A two-dimensional transition metal chalcogenide and its preparation and application

Abstract

The present invention relates to a two-dimensional transition metal chalcogenide compound and its preparation and application. Chalcogenide element and transition metal element are used as target sources, and vapor deposition is performed on a substrate by molecular beam epitaxy technology combined with step evaporation and post-evaporation strategies, thereby obtaining a high-quality, large-size two-dimensional transition metal chalcogenide compound thin film material. Compared with the prior art, the film morphology prepared by the present invention is a few-layer planar structure, a multi-layer nanorod structure or a multi-layer nanotube structure. The whole method is simple, efficient, and has high product quality. It has great application prospects in the fields of high-performance micro-nano devices, field effect transistors, photoelectric detection, and integrated circuits.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional semiconductor materials and relates to a two-dimensional transition metal sulfide compound and its preparation and application. Background Art

[0002] Photodetectors play an important role in converting optical signals into electrical signals in optical communication systems. The ability to achieve wide-spectrum integrated photodetection is crucial to improving the upgrade capabilities of modern communication and sensing systems in security, environmental monitoring, optical communications, etc.

[0003] Two-dimensional transition metal chalcogenide photodetectors have a high response rate in the spectral range from infrared light to ultraviolet light and terahertz. At present, the methods for preparing two-dimensional transition metal chalcogenides are mainly mechanical exfoliation, laser thinning, chemical vapor deposition, etc. However, it is still a challenge to prepare high-quality, large-area controllable two-dimensional transition metal chalcogenides, which also brings great difficulties to the application of two-dimensional transition metal chalcogenides in the field of photoelectric detection. Summary of the invention

[0004] The purpose of the present invention is to provide a two-dimensional transition metal sulfide compound and its preparation and application.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the technical solutions of the present invention provides a method for preparing a two-dimensional transition metal chalcogenide, comprising the following steps:

[0007] (1) cleaning and annealing the substrate to obtain an atomically flat surface;

[0008] (2) fixing the substrate processed in step (1) on a base and placing it in a cavity of a molecular beam epitaxy device;

[0009] (3) setting a first beam source furnace whose target source is a chalcogenide element and a second beam source furnace whose target source is a transition metal element, firstly evaporating the transition metal element in the second beam source furnace by heating, and depositing on the substrate to form a transition metal element thin film, and then heating the chalcogenide element in the first beam source furnace, and continuing to deposit, to obtain a composite thin film;

[0010] (4) The obtained composite film is annealed to complete the process.

[0011] Furthermore, the substrate is selected as a silicon wafer <100> ,silver <111> , sapphire, mica flakes, silicon carbide, gallium arsenide, graphene or highly oriented pyrolytic graphite.

[0012] Furthermore, the chalcogen element may be sulfur (S), selenium (Se) or tellurium (Te).

[0013] Furthermore, the transition metal element may be tungsten (W), vanadium (V), molybdenum (Mo), niobium (Nb), platinum (Pt) or palladium (Pd).

[0014] Furthermore, in step (2), the substrate temperature in the molecular beam epitaxy equipment is 25 to 800°C, and the vacuum degree of the body is 10 -7 ~10 -10 pa.

[0015] Furthermore, in step (2), the substrate is also rotated at a rotation speed of 0 to 20 rad / min. Here, when the rotation speed is 0, it means that the substrate does not rotate. Preferably, the rotation speed is not 0.

[0016] Furthermore, in step (3), the temperatures of the second beam source furnace and the first beam source furnace during the evaporation deposition process are independently 50 to 2000°C.

[0017] Furthermore, in step (3), the deposition rates of the transition metal element in the second beam source furnace and the chalcogen element in the first beam source furnace are independently The deposition time is independently 1 to 1000 min.

[0018] Furthermore, the composite film obtained in step (3) is further subjected to post-evaporation treatment under the condition of heating in the first beam source furnace. The substrate temperature during post-evaporation is 100-800°C.

[0019] Furthermore, in the post-evaporation process, the temperature of the first beam source furnace during the evaporation deposition process is 50-2000°C, and the deposition rate of the chalcogenide element in the first beam source furnace is The deposition time is 0 to 200 minutes. When the post-evaporation treatment time is 0, it means that there is no post-evaporation treatment process. Preferably, the post-evaporation treatment time is not 0.

[0020] Furthermore, in step (4), the annealing treatment temperature is 25 to 500° C. and the time is 0 to 48 hours.

[0021] The second technical solution of the present invention provides a two-dimensional transition metal chalcogenide compound, which is prepared by the preparation method described above. Based on the Kirkendall effect, the diffusion speeds of transition metal element gas and chalcogen element gas on the film surface are different, and the reaction process and defect degree are adjusted to obtain a two-dimensional transition metal chalcogenide compound with a few-layer planar structure, a multi-layer nanorod structure or a multi-layer nanotube structure.

[0022] A third technical solution of the present invention provides an application of a two-dimensional transition metal chalcogenide compound, which is used in the field of photoelectric detectors.

[0023] Molecular beam epitaxy is a dynamic process, that is, the neutral particles (atoms or molecules) evaporated by heat are deposited and adsorbed on the heated substrate. The adsorbed atoms or molecules migrate and decompose on the substrate surface and fuse into the lattice of the substrate or epitaxial layer. The molecules or atoms that fail to enter the lattice leave the surface due to thermal desorption. Molecular beam epitaxy technology can be used to obtain large-area high-quality two-dimensional materials.

[0024] The two-dimensional transition metal chalcogenide compound of the present invention has unique electronic, optical and energy band properties and good stability in the air. It can be assembled into a field effect transistor and applied in the field of photodetectors.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) Molecular beam epitaxy technology has the advantage of low growth rate, and can precisely control thickness, structure and composition, which is conducive to the growth of superlattice materials and epitaxial thin film materials. At the same time, the substrate temperature of molecular beam epitaxy technology is low, which reduces the lattice mismatch effect caused by interface thermal expansion and the influence of substrate impurities on the self-doping diffusion of the epitaxial layer. Molecular beam epitaxy technology can be used to obtain large-area thin film materials with good surface morphology, good uniformity, purity and integrity;

[0027] (2) The step evaporation method first epitaxially grows a large area of ​​continuous transition metal element B on the substrate. The evaporated chalcogen element A can react with the element B on the substrate and insert into the chemical bond of the element B. The post-evaporation method can adjust the atomic ratio of A and B in the thin film material; the present invention controls the process of step evaporation and post-evaporation, utilizes the Kirkendall effect, adjusts the reaction process and the degree of defects, and obtains a few-layer planar structure, a multi-layer nanorod structure or a multi-layer nanotube structure.

[0028] (3) The present invention is simple, efficient, and has high product quality. The prepared thin film can reach the inch level and is compatible with the traditional silicon-based CMOS process, fully meeting the application requirements of large-scale device integration.

[0029] (4) The two-dimensional transition metal chalcogenide photodetector of the present invention has a significant photocurrent on / off ratio and a fast response time, and has great application prospects in multispectral detection and imaging in the fields of civil, military, criminal investigation, and medical treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a molecular beam epitaxy device provided by the present invention;

[0031] Figure 2 It is a schematic diagram of the preparation process of two-dimensional transition metal sulfide compounds provided by the present invention.

[0032] Figure 3 It is a scanning electron microscope image of a two-dimensional transition metal chalcogenide compound of a multilayer nanorod structure prepared in Example 1 and a multilayer nanotube structure prepared in Example 5 provided by the present invention.

[0033] Figure 4 It is the ultraviolet photoelectron energy spectrum and surface potential of the two-dimensional transition metal chalcogenide compound with multilayer nanotube structure prepared in Example 5 provided by the present invention.

[0034] Figure 5 It is a schematic structural diagram of a back-gate field effect transistor photodetector provided by the present invention.

[0035] Description of the markings in the figure:

[0036] 1. Vacuum chamber; 2. Rotation axis; 3. Base; 4. Substrate; 5. First beam source furnace; 6. Second beam source furnace; 7. Support frame; 8. Transition metal single substance layer; 9. Transition metal chalcogenide layer; 10. Silicon dioxide / silicon substrate; 11. Source; 12. Drain; 13. Light source. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0038] The present invention provides a method for preparing a two-dimensional transition metal chalcogenide compound, which is carried out in a molecular beam epitaxy device, such as Figure 1 The molecular beam epitaxy equipment includes a vacuum chamber 1, a base 3 arranged at the top of the vacuum chamber 1 through a rotating shaft 2, and two beam source furnaces are arranged at the bottom of the vacuum chamber 1, namely a first beam source furnace 5 whose target source is a chalcogen element and a second beam source furnace 6 whose target source is a transition metal element. During deposition preparation, a substrate 4 is fixedly placed on the base 3.

[0039] In addition, based on the above molecular beam epitaxy equipment, the present invention can adopt the following two preparation methods, specifically refer to Figure 2 As shown:

[0040] like Figure 2 As shown in Figure (a), firstly, a high-purity transition metal element is heated and evaporated, so that its atoms or molecules are deposited, adsorbed and fused into the lattice of the epitaxial layer on the substrate surface, forming a few-layer transition metal element layer. Then, a high-purity chalcogen element is heated and evaporated, so that its atoms are inserted between the atoms of the transition metal element layer to form a transition metal chalcogenide compound layer. After post-evaporation treatment, the final few-layer planar structure film is obtained.

[0041] like Figure 2As shown in Figure (b), firstly, a high-purity transition metal element is heated and evaporated, so that its atoms or molecules are deposited, adsorbed and fused into the lattice of the epitaxial layer on the substrate surface, and after a long period of growth, a multi-layer transition metal element layer with a nanorod structure is formed. Subsequently, a high-purity chalcogenide element is heated and evaporated, so that its atoms are inserted between the atoms of the transition metal element layer to form a multi-layer transition metal chalcogenide compound with a nanorod structure. The diffusion speeds of transition metal element and chalcogenide element gas are different. Based on the Kirkendall effect, the post-treatment process allows the chalcogenide element gas to diffuse in the transition metal chalcogenide compound with a nanorod structure to form defects, thereby obtaining a hollow nanotube structure.

[0042] The present invention is described in more detail below using the above-mentioned molecular beam epitaxy equipment and specific process in combination with specific embodiments.

[0043] Embodiment 1:

[0044] See also Figure 1 As shown, a three-inch silicon wafer is used <100> As substrate 4, the stains on the substrate surface were washed away with hydrofluoric acid, acetone and deionized water, and the substrate was vacuum annealed at 100° C. for 12 h.

[0045] The substrate is fixed on the base 3 and placed in the vacuum chamber 1 of the molecular beam epitaxy equipment. High-purity chalcogenide element selenium (Se) is placed in the first beam source furnace 5, and high-purity transition metal element palladium (Pd) is placed in the second beam source furnace 6.

[0046] The molecular beam epitaxy equipment cavity is subjected to multi-stage vacuum treatment using mechanical pumps, molecular pumps, ion pumps, titanium sublimation pumps, etc., so that the vacuum degree of the body reaches 10 -8 pa.

[0047] The substrate temperature was set to 500°C and the substrate rotation speed was set to 0 rad / min.

[0048] The film is deposited using the step evaporation method. First, turn off the first beam source furnace 5 and turn on the second beam source furnace 6. Set the temperature of the second beam source furnace 6 to 1157°C and the deposition rate to The deposition time is 40 minutes, and a palladium (Pd) layer (i.e., a transition metal single substance layer 8) is obtained. Then, the second beam source furnace 6 is closed, and the first beam source furnace 5 is opened. The temperature of the first beam source furnace 5 is set to 125°C, and the deposition rate is The deposition time is 60 minutes. Selenium (Se) atoms are inserted between palladium (Pd) atoms to form transition metal chalcogenide palladium selenide (ie, transition metal chalcogenide layer 9).

[0049] The above film was treated by post-evaporation method. The second beam source furnace 6 was turned off and the first beam source furnace 5 was turned on. The temperature of the first beam source furnace 5 was set to 125°C and the deposition rate was Sedimentation time: 90 min.

[0050] The first beam source furnace 5 and the second beam source furnace 6 are closed to perform thermal annealing on the film. The temperature of the substrate 3 is lowered to 400° C. and kept at that temperature for 60 minutes, then lowered to 300° C. and kept at that temperature for 60 minutes, and then lowered to room temperature.

[0051] Embodiment 2:

[0052] The film microstructure of Example 1 was observed using a scanning electron microscope ( Figure 3 (as shown in Figure a).

[0053] Embodiment 3:

[0054] Compared with Example 1, most of them are the same, except that in this embodiment: a sapphire sheet is used as the substrate.

[0055] Embodiment 4:

[0056] Compared with Example 1, most of the above are the same, except that in this example: during stepwise evaporation, the deposition rate of transition metal element palladium (Pd) is

[0057] Embodiment 5:

[0058] Compared with Example 1, most of the above are the same, except that in this example: during the post-evaporation treatment, the deposition rate of high-purity chalcogen elemental selenium (Se) is The deposition time is 200 min.

[0059] Embodiment 6:

[0060] The microstructure of the film sample in Test Example 5 ( Figure 3 (as shown in Figure b), photoelectron spectrum and surface potential ( Figure 4 ).

[0061] Embodiment 7:

[0062] like Figure 5 As shown, the film described in Example 1 is transferred to a silicon dioxide / silicon substrate 10, a pattern electrode is prepared by electron beam exposure technology, and titanium and gold are deposited as electrodes by electron beam evaporation (i.e., a source electrode 11 and a drain electrode 12 are obtained, respectively), to obtain a back-gate field effect transistor. Based on the excellent electronic and optoelectronic properties of transition metal chalcogenides, this back-gate field effect transistor can be used for ultra-wide spectrum efficient detection of visible light-terahertz.

[0063] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional transition metal chalcogenide compound, characterized in that: The two-dimensional transition metal chalcogenide is used in the field of photoelectric detectors for ultra-wide spectrum and efficient detection of visible light-terahertz; The two-dimensional transition metal chalcogenide is palladium selenide, which is in a multi-layer nanorod structure or a multi-layer nanotube structure; The preparation method of the two-dimensional transition metal chalcogenide compound comprises the following steps: A three-inch silicon wafer was selected as the substrate, and the stains on the substrate surface were washed away with hydrofluoric acid, acetone, and deionized water. The substrate was vacuum annealed at 100°C for 12 hours. The substrate is fixed on the base and placed in a vacuum chamber of a molecular beam epitaxy device, high-purity chalcogenide elemental selenium is placed in a first beam source furnace, and high-purity transition metal elemental palladium is placed in a second beam source furnace; The molecular beam epitaxy equipment cavity is subjected to multi-stage vacuum treatment to achieve a vacuum degree of 10 -8 pa; Set the substrate temperature to 500°C and the substrate rotation speed to 0 rad / min; The film was deposited by step evaporation. First, the first beam source furnace was turned off, and the second beam source furnace was turned on. The temperature of the second beam source furnace was set to 1157°C, and the deposition rate was The deposition time is 40 min to obtain a palladium layer, then the second beam source furnace is closed, the first beam source furnace is opened, and the temperature of the first beam source furnace is set to 125 ° C. The deposition rate is The deposition time is 60 min, and selenium atoms are inserted between palladium atoms to form transition metal chalcogenide palladium selenide; The film formed above was treated by post-evaporation method, the second beam source furnace was turned off, the first beam source furnace was turned on, the temperature of the first beam source furnace was set to 125°C, and the deposition rate was or Sedimentation time: 90min or 200min; The first beam source furnace and the second beam source furnace were turned off, and the above film was subjected to thermal annealing treatment, the substrate temperature was reduced to 400°C, kept at this temperature for 60 minutes, then further reduced to 300°C, kept at this temperature for 60 minutes, and then reduced to room temperature.

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