least one of a pn junction diode, a photovoltaic device, a photodetector, a light emitting diode, a laser diode, a quantum well device, a pnp transistor, an inverter, and a photonic crystal.

[0093] Beneficial effects

[0094] The present invention, through the combination of the laser etching and controllable thermal etching, further coordinated with the joint control of thermal etching means, temperature and other parameters, can unexpectedly achieve synergy and controllable etching. Not only that, it can also unexpectedly induce the controllable growth of two-dimensional materials to form mosaic heterojunction array materials, and can also improve the problem of unclear boundaries of heterojunction materials, effectively improving the morphology, results and performance of the materials.

[0095] The overall experimental process of the present invention is simple and the operation is highly accurate, which can greatly improve the efficiency of preparing related materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 Schematic diagram of laser irradiation of materials using a confocal Raman microscope;

[0097] Figure 2 Figure 2 is a side view of WS2 with a point defect array after laser irradiation, where (a) is the atomic force height map of the point defect array, (b) is the magnified atomic force height image of one point, and (c) is the atomic force phase map of the point defect array.

[0098] Figure 3 Schematic diagrams of a thermal etching device, a microcavity formation device, and a PVD system, wherein (a) is a schematic diagram of the thermal etching device, and (b) is a schematic diagram of a tube furnace of the PVD system;

[0099] Figure 4 These are optical images of WS2 with a hole structure at different thermal etching times in step (3) of Example 1, wherein (a) is an optical image of WS2 with a hole structure after 20 s, (b) is an optical image of WS2 with a hole structure after 25 s, (c) is an optical image of WS2 with a hole structure after 30 s, and (d) is an optical image of WS2 with a hole structure after 35 s;

[0100] Figure 5 These are test images of WS2 with a hole structure after thermal etching for 30 seconds in step (3) of Example 1, where (a) is an atomic force image, (b) is a Raman mapping, and (c) is a photoluminescence mapping;

[0101] Figure 6 The test images of the epitaxial WS2-WSe2 mosaic heterojunction array in Example 1, where (a) is an optical microscope image, (b) is an atomic force phase diagram, and (c) is an atomic force height diagram;

[0102] Figure 7 Raman mapping of the epitaxial WS2-WSe2 mosaic heterojunction array in Example 1;

[0103] Figure 8 Photoluminescence mapping of the epitaxial WS2-WSe2 mosaic heterojunction array in Example 1;

[0104] Figure 9 These are test images of the epitaxial WS2-MoS2 mosaic heterojunction array in Example 2, where (a) is an optical microscope image, (b) is an atomic force phase diagram, and (c) is an atomic force height diagram;

[0105] Figure 10 Raman mapping of the epitaxial WS2-MoS2 mosaic heterojunction array in Example 2;

[0106] Figure 11Photoluminescence mapping of the epitaxial WS2-MoS2 mosaic heterojunction array in Example 2;

[0107] Figure 12 Statistical graphs of thermal etching time and temperature versus hole size. (a) and (b) show the relationship between etching time and hole size, and (c) shows the relationship between etching temperature and hole size.

[0108] Figure 13 For device test pictures. Among them, (a) device optical picture, (b) is I DS -V DS Curve (c) is I DS -V DS Semi-logarithmic plot of the curve.

[0109] Figure 14 This is an optical image of WS2 with a hole structure prepared in Comparative Example 1;

[0110] Figure 15 This is an optical image of the epitaxial WS2-WSe2 mosaic heterojunction array prepared in Comparative Example 2; DETAILED DESCRIPTION

[0111] The present invention is further described below through examples of implementation, but the content of the present invention is not limited to the following content.

[0112] Example 1

[0113] A two-dimensional material lateral mosaic heterojunction array and a preparation method thereof, wherein the specific implementation steps are as follows:

[0114] (1) Preparation of two-dimensional material heterojunction single crystal material WS2, including the following steps:

[0115] 0.6g of WS2 powder source was weighed and loaded into an alumina boat, which was placed in the middle high-temperature zone of a quartz tube (2cm diameter) in a tube furnace. A silicon oxide wafer (Si / 285nm SiO2) was placed in the variable temperature deposition zone of the tube furnace as a substrate for material deposition.

[0116] 300 sccm argon gas was first passed through for 20 minutes to clean the pipeline. Argon gas was used as the carrier gas during the heating process with a gas flow rate of 80 sccm. The temperature was raised to the growth temperature of the growth temperature-related material of 1200°C. After a growth time of 3 minutes, a single-layer single-crystal WS2 nanosheet deposited on silicon oxide was obtained.

[0117] (2) Laser irradiation to produce a point defect array, comprising the following steps:

[0118] The single-layer single-crystal WS2 nanosheet obtained in (1) was placed under the lens of a confocal Raman microscope, and the single-layer WS2 nanosheet was irradiated in a wireframe scanning mode using a focused laser (488 nm, 20 mW). The single-point irradiation time was 5 s, forming a periodic local defect array with a spacing of 10 μm.

[0119] (3) Controllable thermal etching to prepare the hole structure, including the following steps:

[0120] The sample with the point defect array obtained in (2) was covered with another substrate (Si / 285nmSiO2) to form a microcavity, and then placed in a high-purity argon atmosphere at 1100℃. Anisotropic thermal etching of the sample near the laser-etched area produced a periodic array of triangular holes. The optical images of different processing times are shown in Figure 4 ; Select the material that is thermally etched for 30 seconds to proceed to the following steps:

[0121] (4) Preparation of a two-dimensional material lateral mosaic heterojunction array WS2-WSe2, comprising the following steps:

[0122] 0.6 g of two-dimensional material powder WSe2 for lateral in- and out-epitaxialization was loaded into an alumina boat and placed in the middle high-temperature area of ​​a horizontal tubular furnace quartz tube (2 cm diameter).

[0123] The WS2 substrate with a porous structure prepared in step (3) is placed in the variable temperature deposition area of ​​the downstream tube furnace.

[0124] Initially, 300 sccm of argon was passed through the pipeline for 20 minutes to purge the system. During the reaction temperature rise phase, a reverse gas flow (Ar 300 sccm, from substrate to source material) was introduced. When the epitaxial growth temperature of the material was reached, a forward gas flow was introduced. After growth was complete, a reverse gas flow was introduced again to terminate the reaction, resulting in a corresponding WS2-WSe2 lateral mosaic heterojunction array. The corresponding growth temperature was WSe2 (1150°C), the growth time was WSe2 (2 minutes), and the forward gas flow rate of Ar was WSe2 (100 sccm).

[0125] Figure 6-8 To prepare optical images, atomic force images, Raman mapping, and fluorescence mapping of the samples, it was confirmed that the obtained samples were free of doping and had excellent performance indicators. Figure 6-8 All scale bars are 5 μm.

[0126] Example 2

[0127] Compared with Example 1, the only difference is that in step (4), the two-dimensional material powder used for lateral epitaxy is MoS2 (that is, MoS2 powder is used instead of WSe2 powder in step (4) of Example 1); the growth temperature of MoS2 is 1180°C, the growth time is 2 minutes, and the forward gas flow rate of Ar during the growth process is 120 sccm. A two-dimensional material lateral mosaic heterojunction array WS2-MoS2 is produced.

[0128] Figure 9-11 To prepare optical images, atomic force images, Raman mapping, and fluorescence mapping of the samples, it was confirmed that the obtained samples were free of doping and had excellent performance indicators. Figure 9-11 All scale bars are 10 μm.

[0129] Example 3

[0130] The thermal etching time and thermal etching temperature of step (3) of Example 1 were compared. That is, the relationship between etching time and hole size was discussed while controlling the same etching problem. The relationship between etching temperature and hole size was discussed while controlling the same etching time.

[0131] Figure 12 The figure shows the relationship between thermal etching time, thermal etching temperature and hole size. The relationship between etching time, etching temperature and hole size is linear.

[0132] Example 4

[0133] Device preparation steps: First, two layers of PMMA were suspended on the substrate with the mosaic heterojunction (prepared in Example 1), then the electrode pattern was exposed using EBL, followed by evaporation of 50 nm thick gold as the electrode, and finally the corresponding data was collected using a probe station.

[0134] Semiconductor device testing was performed on mosaic heterojunction arrays. DS -V DS curve and rectification ratio. Figure 13 The device test diagram shows the diode characteristics at different back gate voltages. The semi-logarithmic diagram shows 10 -6 The rectification ratio.

[0135] Comparative Example 1

[0136] Compared with Example 1, the only difference is that in step (3), no substrate is covered on the sample with the point defect array in (2).

[0137] The obtained WS2 with hole structure not only undergoes thermal etching in the laser irradiated area, but also produces a large amount of random thermal etching in the laser non-irradiated area, such as Figure 14 shown. Figure 14 The scale bar is 10 μm.

[0138] Comparative Example 2

[0139] Compared with Example 1, the difference is that step (2) and step (3) are replaced, and point defects are produced by conventional photolithography technology and then oxygen plasma etching is selected.

[0140] That is, in step (2), photolithography is used instead of laser irradiation. First, a layer of photoresist is suspended on the substrate on which material A has been grown. Then, a dot matrix mask with a spacing of 10 μm and a size of 1 μm is placed on the substrate. Finally, the nanosheets of material A with a 1-2 μm dot defect array are obtained by photolithography and development under ultraviolet light. The photoresist used here is BP121 general-purpose positive photoresist; the mask used here is a chromium metal mask.

[0141] In step (3), oxygen plasma etching is used instead of high-temperature thermal etching. The material A nanosheet having a 1-2 μm point defect array is placed in a plasma etcher. Oxygen is introduced into the etcher to form an oxygen plasma multi-material A nanosheet. The etching time is 60 seconds to obtain a material A nanosheet having a porous structure. Finally, acetone is used to remove the remaining photoresist on the material A nanosheet and the substrate.

[0142] The residual glue introduced by this method cannot be removed, resulting in the epitaxial formation of thick WSe2 with polycrystalline domains, such as Figure 15 shown. Figure 15 The scale bar is 10 μm.

Claims

1. A method for preparing a two-dimensional material lateral mosaic heterojunction array, characterized in that: The following steps are involved: Step (a): obtaining single crystal nanosheets of material A; Step (b): laser etching the single crystal nanosheet of material A to obtain nanosheets of material A with arrayed point defects; the material A is a sulfide or selenide of a transition metal; the transition metal is at least one of W and Mo; Step (c): Covering the surface of the material A nanosheets with arrayed point defects in step (b) with a substrate material, and then thermally etching at a temperature of 1000-1200°C for 10-60 seconds; Thermally etching the material A nanosheet with arrayed point defects into a material A nanosheet with a hole structure; The atmosphere of thermal etching is protective gas; Step (d): epitaxially growing a heterojunction of material B in the hole region of the nanosheet of material A prepared in step (c) to obtain an AB lateral mosaic heterojunction array; The material B is a sulfide or selenide of a transition metal; the transition metal is at least one of W and Mo; and A≠B.

2. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, characterized in that: In step (a), single crystal nanosheets of material A are obtained by CVD or PVD method.

3. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 2, characterized in that: In step (a), the material A is WS2, and the growth conditions of the PVD single crystal nanosheets are: the growth temperature of WS2 is 1100°C-1250°C; the growth time is 1-10 min; and the carrier gas flow rate is 30-350 sccm.

4. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 3, characterized in that: In step (a), the material A is WS2, and the growth conditions of the PVD single crystal nanosheets are: the growth temperature of WS2 is 1180°C-1200°C; the growth time is 2-5 minutes; and the carrier gas flow rate is 50-150 sccm.

5. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 2, wherein: When material A is MoS2, the growth conditions of PVD single crystal nanosheets are: growth temperature of 1180℃-1200℃, growth time of 2-5min; carrier gas flow rate of 90-300sccm; When material A is WSe2, the growth conditions of PVD single crystal nanosheets are: growth temperature of 1120℃-1180℃, growth time of 2-5min; carrier gas flow rate of 100-200sccm.

6. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 3, characterized in that: The carrier gas is protective gas.

7. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, characterized in that: The laser etching is performed using a device for fixed-point laser irradiation.

8. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 7, characterized in that: The device for the fixed-point laser irradiation is a confocal Raman microscope.

9. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 7, characterized in that: Raster scanning is used to focus laser irradiation on the nanosheet of material A to form a periodic array of local defects.

10. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, wherein: In step (b), the wavelength of the laser is 355-633 nm; The laser power is 10~50 mW; The laser single point irradiation time is 1~10s; The spacing between each point is 5~20 μm.

11. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 10, wherein: In step (b), the wavelength of the laser is 480-500 nm; The power of the laser is 20~30mw; The laser single point irradiation time is 5~8s; The spacing between each point is 10~15μm.

12. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, wherein: In step (c), the substrate is a planar material that can exist stably at thermal etching temperature.

13. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, wherein: The substrate is at least one of a silicon / silicon dioxide substrate, a pure silicon wafer, a silicon nitride substrate, a sapphire substrate or a mica substrate.

14. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, wherein: The substrate is covered on the surface of the material A nanosheet with arrayed point defects, and microcavities are formed at the defects, followed by thermal etching.

15. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 1, wherein: Single-crystalline nanosheets of material B were obtained by CVD or PVD method.

16. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 15, characterized in that: Using a gas-changing method, a PVD method is used to epitaxially grow a heterojunction of material B in the hole area of ​​the material A nanosheet; The gas change means refers to using reverse carrier gas flow before heating material B to the growth temperature, and changing to forward carrier gas flow when the temperature reaches the growth temperature; The reverse carrier gas flow refers to the direction from the nanosheets of material A to the nanosheets of material B.

17. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 16, wherein: The material B is WS2, and the growth conditions are: growth temperature of 1180°C-1200°C, growth time of 2-5 minutes, and forward carrier gas flow rate of 50-350 sccm; When material B is MoS2, the growth conditions are: growth temperature of 1100°C-1200°C; growth time of 1-10 min; forward carrier gas flow rate of 30-350 sccm; When material B is WSe2, the growth conditions are: growth temperature is 1100°C-1200°C; growth time is 1-10 min; and forward carrier gas flow rate is 30-350 sccm.

18. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 17, wherein: When material B is MoS2, the growth conditions are: growth temperature 1180℃-1200℃; growth time 2-5min; forward carrier gas flow rate 90-300sccm; When material B is WSe2, the growth conditions are: growth temperature is 1120°C-1180°C; growth time is 2-5 minutes; and forward carrier gas flow rate is 100-200 sccm.

19. The method for preparing a two-dimensional material lateral mosaic heterojunction array according to claim 16, wherein: The carrier gas is protective gas; The flow rate of the reverse carrier gas is greater than or equal to 10 sccm; The A is WS2; the B is MoS2 or WSe2.

20. A two-dimensional material lateral mosaic heterojunction array prepared by the preparation method according to any one of claims 1 to 19.

21. An application of the two-dimensional material lateral mosaic heterojunction array according to claim 20, characterized in that: It is used to prepare optoelectronic devices.

22. The use of the two-dimensional material lateral mosaic heterojunction array according to claim 21, characterized in that: The invention can be used to prepare at least one of a pn junction diode, a photovoltaic device, a photodetector, a light emitting diode, a laser diode, a quantum well device, a pnp triode, an inverter and a photonic crystal.

23. A photoelectric device, characterized in that: Contains the two-dimensional material lateral mosaic heterojunction array as described in claim 20.

24. The optoelectronic device according to claim 23, wherein The photoelectric device is at least one of a pn junction diode, a photovoltaic device, a photodetector, a light emitting diode, a laser diode, a quantum well device, a pnp transistor, an inverter, and a photonic crystal.

Images