Molybdenum ditelluride / nickel ditelluride heterojunction-based photoelectric detector and preparation method and application thereof

Abstract

The invention belongs to the technical field of photoelectric detection, and discloses a molybdenum ditelluride / nickel ditelluride heterojunction-based photoelectric detector and a preparation method and application thereof, and the molybdenum ditelluride / nickel ditelluride heterojunction-based photoelectric detector is prepared by stripping single crystal molybdenum ditelluride onto an oxide layer silicon substrate through a mechanical stripping method to obtain a molybdenum ditelluride nanosheet; a nickel ditelluride nanosheet is obtained through a chemical vapor deposition method; the molybdenum ditelluride nanosheet is transferred to the nickel ditelluride nanosheet through a PVA dry transfer method to form an overlapped part, and a molybdenum ditelluride / nickel ditelluride heterojunction is formed; and preparing electrodes at two ends of the molybdenum ditelluride / nickel ditelluride heterojunction through electron beam evaporation or thermal evaporation. The photoelectric detector utilizes a built-in electric field generated by a two-dimensional material heterojunction interface to effectively improve the photoelectric conversion efficiency and response speed of a visible light wave band.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detection, and more particularly relates to a photoelectric detector based on a molybdenum ditelluride / nickel ditelluride heterojunction and a preparation method and application thereof. BACKGROUND

[0002] As a kind of core device for converting optical signals into detectable electrical signals, photoelectric detectors have wide application prospects in the fields of biological imaging, medical detection, environmental detection, military reconnaissance, etc. In order to meet the rapid development of modern information technology, new photoelectric detectors are required to have wider detection ranges, faster acquisition speeds and lower preparation costs. Therefore, research on new photoelectric detectors is urgently needed.

[0003] As a new photoelectric material in the transition metal chalcogenide (TMD S ) family, molybdenum ditelluride has a narrow band gap of 1.0-1.3 eV, and can achieve high absorption and high response in the visible and infrared light ranges, so it has attracted extensive research attention. However, its long response time and poor stability limit its development. Nickel ditelluride, also a TMD S system, has type II Dirac semimetal characteristics, and its Dirac point is very close to the Fermi level, so its carrier mobility and recovery speed are significantly better than those of traditional TMD S , which provides a new way to compensate for the shortcomings of molybdenum ditelluride. SUMMARY

[0004] In order to solve the above problems and shortcomings of the prior art, the application aims to provide a photoelectric detector based on a molybdenum ditelluride / nickel ditelluride heterojunction. The photoelectric detector forms a heterojunction with molybdenum ditelluride and nickel ditelluride to improve the photoelectric detection performance in the visible light range, including the on-off ratio, response speed, etc., and also improves the stability of the device.

[0005] Another object of the application is to provide a preparation method of the photoelectric detector based on the molybdenum ditelluride / nickel ditelluride heterojunction. The method uses chemical vapor deposition and mechanical exfoliation to prepare molybdenum ditelluride / nickel ditelluride as a heterojunction photoelectric detector, which greatly improves the photoelectric performance of the device in the visible light range, and has a simple process and stable performance.

[0006] Still another object of the application is to provide an application of the photoelectric detector based on the molybdenum ditelluride / nickel ditelluride heterojunction.

[0007] The objects of the application are achieved by the following technical solutions: A photoelectric detector based on a molybdenum ditelluride / nickel ditelluride heterojunction comprises a silicon dioxide / silicon substrate, a molybdenum ditelluride / nickel ditelluride heterojunction, and metal electrodes; the molybdenum ditelluride / nickel ditelluride heterojunction is an overlapping portion of molybdenum ditelluride nanosheets and nickel ditelluride nanosheets, and metal electrodes are arranged at both ends of the molybdenum ditelluride nanosheets and the nickel ditelluride nanosheets outside the heterojunction region.

[0008] Preferably, the thickness of the molybdenum ditelluride nanosheets is 35-45 nm, the thickness of the nickel ditelluride nanosheets is 40-55 nm, the metal electrodes are titanium and gold, and the thicknesses are 10-15 nm and 60-65 nm, respectively.

[0009] The preparation method of the photoelectric detector based on the molybdenum ditelluride / nickel ditelluride heterojunction comprises the following specific steps: S1. Single-crystal molybdenum ditelluride is exfoliated onto a silicon dioxide / silicon substrate by a mechanical exfoliation method to obtain molybdenum ditelluride nanosheets; S2. Nickel ditelluride nanosheets are prepared on the silicon dioxide / silicon substrate by a chemical vapor deposition method using Te powder and NiCl2·6H2O as raw materials at a chemical vapor deposition reaction temperature of 550-700 ℃; S3. The molybdenum ditelluride nanosheets are transferred onto the nickel ditelluride nanosheets by a PVA dry transfer method to form an overlapping portion, thereby preparing a molybdenum ditelluride / nickel ditelluride heterojunction; S4. Electrodes are arranged at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction by electron beam evaporation or thermal evaporation, thereby preparing a photoelectric detector based on the molybdenum ditelluride / nickel ditelluride heterojunction.

[0010] Further, the specific steps of step S2 are as follows: S21. The silicon dioxide / silicon substrate layer is sequentially placed in an acetone solution, anhydrous ethanol, and deionized water for ultrasonic cleaning to remove surface contaminants, and is then blown dry with high-purity nitrogen after cleaning; S22. The Te powder is placed in a quartz boat, the NiCl2·6H2O is placed in another quartz boat, and the silicon dioxide / silicon substrate layer is placed with the front face downward above the NiCl2·6H2O; the quartz boat containing the Te powder is placed in the high-temperature constant-temperature zone upstream of the quartz tube cavity, and the quartz boat containing the NiCl2·6H2O and the silicon dioxide / silicon substrate layer is placed in the constant-temperature zone downstream of the quartz tube cavity; S23. Inert gas is introduced at a flow rate of 200 sccm for 3-5 minutes to purge the air from the quartz tube. After the gas is introduced, the upstream high-temperature zone is heated to 550-700 ℃ at a rate of 13-15 ℃ / min. During the heating process, the flow rate of the inert gas is controlled at 50-70 sccm. After the target temperature is reached, the temperature is held at 20-30 sccm. After holding for 5-20 minutes, the flow rate of the inert gas is adjusted to 50-70 sccm. When the temperature inside the furnace cools down to below 100 ℃, the gas flow is turned off. The nanosheets are then removed at room temperature to obtain nickel ditelluride nanosheets.

[0011] Preferably, the inert gas in step S23 is a mixture of hydrogen and nitrogen, wherein the volume ratio of hydrogen to nitrogen is (1~5):(95~99).

[0012] Furthermore, the specific steps of step S3 are as follows: S31. PVA is titrated on PDMS and dried at 55~60 ℃ for 10~12 min to form a PVA film; S32. Place PDMS loaded with PVA film on a quartz plate, align it with a silicon dioxide / silicon substrate layer with molybdenum ditelluride through a two-dimensional material transfer stage, and heat treat it at 92~95℃ for 4~6 min to make molybdenum ditelluride nanosheets adhere to PVA / PDMS. S33. PVA / PDMS with attached molybdenum ditelluride nanosheets is aligned with a silicon dioxide / silicon substrate with nickel ditelluride through a two-dimensional material transfer stage, so that the molybdenum ditelluride nanosheets and nickel ditelluride nanosheets partially overlap. The substrate is then placed on a heating stage and baked at 98~101℃ for 4~6 min. After that, it is placed in deionized water at 55~60℃ until the PVA is completely dissolved to obtain a molybdenum ditelluride / nickel ditelluride heterojunction.

[0013] Furthermore, the specific method for step S4 is as follows: S41. Apply positive photoresist to a silicon dioxide / silicon substrate containing a molybdenum ditelluride / nickel ditelluride heterojunction and spin coat it at 3000~4000 rpm / min for 1~2 min in a spin coater, then bake it at 100~106℃ for 4~6 min; align it using a photolithography machine, expose it with ultraviolet light using a mask, develop it with a developer and dry it to photolithographically create an electrode pattern; S42. Using electron beam or thermal evaporation, deposit Ti with a thickness of 10-15 nm and Au with a thickness of 60-65 nm on its surface; place it in acetone solution to remove excess gold and photoresist, remove residual acetone with deionized water, blow dry, and then heat treat at 150-155℃ for 30-40 min in a nitrogen atmosphere to obtain electrodes at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction.

[0014] The application of the photodetector based on molybdenum ditelluride / nickel ditelluride heterojunction in the field of photoelectric detection technology.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses molybdenum ditelluride / nickel ditelluride as a heterojunction. Through the built-in electric field generated at the molybdenum ditelluride / nickel ditelluride interface, photogenerated electron-hole pairs can be effectively separated under visible light, which is beneficial for improving the performance under weak light (light power density as low as 0.81 mW / cm²). 2 It can detect under the influence of the atmosphere and has a considerable self-driving effect.

[0016] 2. The photodetector of the present invention comprises a silicon dioxide / silicon substrate, a molybdenum ditelluride / nickel ditelluride heterojunction, and a metal electrode. Nickel ditelluride nanosheets are prepared by chemical vapor deposition and used in a photodetector with molybdenum ditelluride / nickel ditelluride as a heterojunction, which greatly improves the photoelectric performance of the device under visible light. The process is simple, the performance is stable, and it has application potential. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a tube furnace used in the preparation process of nickel ditelluride nanosheets using chemical vapor deposition in this invention. Figure 2 This is a schematic diagram of the photodetector based on the molybdenum ditelluride / nickel ditelluride heterojunction (MoTe2 / NiTe2) of the present invention; Figure 3 These are optical microscope images of the molybdenum ditelluride nanosheets and the photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction prepared by mechanical exfoliation in Example 1. Figure 4 This is a current-voltage curve of the molybdenum ditelluride / nickel ditelluride photodetector of Example 1 at different optical power densities at 405 nm. Figure 5 This is a time-resolved optical diagram of the molybdenum ditelluride / nickel ditelluride photodetector of Example 1 and a conventional molybdenum ditelluride photodetector under the same optical power density under 405 nm light illumination. Figure 6 These are optical microscope images of the molybdenum ditelluride nanosheets and the photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction prepared by mechanical exfoliation in Example 2. Figure 7 This is a current-voltage curve of the molybdenum ditelluride / nickel ditelluride photodetector in Example 2 at different optical power densities at 405 nm. Figure 8This is a time-resolved optical diagram of the molybdenum ditelluride / nickel ditelluride photodetector of Example 2 and a conventional molybdenum ditelluride photodetector under the same optical power density under 405 nm light illumination. Figure 9 This is a current-voltage curve of the molybdenum ditelluride / nickel ditelluride photodetector in Example 3 at different optical power densities at 405 nm. Figure 10 This is a time-resolved optical diagram of the molybdenum ditelluride / nickel ditelluride photodetector of Example 3 and the molybdenum ditelluride / nickel ditelluride photodetector of Example 2 at the same optical power density at 405 nm. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0019] Figure 1 This is a schematic diagram of a tube furnace used in the preparation process of nickel ditelluride nanosheets using chemical vapor deposition (CVD) according to the present invention. Figure 1 As shown, the vapor deposition apparatus for preparing nickel ditelluride nanosheets includes a quartz tube 1. The interior of the quartz tube 1 is divided into an upstream isothermal zone 2 and a downstream isothermal zone 3. A quartz boat 4 loaded with tellurium powder (Te) is placed in the upstream isothermal zone 2 of the tube furnace. A quartz boat 5 loaded with NiCl2·6H2O and a silicon dioxide / silicon substrate 6, placed face down on top of the quartz boat, are placed in the downstream isothermal zone 3 of the tube furnace. The apparatus also includes heating devices for heating the high-temperature isothermal zones (upstream and downstream isothermal zones). Both ends of the quartz tube 1 have vents; the vent at the left end (upstream of the carrier gas) is the inlet, and the vent at the right end is the outlet.

[0020] Example 1 A photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction, such as Figure 2 As shown, a molybdenum ditelluride / nickel ditelluride heterojunction is formed by the overlapping portion of a silicon dioxide / silicon substrate 1, nickel disulfide nanosheets 2, and molybdenum ditelluride nanosheets 3. Metal electrodes 4 are symmetrically disposed at both ends of the nickel ditelluride nanosheets 2 and molybdenum ditelluride nanosheets 3 outside the heterojunction region, and the metal electrodes 4 do not simultaneously contact the nickel disulfide nanosheets 2 and the molybdenum ditelluride nanosheets. The thickness of the nickel ditelluride nanosheets 2 is 50±3 nm, the thickness of the molybdenum ditelluride nanosheets 3 is 42±2 nm, and the metal electrodes 4 are titanium and gold electrodes, with the titanium having a thickness of 10 nm and the gold having a thickness of 60 nm.

[0021] 1. Place a 20 mm × 20 mm silicon dioxide / silicon substrate in acetone solution and ultrasonically clean it for 15 min to remove organic matter adhering to its surface. After cleaning, ultrasonically clean it with anhydrous ethanol for 15 min to remove the residual acetone solution on the silicon dioxide / silicon substrate. Finally, ultrasonically clean it with deionized water for 15 min to remove the residual ethanol and particles on the substrate surface. After cleaning, blow it dry with high-purity nitrogen gas.

[0022] 2. Place 120 mg of tellurium (Te) powder (99.99% purity) and 30 mg of nickel chloride hexahydrate (NiCl2·6H2O) into different quartz boats. Place the quartz boat containing Te powder in the high-temperature isothermal zone upstream of the quartz tube chamber, and place the quartz boat containing NiCl2·6H2O and silicon dioxide / silicon substrate in the isothermal zone downstream of the quartz tube chamber. A mixture of hydrogen and nitrogen gas with a volume ratio of 1%:99% was introduced into a quartz tube. The gas was first introduced at a flow rate of 200 sccm for 5 minutes to purge the air from the quartz tube. After the air was completely expelled, the upstream high-temperature zone was heated to 550 ℃ at a rate of 13 ℃ / min, with the flow rate of the mixed gas controlled at 60 sccm during the heating process. Once the target temperature was reached, the temperature was maintained at 30 sccm for 5 minutes. After this period, the flow rate was adjusted to 60 sccm. The gas flow was then stopped when the furnace temperature cooled below 100 ℃, and the nanosheets were removed at room temperature, yielding nickel ditelluride nanosheets with a thickness of 50±3 nm.

[0023] 3. Single-crystal molybdenum ditelluride was exfoliated onto a silicon dioxide / silicon substrate by mechanical exfoliation to obtain molybdenum ditelluride nanosheets with a thickness of 42±2 nm.

[0024] 4. Molybdenum ditelluride nanosheets are transferred onto a silicon dioxide / silicon substrate carrying nickel ditelluride nanosheets to form a molybdenum ditelluride / nickel ditelluride heterojunction. Specifically, a polyvinyl alcohol (PVA) solution was titrated onto a polydimethylsiloxane (PDMS) film, dried at 56 °C for 10 min to form a film, and then the PDMS with the PVA film was placed on a quartz glass slide. The slide was then aligned with a silicon dioxide / silicon substrate containing molybdenum ditelluride (MoDDI) using a two-dimensional material transfer stage. The slide was then heat-treated at 93 °C for 4 min to allow MoDDI nanosheets to adhere to the PVA. The PVA / PDMS with the MoDDI nanosheets was then aligned with a silicon dioxide / silicon substrate containing nickel ditelluride (NiDDI) using the two-dimensional material transfer stage, ensuring partial overlap between the NiDDI and MoDDI nanosheets. The slide was then placed on a heating stage and baked at 101 °C for 4 min, followed by immersion in deionized water at 56 °C for 2 min to completely dissolve the PVA, thus obtaining a MoDDI / NiDDI heterojunction.

[0025] 5. Positive photoresist was applied to a silicon dioxide / silicon substrate of a molybdenum ditelluride / nickel ditelluride heterojunction and spin-coated at 3000 rpm / min for 2 min. The substrate was then baked at 100 °C for 5 min. Following this, alignment was achieved using a photolithography machine, followed by UV exposure with a mask, development, and drying to create the electrode pattern. Then, 10 nm of Ti and 60 nm of Au were deposited on the surface using electron beam or thermal evaporation. Finally, the sample was placed in acetone to remove excess gold and photoresist, and residual acetone was removed with deionized water. After drying, the sample was heat-treated at 155 °C for 35 min under a nitrogen atmosphere. Electrodes were then placed at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction to fabricate a photodetector. Figure 3 As shown.

[0026] The photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction prepared in Example 1 was tested, and the results are as follows: Figure 4 and Figure 5 As shown. Figure 4 This shows the current-voltage curves of the photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction in Example 1 at different optical power densities at 405 nm. From... Figure 4 It is known that the rectification ratio of the molybdenum ditelluride / nickel ditelluride heterojunction is 100, which is caused by the Schottky contact between the molybdenum ditelluride nanosheets and the nickel ditelluride nanosheets. The heterojunction achieves an on / off ratio of 120, indicating that the Schottky barrier and built-in electric field formed at the interface of the molybdenum ditelluride and nickel ditelluride nanosheets significantly improve the separation efficiency of photogenerated electron-hole pairs and support the self-driven working mode. Figure 5 The optical power density of the molybdenum ditelluride / nickel ditelluride photodetector in Example 1, compared to that of a conventional molybdenum ditelluride photodetector, is 207.22 mW / cm² under 405 nm light illumination. 2 Time-resolved light map. From Figure 5 It can be seen that after transferring nickel ditelluride nanosheets to form a molybdenum ditelluride / nickel ditelluride heterojunction, the photocurrent increased by 2.5 times compared with the traditional molybdenum ditelluride photodetector, indicating that the photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction has better photoelectric detection performance.

[0027] Example 2 1. Place a 20 mm × 20 mm silicon dioxide / silicon substrate in acetone solution and ultrasonically clean it for 15 min to remove organic matter adhering to its surface. After cleaning, ultrasonically clean it with anhydrous ethanol for 15 min to remove the residual acetone solution on the silicon dioxide / silicon substrate layer. Finally, ultrasonically clean it with deionized water for 15 min to remove the residual ethanol and particles on the substrate surface. After cleaning, blow it dry with high-purity nitrogen gas.

[0028] 2. Place 120 mg of tellurium (Te) powder (99.99% purity) and 30 mg of nickel chloride hexahydrate (NiCl2·6H2O) separately in different quartz boats. Place the quartz boat containing Te powder in the high-temperature isothermal zone upstream of the quartz tube chamber, and place the boat containing NiCl2... 2· A quartz boat containing 6H2O and a silicon dioxide / silicon substrate was placed in a constant-temperature zone downstream of the quartz tube chamber. A mixture of hydrogen and nitrogen gas, with a volume ratio of 5%:95%, was introduced into the quartz tube at a flow rate of 200 sccm for 5 minutes to purge the air from the quartz tube. After the air was completely expelled, the upstream high-temperature zone was heated to 650 ℃ at a heating rate of 15 ℃ / min, with the flow rate of the mixed gas controlled at 60 sccm during the heating process. After reaching the target temperature, the temperature was held at 30 sccm for 20 minutes, and then the flow rate of the mixed gas was adjusted to 60 sccm. The gas flow was then shut off when the furnace temperature cooled to below 100 ℃, and the nanosheets were removed at room temperature, yielding nickel ditelluride nanosheets with a thickness of 43±3 nm.

[0029] 3. Single-crystal molybdenum ditelluride was exfoliated onto a silicon dioxide / silicon substrate by mechanical exfoliation to obtain few-layer molybdenum ditelluride nanosheets with a thickness of 37±2 nm.

[0030] 4. Molybdenum ditelluride nanosheets are transferred onto a silicon dioxide / silicon substrate carrying nickel ditelluride nanosheets to form a molybdenum ditelluride / nickel ditelluride heterojunction. Specifically, a polyvinyl alcohol (PVA) solution was titrated onto a polydimethylsiloxane (PDMS) film, dried at 57 °C for 11 min to form a film, and then the PDMS with the PVA film was placed on a quartz glass slide. It was then aligned with a silicon dioxide / silicon substrate with molybdenum ditelluride through a two-dimensional material transfer stage and heat-treated at 94 °C for 5 min to allow molybdenum ditelluride nanosheets to adhere to the PVA. The PVA / PDMS with the attached molybdenum ditelluride nanosheets was then aligned with a silicon dioxide / silicon substrate with nickel ditelluride through a two-dimensional material transfer stage, so that the nickel ditelluride nanosheets and molybdenum ditelluride nanosheets partially overlapped. It was then placed on a heating stage and baked at 101 °C for 5 min, and then immersed in deionized water at 57 °C for 2 min to allow the PVA to completely dissolve, thus obtaining a molybdenum ditelluride / nickel ditelluride heterojunction.

[0031] 5. Positive photoresist was applied to a silicon dioxide / silicon substrate of a molybdenum ditelluride / nickel ditelluride heterojunction and spin-coated at 3000 rpm / min for 2 min. The substrate was then baked at 102 °C for 5 min. Following this, alignment was achieved using a photolithography machine, followed by UV exposure with a mask, development, and drying to create the electrode pattern. Then, 12 nm of Ti and 62 nm of Au were deposited on the surface using electron beam or thermal evaporation. Finally, the sample was placed in acetone to remove excess gold and photoresist, and residual acetone was removed with deionized water. After drying, the sample was heat-treated at 155 °C for 38 min under a nitrogen atmosphere. Electrodes were then placed at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction to fabricate a photodetector. Figure 6 As shown.

[0032] The photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction prepared in Example 2 was tested, and the results are as follows: Figure 7 and Figure 8 As shown. Figure 7 This shows the current-voltage curves of the photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction in Example 2 at different optical power densities at 405 nm. From... Figure 7 It can be seen that the rectification ratio of the molybdenum ditelluride / nickel ditelluride heterojunction is 10. 3 This is caused by the Schottky contact between molybdenum ditelluride nanosheets and nickel ditelluride nanosheets. The heterojunction achieves an on / off ratio of 544, indicating that the Schottky barrier and built-in electric field formed at the interface of molybdenum ditelluride nanosheets and nickel ditelluride nanosheets significantly improve the separation efficiency of photogenerated electron-hole pairs and support the self-driven working mode. Figure 8 The optical power density of the molybdenum ditelluride / nickel ditelluride photodetector in Example 2 and the conventional molybdenum ditelluride photodetector under 405 nm light illumination is 101.23 mW / cm². 2 Time-resolved light map. From Figure 8 It can be seen that after transferring nickel ditelluride to form a heterojunction, the photocurrent of the photodetector is increased by 4 times compared with the traditional molybdenum ditelluride photodetector, which proves that the photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction has better photoelectric detection performance.

[0033] Example 3 The difference from Example 2 is that the photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction was stored for more than 6 months. The photodetector of the molybdenum ditelluride / nickel ditelluride heterojunction prepared in Example 2 was stored in a dehumidifier for 6 months and then tested. The results are as follows... Figure 9 and Figure 10 As shown. Figure 9 This is the current-voltage curve of the photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction in Example 3 at different optical power densities at 405 nm. From...Figure 9 It can be seen that the rectification ratio of the molybdenum ditelluride / nickel ditelluride heterojunction after 6 months of storage is still 10. 3 This is caused by the Schottky contact between molybdenum ditelluride and nickel ditelluride. This heterojunction achieves an on / off ratio of 410, which indicates that the Schottky barrier and built-in electric field formed at the interface of molybdenum ditelluride and nickel ditelluride significantly improve the separation efficiency of photogenerated electron-hole pairs and support the self-driven working mode. Figure 10 The optical power density of the molybdenum ditelluride / nickel ditelluride photodetector in Example 3 and the molybdenum ditelluride photodetector in Example 2 under 405 nm light illumination is 184.84 mW / cm². 2 Time-resolved light map. From Figure 10 It can be seen that after 6 months of storage, the optical circuit of the molybdenum ditelluride / nickel ditelluride heterojunction photodetector still maintains excellent performance compared with the molybdenum ditelluride photodetector before 6 months, which proves that the molybdenum ditelluride / nickel ditelluride heterojunction photodetector has stable photoresponse characteristics and good practical potential.

[0034] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction, characterized in that, The photodetector includes a silicon dioxide / silicon substrate, a heterojunction of nickel telluride nanosheets / molybdenum telluride nanosheets, and a metal electrode; the heterojunction of nickel telluride nanosheets / molybdenum telluride nanosheets is the overlapping portion of nickel telluride nanosheets and molybdenum telluride nanosheets, and metal electrodes are respectively disposed at both ends of the nickel telluride nanosheets and molybdenum telluride nanosheets outside the heterojunction region.

2. The photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 1, characterized in that, The thickness of the molybdenum ditelluride nanosheets is 35-45 nm, the thickness of the nickel ditelluride nanosheets is 40-55 nm, and the metal electrodes are titanium and gold, with thicknesses of 10-15 nm and 60-65 nm, respectively.

3. The method for fabricating a photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 1 or 2, characterized in that, The specific steps include the following: S1. Single-crystal molybdenum ditelluride was exfoliated onto a silicon oxide substrate by mechanical exfoliation to obtain molybdenum ditelluride nanosheets; S2. Nickel ditelluride nanosheets were prepared on a silicon oxide / silicon substrate by chemical vapor deposition (CVD) using Te powder and NiCl2·6H2O as raw materials at 550~700 °C. S3. Molybdenum ditelluride nanosheets were transferred onto nickel ditelluride nanosheets to form overlapping portions, thereby obtaining a molybdenum ditelluride / nickel ditelluride heterojunction. S4. A photodetector for a molybdenum ditelluride / nickel ditelluride heterojunction is fabricated by depositing metal electrodes at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction through electron beam evaporation or thermal evaporation.

4. The method for fabricating a photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 3, characterized in that, The specific steps of step S2 are as follows: S21. The silicon dioxide / silicon substrate layer is sequentially placed in acetone solution, anhydrous ethanol and deionized water for ultrasonic cleaning to remove surface contaminants. After cleaning, it is dried with high-purity nitrogen. S22. Place the Te powder on a quartz boat, place the NiCl2·6H2O on another quartz boat, and place the silicon dioxide / silicon substrate layer face down on top of the NiCl2·6H2O; place the quartz boat containing the Te powder in the high-temperature isothermal zone upstream of the quartz tube chamber, and place the quartz boat containing the NiCl2·6H2O and the silicon dioxide / silicon substrate layer in the isothermal zone downstream of the quartz tube chamber; S23. Inert gas is introduced at a flow rate of 200 sccm for 3-5 minutes to purge the air from the quartz tube. After the gas is introduced, the upstream high-temperature zone is heated to 550-700 ℃ at a rate of 13-15 ℃ / min. During the heating process, the flow rate of the inert gas is controlled at 50-70 sccm. After the target temperature is reached, the temperature is held at 20-30 sccm. After holding for 5-20 minutes, the flow rate of the inert gas is adjusted to 50-70 sccm. When the temperature inside the furnace cools down to below 100 ℃, the gas flow is turned off. The nanosheets are then removed at room temperature to obtain nickel ditelluride nanosheets.

5. The method for fabricating a photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 4, characterized in that, The inert gas in step S23 is a mixture of hydrogen and nitrogen, with a volume ratio of (1~5):(95~99).

6. The method for fabricating a photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 3, characterized in that, The specific steps of step S3 are as follows: S31. PVA is titrated on PDMS and dried at 55~60 ℃ for 10~12 min to form a PVA film; S32. Place PDMS loaded with PVA film on a quartz plate, align it with a silicon dioxide / silicon substrate layer with molybdenum ditelluride through a two-dimensional material transfer stage, and heat treat it at 92~95℃ for 4~6 min to make molybdenum ditelluride nanosheets adhere to PVA / PDMS. S33. PVA / PDMS with attached molybdenum ditelluride nanosheets is aligned with a silicon dioxide / silicon substrate with nickel ditelluride through a two-dimensional material transfer stage, so that the molybdenum ditelluride nanosheets and nickel ditelluride nanosheets partially overlap. The substrate is then placed on a heating stage and baked at 98~101℃ for 4~6 min. After that, it is placed in deionized water at 55~60℃ until the PVA is completely dissolved to obtain a molybdenum ditelluride / nickel ditelluride heterojunction.

7. The method for fabricating a photodetector based on a molybdenum ditelluride / nickel ditelluride heterojunction according to claim 3, characterized in that, The specific method for step S4: S41. Apply positive photoresist to a silicon dioxide / silicon substrate containing a molybdenum ditelluride / nickel ditelluride heterojunction and spin coat it at 3000-4000 rpm / min for 1-2 min in a spin coater, then bake it at 100-106 ℃ for 4-6 min; align it using a photolithography machine, expose it with ultraviolet light using a mask, develop it with a developer and dry it to photolithographically create an electrode pattern; S42. Using electron beam or thermal evaporation, deposit Ti with a thickness of 10-15 nm and Au with a thickness of 60-65 nm on its surface; place it in acetone solution to remove excess gold and photoresist, remove residual acetone with deionized water, blow dry, and then heat treat at 150-155℃ for 30-40 min under nitrogen to obtain electrodes at both ends of the molybdenum ditelluride / nickel ditelluride heterojunction.

8. The application of the photodetector based on molybdenum ditelluride / nickel ditelluride heterojunction as described in claim 1 or 2 in the field of photodetector technology.

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