Heterojunction vertical device based on graphene / tungsten disulfide / tantalum nickel selenide crystal, preparation method and application

Abstract

The present invention relates to a graphene / tungsten disulfide / tantalum nickel selenide crystal-based heterojunction vertical device, preparation method, and application, belonging to the field of light detection. The heterojunction vertical device comprises, from bottom to top, a Si / SiO2 substrate, graphene, WS2, and Ta2NiSe5, with two electrodes on the graphene and Ta2NiSe5, respectively. The preparation method comprises: mechanically exfoliating the graphene, WS2, and Ta2NiSe5; sequentially transferring the three materials onto Si / SiO2 using a PVA dry transfer method; photolithography to define the electrode positions; and thermally evaporating the electrodes. The prepared thin-film device exhibits excellent self-driven light detection performance and has advantages such as stable performance. As a photodetector, it can detect light from visible light to the mid-infrared band. The thick Ta2NiSe5 structure enhances the detector's absorption of mid-infrared light, giving the detector the advantages of high sensitivity, simple device structure, and strong practicality.

Description

Technical Field

[0001] The present invention relates to the field of light detection technology, in particular to an infrared detector and a preparation method thereof. Background Art

[0002] Photodetectors detect light radiation by converting light signals into electrical signals and converting light energy into electrical quantities, depending on how the device responds to radiation. They have a wide range of applications in the military and the national economy. In the visible and near-infrared bands, they are primarily used for radiation measurement and detection, industrial automation, and photometry. In the infrared band, they are primarily used for infrared thermal imaging and infrared remote sensing.

[0003] Most two-dimensional transition metal chalcogenides, such as MoS2, RsSe2, and WS2, possess properties such as tunable band gaps, strong light-matter interactions, enhanced light absorption, excellent mechanical flexibility, and adjustable carrier density and polarity. Ta2NiSe5, a novel material within the vast family of two-dimensional transition metal chalcogenides, possesses high electron mobility and a relatively small monolayer band gap of 0.36 eV, making it ideal for use in broad-spectrum photodetectors from the visible to mid-infrared. Photodetectors with a broadband spectral response play an important role in optical communications, medical imaging, environmental monitoring, analytical applications, gas sensing, and security monitoring. [The following appears to be unrelated and should likely be omitted.] The photoconductivity effect of Ta2NiSe5 photodetectors was also investigated. Experiments have also shown that it exhibits significant anisotropy. These results suggest potential applications in new electronics and optoelectronics.

[0004] The van der Waals heterojunction formed by vertically stacking two-dimensional materials and the corresponding optoelectronic devices have also received a lot of attention and research. However, the heterojunctions constructed by two materials that have been developed in large quantities are limited by the length of the conductive channel and the long transfer path of photogenerated carriers, and the response of the photodetectors prepared is relatively low. For example, the Chinese invention patent application with publication number CN113066888A discloses a self-driven photodetector based on an In2S3 nanosheet array / Si pyramid array heterojunction and the Chinese invention patent application with publication number CN112885922A discloses a photodetector based on a PtSe2 and silicon nanopillar array and its preparation method to achieve detection functions from visible light to near-infrared bands and show good self-driven light detection performance, with advantages such as stable performance. Among them, two layers of materials are commonly used to build a homojunction, which will have certain defects in performance. Summary of the Invention

[0005] This application conducts in-depth research on the Ta2NiSe5 material. Due to its inherently small band gap, the top light-absorbing layer responds to the far-infrared band. In view of this, the first purpose of the present invention is to provide a graphene / WS2 / Ta2NiSe5-based heterojunction vertical device, the second purpose is to provide a method for preparing the above-mentioned heterojunction vertical device, and the third purpose is to provide the application of the above-mentioned heterojunction vertical device in photoelectric detection equipment. The photodetector prepared using the heterojunction vertical device has high light absorption rate, responsivity and photoelectric conversion efficiency.

[0006] The specific scheme adopted in the present invention is:

[0007] A graphene / WS2 / Ta2NiSe5-based heterojunction vertical device comprises, from bottom to top, a Si / SiO2 substrate, a graphene film layer, a WS2 film layer in direct contact with the graphene film layer, and a Ta2NiSe5 film layer in direct contact with the WS2 film layer, with two electrodes on the graphene film layer and the Ta2NiSe5 film layer, respectively; wherein, the electrode on the graphene film layer is connected to the source electrode, and the electrode on the Ta2NiSe5 film layer is connected to the drain electrode.

[0008] As a further optimization of the above solution, the thickness of the graphene thin film layer is 50 to 100 nm, the thickness of the WS2 thin film layer is 20 to 40 nm, and the thickness of the Ta2NiSe5 thin film layer is 100 to 200 nm.

[0009] The method for preparing the above-mentioned heterojunction vertical device comprises the following steps:

[0010] Step 1: Graphene, WS2 and Ta2NiSe5 are adhered to Si / SiO2 substrate using mechanical exfoliation method;

[0011] Step 2: Graphene, WS2 and Ta2NiSe5 are transferred sequentially onto a Si / SiO2 substrate using a PVA dry method to obtain a vertical heterojunction structure of graphene-WS2-Ta2NiSe5 with vertical arrangement;

[0012] Step 3: Forming electrode patterns through photolithography and development;

[0013] Step 4: evaporating metal on the electrode pattern mask in step 3 to form a source electrode and a drain electrode, with a channel region between the source electrode and the drain electrode;

[0014] Step 5: High temperature annealing to obtain a heterojunction vertical device.

[0015] In step 4, the metals used for the source electrode and the drain electrode are selected from one or two of Au, Cu, Ni, Ti, Cr and Ag, more preferably Au, Ni / Au or Ti / Au.

[0016] In step five, the annealing temperature is preferably 100°C to 300°C, more preferably 200°C to 300°C.

[0017] In step five, the annealing is preferably performed in a nitrogen (N2) or argon (Ar) atmosphere.

[0018] Application of the above-mentioned heterojunction vertical device in photoelectric detection equipment.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] (1) The heterojunction vertical device described in the present invention comprises a graphene layer (bottom layer), a WS2 layer (middle layer), and a Ta2NiSe5 layer (top layer) arranged sequentially from bottom to top on a conductive substrate. The bottom graphene layer is not in direct contact with the top Ta2NiSe5 layer. The top Ta2NiSe5 layer is used to absorb photogenerated carriers, while the bottom graphene layer can rapidly extract photogenerated carriers due to its ultrahigh carrier mobility.

[0021] (2) The bottom material graphene is not in direct contact with the top material Ta2NiSe5, while the middle layer material WS2 is in direct contact with the top and bottom materials at the overlapping position, forming a vertical conductive channel, which greatly shortens the movement distance of the photogenerated carriers.

[0022] (3) The top layer material Ta2NiSe5 is combined with the middle layer WS2 through van der Waals force to form a heterojunction; WS2 is an n-type semiconductor. After contacting with Ta2NiSe5, due to the concentration difference between electrons and holes, the carriers diffuse and move, forming a space charge depletion region at the interface, and a built-in electric field appears; graphene and WS2 are combined through van der Waals force to form an ohmic contact; the diffusion movement direction of the carriers is opposite to the drift movement direction generated by the built-in electric field, and eventually the concentrations of the two carriers will reach a thermal equilibrium; the diffusion movement direction of the carriers is opposite to the drift movement direction generated by the built-in electric field, and eventually the concentrations of the two carriers will reach a thermal equilibrium; the photogenerated carriers will be separated by the built-in electric field and conducted to the external circuit by the graphene upper electrode and the metal electrode on the Ta2NiSe5 to generate electrical signals.

[0023] (4) The photodetector adopts a vertical incidence method, that is, the incident direction of the incident light is from the top layer of Ta2NiSe5 through the middle layer of WS2 to the bottom layer of graphene, presenting a vertical structural heterojunction as a whole.

[0024] (5) The present invention improves the response and absorption of the photodetector to the far-infrared band by optimizing the light-absorbing layer of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the cross-sectional structure of a graphene / WS2 / Ta2NiSe5 vertical device provided in Example 1 of the present invention;

[0026] Figure 2 This is a physical picture of the graphene / WS2 / Ta2NiSe5 vertical device and metal electrodes provided in Example 1 of the present invention;

[0027] Figure 3 405 nm laser irradiation is the IV characteristic curve of the graphene / WS2 / Ta2NiSe5 vertical device provided in Example 1 of the present invention;

[0028] Figure 4 1 is the IT characteristic curve of the graphene / WS2 / Ta2NiSe5 vertical device provided in Example 1 of the present invention under laser irradiation of different wavelengths;

[0029] Figure 5 spectral response diagram of the graphene / WS2 / Ta2NiSe5 vertical device provided in Example 1 of the present invention;

[0030] Figure 6 This is the Raman graph of WS2 and Ta2NiSe5 provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention improves the performance of photodetectors through methods such as PVA dry transfer, photolithographic gold plating, and nitrogen annealing. Specifically, a three-layer heterojunction is first constructed on a Si / SiO2 substrate using PVA dry transfer. Then, titanium-gold electrodes are prepared using photolithographic gold plating and nitrogen annealing, resulting in a self-driven vertical photodetector device with excellent performance.

[0032] Preparation method of vertical device based on graphene / WS2 / Ta2NiSe5:

[0033] 1) Select graphene, WS2, and Ta2NiSe5 single crystal materials, and mechanically exfoliate graphene, WS2, and Ta2NiSe5 on a conductive substrate;

[0034] 2) Graphene, WS2, and Ta2NiSe5 are transferred sequentially onto a conductive substrate through PVA dry transfer to build a double-layer homojunction; wherein, the first two-dimensional material layer (graphene), the second two-dimensional material layer (WS2), and the third two-dimensional material layer (Ta2NiSe5) are formed on the conductive substrate from bottom to top.

[0035] 3) forming an electrode pattern on the substrate by photolithography and development;

[0036] 4) evaporating metal on the electrode pattern mask, then removing the photoresist on the substrate, forming a source electrode and a drain electrode at both ends thereof, with a channel region between the source electrode and the drain electrode;

[0037] 5) Setting the first two-dimensional material (graphene) to the source electrode and the third two-dimensional material (Ta2NiSe5) to the drain electrode, and then performing annealing to form ohmic contacts between the first two-dimensional material layer, the third two-dimensional material layer, the source electrode, and the drain electrode to obtain an overall vertical device.

[0038] Preferably, the conductive substrate is selected from a silicon substrate.

[0039] Preferably, the first two-dimensional material layer is selected from graphene, and the material of the second two-dimensional material layer is selected from MoS2, WS2, MoSe2, WSe2, and MoTe2.

[0040] Preferably, the metals used for the source electrode and the drain electrode are selected from one or two of Au, Cu, Ni, Ti, Cr and Ag.

[0041] In order to illustrate the present invention more intuitively and in detail, the following specific embodiments are provided below in conjunction with the accompanying drawings, but the implementation methods and protection scope of the present invention are not limited thereto.

[0042] Example 1

[0043] The preparation method of a vertical device based on two-dimensional materials graphene / WS2 / Ta2NiSe5 specifically includes the following steps:

[0044] (1) A graphene thin film layer 6, a WS2 thin film layer 2, and a Ta2NiSe5 thin film layer 3 are prepared on a Si / SiO2 substrate 1 using a mechanical exfoliation method. The graphene and WS2 are directly exfoliated onto the Si / SiO2 substrate using tape, while the Ta2NiSe5 is transferred onto the Si / SiO2 substrate using polydimethylsiloxane (PDMS). In this step, the thicknesses of the graphene, WS2, and Ta2NiSe5 obtained on the Si / SiO2 surface using the mechanical exfoliation method are 50-100 nm, 20-40 nm, and 100-200 nm, respectively.

[0045] (2) Graphene, WS2, and Ta2NiSe5 were sequentially transferred onto a Si / SiO2 substrate using PVA dry transfer, wherein the bottom layer was graphene, the middle layer was WS2, and the top layer was Ta2NiSe5. In this step, the dry transfer method produced a vertically arranged graphene-WS2-Ta2NiSe5 heterojunction structure. PVA was prepared by stirring 4 g of PVA particles with 21 ml of deionized water to form a viscous liquid.

[0046] (3) Electrodes are photoetched on the bottom material and the top material by spin coating photoresist and photolithography using a photolithography machine. Metal is evaporated on the electrode pattern mask, and then the photoresist on the insulating dielectric layer is removed to form a source electrode 5 and a drain electrode 4 at both ends thereof.

[0047] (4) Metal is deposited on the electrodes by thermal evaporation. The metal used is preferably one or two selected from Au, Cu, Ni, Ti, Cr, and Ag, and more preferably Au, Ni / Au, or Ti / Au. In the present invention, the source and drain electrodes and the channel region are fabricated using photolithography and metal evaporation techniques. In this embodiment, the source and drain electrodes are both Ti / Au electrodes. The Ti layer is in contact with the insulating dielectric layer and may have a thickness of 1 nm to 50 nm, such as 30 nm. The Au layer may have a thickness of 10 nm to 100 nm, such as 70 nm.

[0048] (5) Metal is evaporated on the electrode pattern mask, and then the photoresist on the insulating dielectric layer is removed to form a source electrode 5 and a drain electrode 4 at both ends thereof, with a channel region between the source electrode and the drain electrode.

[0049] (6) Remove excess titanium with acetone solution.

[0050] (7) Annealing with nitrogen, wherein the high temperature annealing temperature is preferably 100°C to 300°C, more preferably 200°C to 300°C; the annealing is preferably carried out in a gas atmosphere of nitrogen (N2) or argon (Ar), and the device is processed so that the obtained device forms an ohmic contact with the source and drain electrodes, and a homojunction is formed between the materials.

[0051] The cross-sectional structure of the prepared heterojunction vertical device is shown in Figure 2. Figure 1 shown.

[0052] A bias of 0.5V is applied to the positive electrode of the vertical device, and the vertical device emits an ultra-wide spectrum covering white light to the mid-infrared region. The performance of the device is tested, and the test results are as follows: the optical photo and spectrum of the device are as follows Figure 2 、 5 As shown, the spectrum ranges from 400-2300nm, completely covering the visible light region, with a peak wavelength around 650nm.

[0053] The positive and negative electrodes of the vertical device were connected to a current detector with a bias voltage of 0.5V. Under illumination conditions within the 400-2300nm range, the device functioned as a photodetector. Performance testing revealed that the device exhibited a wide spectral response. During the test, a semiconductor laser light source was used to illuminate the sample and the photocurrent was measured, revealing that photocurrent was present under illumination from ultraviolet to infrared light.

[0054] The positive and negative electrodes of the vertical device were connected to a current detector, with a bias voltage of 0V. Under illumination conditions within the 400-2300nm range, the vertical device could be used as a photodetector. Its performance was tested, and the IV curve results showed that applying light at 0V resulted in an increase in current.

[0055] The vertical device of the present invention can simultaneously realize self-driving characteristics and light detection characteristics, and the device has good performance and a wide light emission range, which can cover the ultraviolet to mid-infrared band.

[0056] It should be noted that the above-described embodiments are to be understood as illustrative and not limiting of the scope of protection of the present invention, which is subject to the claims. It will be apparent to those skilled in the art that non-essential improvements and adjustments to the present invention, without departing from the spirit and scope of the present invention, still fall within the scope of protection of the present invention.

Claims

1. A graphene / WS2 / Ta2NiSe5 heterojunction vertical device, characterized by: The heterojunction vertical device comprises, from bottom to top, a Si / SiO2 substrate, a graphene film layer, a WS2 film layer in direct contact with the graphene film layer, and a Ta2NiSe5 film layer in direct contact with the WS2 film layer, with two electrodes respectively on the graphene film layer and the Ta2NiSe5 film layer; wherein the electrode on the graphene film layer is connected to the source electrode, and the electrode on the Ta2NiSe5 film layer is connected to the drain electrode; The heterojunction vertical device is prepared by the following steps: Step 1: Graphene, WS2 and Ta2NiSe5 are adhered to Si / SiO2 substrate using mechanical exfoliation method; Step 2: Graphene, WS2 and Ta2NiSe5 are transferred sequentially onto a Si / SiO2 substrate using a PVA dry method to obtain a vertical heterojunction structure of graphene-WS2-Ta2NiSe5 with vertical arrangement; Step 3: Forming electrode patterns through photolithography and development; Step 4: evaporating metal on the electrode pattern mask in step 3 to form a source electrode and a drain electrode, with a channel region between the source electrode and the drain electrode; Step 5: High temperature annealing to obtain a heterojunction vertical device.

2. The graphene / WS2 / Ta2NiSe5-based heterojunction vertical device according to claim 1, characterized in that: The thickness of the graphene film layer is 50-100 nm, the thickness of the WS2 film layer is 20-40 nm, and the thickness of the Ta2NiSe5 film layer is 100-200 nm.

3. The graphene / WS2 / Ta2NiSe5-based heterojunction vertical device according to claim 1, characterized in that: In step 4, the metals used for the source electrode and the drain electrode are selected from one or two of Au, Cu, Ni, Ti, Cr and Ag.

4. The graphene / WS2 / Ta2NiSe5-based heterojunction vertical device according to claim 3, characterized in that: The metal used for the source electrode and the drain electrode is Au, Ni / Au or Ti / Au.

5. The graphene / WS2 / Ta2NiSe5-based heterojunction vertical device according to claim 1, characterized in that: In step five, the annealing temperature is 100°C to 300°C.

6. The graphene / WS2 / Ta2NiSe5-based heterojunction vertical device according to claim 1, characterized in that: In step five, the annealing is performed in a nitrogen or argon atmosphere.

7. Use of the heterojunction vertical device according to any one of claims 1 to 6 in a photoelectric detection device.

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