A purple phosphorus / molybdenum disulfide heterojunction photodetector and its preparation method

Abstract

The present invention discloses a purple phosphorus / molybdenum disulfide heterojunction photodetector and its preparation method. The purple phosphorus / molybdenum disulfide heterojunction photodetector comprises: a substrate; a VP layer formed on the substrate; a MoS2 layer formed on the VP layer; and a metal source electrode and a metal drain electrode formed on the MoS2 layer. The MoS2 layer completely covers the VP layer, and the metal source electrode and the metal drain electrode are arranged in the overlapping portion of the MoS2 and VP layers. The present invention utilizes MoS2 to protect the VP, enabling protection of the VP in air. The resulting photodetector exhibits excellent stability and can withstand long-term exposure to air, overcoming the key application bottleneck of VP instability in air. The present invention utilizes VP and MoS2 to form a heterojunction. Based on the optical gating effect of VP, the VP / MoS2 heterojunction device exhibits extremely high responsivity, detectivity, and external quantum efficiency.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection technology, and in particular to a purple phosphorus / molybdenum disulfide heterojunction photoelectric detector and a preparation method thereof. Background Art

[0002] Photodetectors are electronic devices that convert light signals into electrical signals and are a crucial component of optoelectronic systems. With the advancement of the information age, optoelectronic devices have become widely used in numerous everyday applications, including optoelectronic displays, imaging, environmental monitoring, optical communications, military applications, and security inspections. As a core component of optoelectronic devices, the research and application of photodetectors continues to drive scientific and technological advancements.

[0003] Two-dimensional materials have broad application prospects in the field of next-generation optoelectronic devices due to their unique physical, chemical, and electronic properties. Among them, two-dimensional transition metal dichalcogenides (TMDs, such as MoS2 and WSe2) have thickness-adjustable band gaps, high carrier mobility, strong light-matter interactions, and flexible structures, and can be used to construct high-performance field-effect transistors, photodetectors, memories, solar cells, and spintronic devices. At the same time, two-dimensional materials can be flexibly combined like building blocks. Through design, two-dimensional material heterojunctions can be obtained to compensate for the shortcomings of different two-dimensional materials and thus obtain better optoelectronic properties. Heterojunction structures provide huge opportunities for the preparation of new optoelectronic devices. Therefore, it is very important to explore the heterostructures of high-performance optoelectronic devices based on new two-dimensional materials.

[0004] Purple phosphorus (VP) is an emerging two-dimensional elemental semiconductor with excellent properties, such as rare p-type conductivity and high conductivity up to 7000 cm 2 Purple phosphorus (VP) possesses excellent properties for fabricating high-performance optoelectronic devices, including a high carrier mobility of 1000 nm / (V·s), a monolayer direct band gap of 2.50 eV, exceptional mechanical strength, and unique anisotropy. However, the inherent environmental instability of VP has severely hampered research into its fundamental properties and applications in optoelectronic devices. Therefore, it is imperative to protect the environmental stability of VP and design and fabricate high-performance photodetectors based on it. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a purple phosphorus / molybdenum disulfide heterojunction photodetector and a preparation method to solve the technical problem of the instability of purple phosphorus materials in the air in the existing technology.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solution to achieve the above problems: a purple phosphorus / molybdenum disulfide heterojunction photodetector, the purple phosphorus / molybdenum disulfide heterojunction photodetector comprising:

[0007] substrate; preparing a VP layer on the substrate; preparing a MoS2 layer on the VP layer; preparing a metal source electrode and a metal drain electrode on the MoS2 layer;

[0008] The MoS2 layer completely covers the VP layer, and the metal source electrode and the metal drain electrode are arranged on the overlapping portion of the MoS2 layer and the VP layer.

[0009] The present invention also has the following technical features:

[0010] The substrate is a rigid substrate or a flexible substrate.

[0011] The rigid substrate is a silicon substrate, quartz glass, sapphire or mica with a silicon dioxide insulating layer on the surface;

[0012] The flexible substrate is polyimide, polydimethylsiloxane or polyethylene terephthalate.

[0013] The thickness of the VP layer is 1nm to 150nm.

[0014] The thickness of the MoS2 layer is 1nm to 100nm.

[0015] The metal source electrode or the metal drain electrode is selected from one or a combination of Cr, Ti, Ni, Au, Pd, Pt and Ag.

[0016] The thickness of the metal source electrode or the metal drain electrode is 5nm to 80nm.

[0017] The preparation method of the above-mentioned purple phosphorus / molybdenum disulfide heterojunction photodetector comprises the following steps:

[0018] Step 1: Ultrasonic cleaning of the substrate and drying;

[0019] Step 2: Using a mechanical lift-off transfer method to transfer the underlying two-dimensional semiconductor VP layer to the substrate surface to form a VP layer;

[0020] Step 3: The top two-dimensional semiconductor MoS2 layer is transferred to a polydimethylsiloxane (PDMS) substrate using a mechanical exfoliation transfer method to prepare the MoS2 layer;

[0021] Step 4: Transfer the MoS2 layer prepared in step 3 from the PDMS substrate to the VP layer prepared in step 2 using a micromechanical transfer platform, so that the VP layer is completely covered by the MoS2 layer;

[0022] Step 5: Prepare metal source electrode and metal drain electrode on the substrate, define the electrode shape, and ensure that the metal source electrode and metal drain electrode are arranged in the overlapping part on the MoS2 layer and the VP layer.

[0023] A purple phosphorus / molybdenum disulfide heterojunction photodetector was obtained.

[0024] In step 5, the electrode pattern is defined by using ultraviolet lithography technology, electron beam exposure technology or laser direct writing technology, and the metal source electrode and the metal drain electrode are prepared by combining thermal evaporation, electron beam evaporation or magnetron sputtering and lift-off process.

[0025] The purple phosphorus / molybdenum disulfide heterojunction photodetector is used for photoelectric detection applications.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) The present invention utilizes MoS2 to protect VP, which can achieve protection of VP in air. The prepared photodetector has excellent stability and can be exposed to air for a long time, overcoming the key application bottleneck of VP's instability in air;

[0028] (II) The present invention utilizes VP and MoS2 to construct a heterojunction, with the MoS2 layer serving as a carrier transport channel. The heterojunction region between VP and MoS2 serves as the photosensitive layer of the entire device. Photogenerated carriers generated under illumination are effectively separated at the heterojunction interface. Photogenerated electrons in the VP layer are injected into the MoS2 layer, increasing the current of the photodetector. Photogenerated holes in the MoS2 layer are captured in VP, acting as a localized gate to induce more electrons in the MoS2 and regulate the channel conductance. Based on this light-gating effect, the VP / MoS2 heterojunction device exhibits extremely high responsivity, detectivity, and external quantum efficiency.

[0029] (III) The overall structure of the present invention has the characteristics of simple structure, low cost, high bearing capacity, high reliability and easy maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of the purple phosphorus / molybdenum disulfide heterojunction photodetector.

[0031] Figure 2 This is an optical microscope image of a purple phosphorus / molybdenum disulfide heterojunction photodetector.

[0032] Figure 3 This is the response curve of the purple phosphorus / molybdenum disulfide heterojunction photodetector under different light powers of 532nm light.

[0033] Figure 4 These are the detectivity and external quantum efficiency curves of the purple phosphorus / molybdenum disulfide heterojunction photodetector under different light powers of 532nm light. Figure 5These are the output curves of the VP device before and after being placed in air for three days, and the output curves of the purple phosphorus / molybdenum disulfide heterojunction photodetector before and after being placed in air for one month.

[0034] The meaning of each reference numeral in the accompanying drawings:

[0035] 1-substrate; 2-VP layer; 3-MoS2 layer; 4-metal source electrode 4; 5-metal drain electrode;

[0036] The specific contents of the present invention are further explained in detail below with reference to the embodiments. DETAILED DESCRIPTION

[0037] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0038] The terms "upper", "lower", "front", "back", "top", "bottom", etc. used in the present invention to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operate in a specific direction. "Inside" and "outside" refer to the inside and outside of the contours of the corresponding components, and the above terms should not be understood as limiting the present invention.

[0039] In the present invention, unless otherwise specified, terms such as "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] Unless otherwise specified, all components in the present invention are components known in the prior art.

[0041] Example 1:

[0042] Following the above technical solution, Figure 1-5 As shown, a purple phosphorus / molybdenum disulfide heterojunction photodetector includes, from bottom to top, a substrate 1, a VP layer 2, a MoS2 layer 3, a metal source electrode 4, and a metal drain electrode 5. The MoS2 layer 3 is located above the VP layer 2 and completely covers the VP layer 2. A metal source electrode 4 and a metal drain electrode 5 are arranged above the MoS2 layer 3. The metal source electrode 4 and the metal drain electrode 5 are both placed above the overlapping area of ​​the VP layer 2 and the MoS2 layer 3.

[0043] Here, we construct a VP / MoS2 van der Waals heterostructure by fixing several layers of VP and MoS2 together, aiming to exploit the synergistic effect of the two materials to realize high-performance two-dimensional photodetectors. Furthermore, MoS2 acts as a protective layer for VP, inhibiting its environmental degradation, resulting in high stability of the VP / MoS2 heterostructure device in ambient air.

[0044] As a preferred embodiment of this invention:

[0045] The substrate is a rigid substrate or a flexible substrate.

[0046] The rigid substrate is a silicon substrate, quartz glass, sapphire or mica with a silicon dioxide insulating layer on the surface;

[0047] The flexible substrate is polyimide, polydimethylsiloxane or polyethylene terephthalate.

[0048] The thickness of the VP layer is 1nm to 150nm.

[0049] The thickness of the MoS2 layer is 1nm to 100nm.

[0050] The metal source electrode or the metal drain electrode is selected from one or a combination of Cr, Ti, Ni, Au, Pd, Pt and Ag.

[0051] The thickness of the metal source electrode or the metal drain electrode is 5nm to 80nm.

[0052] As a preferred embodiment of this invention:

[0053] The preparation method of the purple phosphorus / molybdenum disulfide heterojunction photodetector comprises the following steps:

[0054] Step 1: Ultrasonic cleaning of the substrate and drying;

[0055] Step 2: Using a mechanical lift-off transfer method to transfer the underlying two-dimensional semiconductor VP layer to the substrate surface to form a VP layer;

[0056] Step 3: Transfer the top two-dimensional semiconductor MoS2 layer to a polydimethylsiloxane (PDMS) substrate using a mechanical exfoliation transfer method to form a MoS2 layer;

[0057] Step 4: Transfer the MoS2 layer prepared in step 3 from the PDMS substrate to the VP layer prepared in step 2 using a micromechanical transfer platform, so that the VP layer is completely covered by the MoS2 layer;

[0058] Step 5: Prepare metal source electrode and metal drain electrode on the substrate, define the electrode shape, and ensure that the metal source electrode and metal drain electrode are arranged in the overlapping part on the MoS2 layer and the VP layer.

[0059] A purple phosphorus / molybdenum disulfide heterojunction photodetector was obtained.

[0060] In step 5, the electrode pattern is defined by using ultraviolet lithography technology, electron beam exposure technology or laser direct writing technology, and the metal source electrode and the metal drain electrode are prepared by combining thermal evaporation, electron beam evaporation or magnetron sputtering and lift-off process.

[0061] As a preferred embodiment of this invention:

[0062] In this embodiment, the thickness of the VP layer is about 106 nm, and the thickness of the MoS2 layer is about 4 nm.

[0063] In the heterojunction photodetector prepared in this embodiment, the substrate is Si / SiO2; the metal source and drain electrodes are Cr / Au, and the thickness thereof is Cr: 10 nm, and Au: 60 nm.

[0064] The specific steps are as follows:

[0065] 1. VP layer preparation and transfer

[0066] (1) A cut silicon oxide wafer (1 cm × 1 cm) was used as a substrate. The substrate was ultrasonically cleaned in deionized water, acetone, ethanol, and deionized water for 10 min, and then dried with a nitrogen gun for later use.

[0067] (2) The VP layer is obtained by mechanical stripping: Use tweezers to pick up an appropriate amount of VP single crystal and place it on a blue film tape. Use the blank tape area to repeatedly strip the VP material until the VP sample on the tape surface turns light yellow. This is to obtain a thinner VP layer. Then, stick the stripped VP tape on a cleaned and spare silicon wafer, press it gently and let it stand for 5 minutes before peeling off the tape. Then, observe the stripped VP layer under an optical microscope and select a VP layer of appropriate thickness and size for use.

[0068] 2. MoS2 layer preparation and transfer

[0069] The same method as described above was used to prepare MoS2 layers of different thicknesses using the adhesion of the tape, and they were adhered to the PDMS membrane. The adhesion between PDMS and MoS2 was greater than the adhesion between the MoS2 layers, so that the MoS2 layer was peeled off the PDMS membrane.

[0070] 3. Preparation of two-dimensional van der Waals heterojunction VP / MoS2

[0071] (1) The side of the PDMS without MoS2 was glued to the upper surface of a glass slide, and the glass slide with the PDMS side of the MoS2 layer was placed downward on a microscope-assisted micro-area transfer platform;

[0072] (2) Under the microscope, find the previously selected VP layer and MoS2 layer, align the two, slowly turn the knob and constantly adjust their positions in time to keep them close;

[0073] (3) When both the VP layer and the MoS2 layer are clearly visible in the same field of view, heat the substrate to approximately 100°C, bringing the two materials into close contact, and wait for approximately 10 minutes. Raise the glass slide and lift the PDMS membrane to obtain a van der Waals heterojunction of VP / MoS2.

[0074] 4. Preparation of two-dimensional van der Waals heterojunction purple phosphorus / molybdenum disulfide heterojunction photodetector

[0075] (1) The van der Waals heterojunction prepared above was spin-coated with photoresist polymethyl methacrylate (PMMA) using a spin coater and heated at 130°C for 3 minutes; the source and drain electrode patterns were designed using CAD Design 3D Max software; and the electrode patterns were precisely positioned and exposed using an electron beam exposure system, followed by development and fixing;

[0076] (2) Deposit 10nm Cr and 60nm Au by thermal evaporation technology; then clean in acetone to remove the photoresist, and then blow dry with a nitrogen gun to prepare the source and drain electrodes to form a purple phosphorus / molybdenum disulfide heterojunction photodetector, such as Figure 2 shown.

[0077] 5. Photoelectric performance test of two-dimensional van der Waals heterojunction purple phosphorus / molybdenum disulfide heterojunction photodetector

[0078] The sample was irradiated with a laser of 532 nm wavelength, and the photoelectric performance of the prepared VP / MoS2 heterojunction device was tested.

[0079] from Figure 3 and Figure 4 It can be seen that the device shows an ultra-high responsivity (3.82×10 5 A / W), detection rate (9.17×10 13 Jones) and external quantum efficiency (8.91×10 8 %), showing excellent photoelectric detection performance.

[0080] also, Figure 5Stability studies of the VP device and the purple phosphorus / molybdenum disulfide heterojunction photodetector showed that the VP device ceased to conduct after three days in air. In contrast, the purple phosphorus / molybdenum disulfide heterojunction photodetector showed only a slight decrease in conductivity after 30 days of exposure to air, demonstrating its superior air stability. These results demonstrate that the construction of the VP / MoS2 heterojunction not only effectively protects the VP material, but also demonstrates excellent photodetection performance, suggesting promising applications in optoelectronic devices.

[0081] The present invention discloses a purple phosphorus / molybdenum disulfide (VP / MoS2) heterojunction photodetector and its preparation method. The VP / MoS2 heterojunction photodetector comprises, from bottom to top, a substrate, a VP layer, a MoS2 layer, and metal source and drain electrodes. The VP layer is first formed on the substrate, and then the MoS2 layer is transferred to the VP surface. The two semiconductors combine through van der Waals forces to form a van der Waals heterojunction. Metal source and drain electrodes are then formed to form the van der Waals heterojunction photodetector.

[0082] The present invention constructs a van der Waals heterojunction, so that the electrons and holes generated under light conditions are quickly separated at the heterojunction interface, significantly improving the responsiveness, detection rate and external quantum efficiency of the prepared photodetector.

[0083] What has been described above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be conceived by any technician familiar with the field within the technical scope disclosed by the present invention without creative work are all covered by the scope of protection of the present invention.

Claims

1. A purple phosphorus / molybdenum disulfide heterojunction photodetector, characterized in that: The purple phosphorus / molybdenum disulfide heterojunction photodetector comprises: Si / SiO2 substrate; Preparing a VP layer on the substrate; Preparing a MoS2 layer on the VP layer; Preparing a metal source electrode and a metal drain electrode on the MoS2 layer; The MoS2 layer completely covers the VP layer; The metal source electrode and the metal drain electrode are placed on the overlapping portion of the MoS2 layer and the VP layer; The thickness of the VP layer is 1 nm to 150 nm; The thickness of the MoS2 layer is 1 nm to 100 nm; The thickness of the metal source electrode or the metal drain electrode is 5 nm to 80 nm.

2. The purple phosphorus / molybdenum disulfide heterojunction photodetector according to claim 1, wherein: The metal source electrode or the metal drain electrode is selected from one or a combination of Cr, Ti, Ni, Au, Pd, Pt and Ag.

3. The method for preparing the purple phosphorus / molybdenum disulfide heterojunction photodetector according to claim 1 or 2, characterized in that: The steps include: Step 1: Ultrasonic cleaning of the Si / SiO2 substrate and drying; Step 2: Transfer the two-dimensional semiconductor VP layer to the surface of the Si / SiO2 substrate using a mechanical lift-off transfer method to form a VP layer; Step 3: Transfer the two-dimensional semiconductor MoS2 layer to the polydimethylsiloxane substrate using a mechanical exfoliation transfer method to form a MoS2 layer; Step 4: Transfer the MoS2 layer prepared in step 3 from the PDMS substrate to the VP layer prepared in step 2 using a micromechanical transfer platform, so that the VP layer is completely covered by the MoS2 layer; Step 5: Prepare a metal source electrode and a metal drain electrode on the substrate, define the electrode shape, and ensure that the metal source electrode and the metal drain electrode are arranged in the overlapping part of the MoS2 layer and the VP layer to obtain a purple phosphorus / molybdenum disulfide heterojunction photodetector.

4. The method for preparing the purple phosphorus / molybdenum disulfide heterojunction photodetector according to claim 3, It is characterized by: In step 5, the electrode pattern is defined by using ultraviolet lithography technology, electron beam exposure technology or laser direct writing technology, and the metal source electrode and the metal drain electrode are prepared by combining thermal evaporation, electron beam evaporation or magnetron sputtering and lift-off process.

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