Methods for modifying MoTe2 semimetal and photodetectors based on modified MoTe2 semimetal

Abstract

The application belongs to the technical field of photoelectric detection, and discloses a semi-metal MoTe2 modification method and a photoelectric detector based on semi-metal MoTe2. The semi-metal MoTe2 crystal is laid on a 3M adhesive tape and pressed. The 3M adhesive tape is repeatedly torn and pasted 4-6 times. The film is pasted on a glass slide. The 3M adhesive tape is aligned with the film and pasted. The 3M adhesive tape is quickly torn off. The film is pasted on a silicon wafer and heated. The film is slowly lifted. MoTe2 nanometer thin crystals on the substrate are irradiated by 266nm Q-switched laser to obtain modified semi-metal MoTe2. A nickel / gold electrode is prepared on a silicon dioxide substrate to obtain a substrate I. The modified MoTe2 nanometer thin crystals are combined with the substrate I to obtain a photoelectric detector. The preparation process is simple, the photoelectric performance is significantly improved, and the prepared photoelectric detector can realize high responsivity and sensitivity in a wide spectral range.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, and relates to a method for modifying the semi-metal MoTe2 and a photoelectric detector based on the modified semi-metal MoTe2. Background Technology

[0002] A photodetector is a device that converts optical signals into electrical signals. It mainly consists of an optical probe, a preamplifier, a signal processor, and an output interface. The optical probe is responsible for converting light radiation into electrical signals, the preamplifier amplifies the electrical signals, and the signal processor digitizes the processed signals and transmits them to the output interface. Photodetectors are widely used in optical communication, optoelectronics, biomedicine, environmental monitoring, and many other fields. Traditional photodetectors are limited in practical applications due to their high cost, complex manufacturing process, inflexibility, and limited application scenarios. However, with the continuous development of electronic, information, and optical technologies, photodetector technology is also constantly evolving. Taking the communication field as an example, fiber optic communication has become the mainstream of modern communication, and photodetectors, as core optoelectronic components, play a crucial role in fiber optic communication. They primarily utilize the high speed and high precision of photodetectors to convert optical signals transmitted through optical fibers into usable electrical signals. Commonly used photodetectors in fiber optic communication include PIN photodiodes, APD photodiodes, and MSA photodiodes. Among them, PIN photodiodes, due to their simple structure and low cost, can be used for short- and medium-distance communication.

[0003] Photodetectors have wide applications in environmental sensing, artificial intelligence robotics, optical data transmission, medical and military fields. However, fabricating high-performance photodetectors requires characteristics such as fast response time, good photoresponsivity, high sensitivity, and high efficiency. Furthermore, to enable the mobility of photogenerated carriers in the photodetector, a bias voltage is often required. However, this method increases the size of the optoelectronic device, thus limiting its application in various complex environments. To address this, current research mainly focuses on developing novel materials to improve these characteristics. For example, two-dimensional materials offer promise for miniaturized, integrated single-cell direct detectors due to their high carrier mobility, fast electron-hole pair separation rate, and strong interaction with photons over a broad spectral range.

[0004] Taking silicon-based semiconductors as an example, traditional silicon-based photodetectors are relatively mature. Their high sensitivity allows the photoelectric effect based on silicon materials to generate large current changes even under very low light intensity. Simultaneously, silicon-based photodetectors have high response speeds, making them suitable for high-speed communication and computing applications. However, due to wavelength and material limitations, they are mainly applicable to the visible and near-infrared ranges, exhibiting poor absorption at certain specific wavelengths, thus limiting their applications. While traditional materials such as HgCdTe, InGaAs, and InSb can cover the infrared spectral range, these types of detectors only achieve high sensitivity under low-temperature conditions. In contrast, using two-dimensional materials simplifies the device manufacturing process, and the response speed and responsivity of photodetectors can be improved through the design and control of two-dimensional material structures. For example, invention patent CN110010785A discloses a near-infrared photodetector based on the two-dimensional material WSe2. Specifically, this invention constructs a heterojunction by stacking two-dimensional WSe2 with graphene and ReS2, utilizing the anisotropy of ReS2 to achieve polarization-sensitive detection. The bottom layer of P-type WSe2 and the top layer of N-type ReS2 form a built-in electric field, which allows photogenerated carriers to separate rapidly upon illumination. This invention is low-cost and simple to manufacture. Based on the high absorption coefficient and high carrier mobility of WSe2 for near-infrared light, it can achieve high-sensitivity photodetection. However, the detector of this invention has a weak response in other wavelength bands, making it difficult to achieve broadband detection, which limits its application in the field of multi-band optical detection.

[0005] Although this two-dimensional transition metal sulfide can achieve broadband detection when constructed into heterojunctions with other materials, it suffers from poor interfacial stability and difficulties in bandgap matching, which limits the development of broadband detectors. Material modification is a potentially effective solution to reduce these drawbacks. Ultraviolet Q-switched lasers, with their high photon energy, readily induce oxidation doping effects on material surfaces, making them an important means of altering material properties. For example, invention patent CN106733474B discloses a method for ultraviolet laser-assisted synthesis of metal oxide / graphene composite materials. Specifically, the metal oxide in the composite material prepared by this invention can be selected from ZnO, TiO2, CuO, etc. Irradiation of the mixed solution with an ultraviolet laser causes the metal salt to react with graphene oxide, generating metal oxide nanoparticles to obtain the composite material. This invention is inexpensive, simple to manufacture, and easy to mass-produce. By adjusting the parameters of the ultraviolet laser, such as wavelength, power, and irradiation time, the size, shape, and distribution of particles can be precisely controlled. However, this invention can only change the microscopic morphology, and there are currently no reports on the effect of ultraviolet nanosecond lasers on the photoelectric properties of materials.

[0006] Based on the above analysis, the existing technologies have the following problems and shortcomings: photodetectors utilizing optical, thermal, and electrical effects are limited by the external environment and their own band gap, making it impossible to achieve broadband detection. Furthermore, there is a lack of suitable solutions to improve the interface stability and bandgap matching of broadband detectors. Although ultraviolet lasers have been proposed to modify materials, current material modification efforts are limited to altering material morphology and have not yet been applied to the modification of photoelectric properties in two-dimensional transition metal materials, which restricts the development of broadband detectors. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] The purpose of this invention is to provide a method for modifying the semi-metal MoTe2 and a photodetector based on the modified semi-metal MoTe2, thereby improving the accuracy of material processing, broadening the application range of the semi-metal MoTe2, and providing new opportunities for the research and commercial production of high-performance optoelectronic devices.

[0009] (II) Technical Solution

[0010] To solve the above technical problems, such as Figure 1 As shown, the present invention provides a method for modifying the half-metal MoTe2, comprising the following steps:

[0011] S1: Lay the half-metallic MoTe2 crystal flat on 3M tape and press it down;

[0012] S2: Repeatedly tear and stick the 3M tape 4-6 times, and observe it under a microscope to confirm whether it meets the thickness and area requirements, and obtain thin-layer MoTe2 crystal I;

[0013] S3: Adhere the 8mm×8mm PDMS film to the glass slide;

[0014] S4: Align the 3M tape in S2 with the PDMS film in S3 and stick it on. Take a picture under a microscope to record the relative position of the nanosheet with the surrounding environment and hold it with an eraser.

[0015] S5: Quickly peel off the 3M tape to obtain MoTe2 nanocrystals I on the PDMS film, and fix the PDMS film with MoTe2 crystals on the robotic arm above the substrate stage;

[0016] S6: Fine-tune the z-axis to slowly lower the robotic arm until the PDMS film in S5 is firmly attached to the silicon wafer containing 400nm thick SiO2, and heat the metal clamp of the robotic arm.

[0017] S7: Stop heating, slowly lift the robotic arm, remove the substrate, and obtain MoTe2 nanocrystals I on the Si / SiO2 substrate to complete the transfer;

[0018] S8: Modified half-metal MoTe2 can be obtained by irradiating the MoTe2 nanocrystal I on the substrate in S7 with a 266nm Q-switched laser.

[0019] Furthermore, the MoTe2 crystals in S1 are synthesized by chemical vapor deposition (CVD), the 3M tape is 3M8153LE transfer film, and the pressing time is 20 seconds.

[0020] Furthermore, the thickness of the MoTe2 crystal I in S2 is 50-70 nm; the PDMS film in S3 is Gel-pak PF-3-x4.

[0021] Furthermore, the time spent holding the rubber clamp in S4 is 20 hours.

[0022] Furthermore, the thickness of the MoTe2 nanocrystals I obtained on the PDMS film in S5 is 50-70 nm.

[0023] Furthermore, the heating temperature in S6 is 70 degrees Celsius, and the heating time is 20 minutes.

[0024] Furthermore, such as Figure 2 As shown, the specific implementation method of S8 is as follows:

[0025] S81: A high-precision three-dimensional adjustment frame is used to adjust the position of the crystal in S7 to ensure that the crystal is within the coverage area of ​​the light spot;

[0026] S82: Set the output power of the 266nm Q-switched laser to 8mW, and adjust the spot size to a power density of 3W cm⁻¹ using the lens group. -2 ;

[0027] S83: Set the output time of the 266nm Q-switched laser to 25s.

[0028] Another objective of this invention is to provide a photodetector based on modified half-metal MoTe2, comprising a modified MoTe2 nanocrystal I, a source metal electrode II, a drain metal electrode III, a SiO2 insulating layer IV, and a Si substrate V, connected sequentially from top to bottom.

[0029] Furthermore, such as Figure 3 As shown, the fabrication method of the photodetector based on the modified half-metal MoTe2 includes the following steps:

[0030] Step 21: Nickel / gold source metal electrode II and nickel / gold drain metal electrode III are fabricated on Si substrate V and silicon dioxide substrate IV using photolithography and thermal evaporation techniques to obtain substrate I;

[0031] Step 22: Combine the modified MoTe2 nanocrystal I in S8 with the substrate I in step 1 to obtain the photodetector.

[0032] Furthermore, the thicknesses of the nickel electrode and the gold electrode in step 21 are 10 nm and 50 nm, respectively.

[0033] Furthermore, such as Figure 4 As shown, the specific implementation method of step 22 is as follows:

[0034] Step 221: Repeat the operations of S1-S5 to obtain MoTe2 nanocrystals I on the PDMS film;

[0035] Step 222: Place substrate I from step 1 on the vacuum adsorption stage and turn on the vacuum adsorption function to fix substrate I.

[0036] Step 223: Using a metallographic microscope, align the PDMS film from step 21 with the positions of source metal electrode II and drain metal electrode III from step 22, and slowly attach the film to the source metal electrode II and drain metal electrode III. Set the heating temperature to 70 degrees and the heating time to 20 minutes.

[0037] Step 224: Turn off the heating switch, slowly lift the PDMS film, and fix the MoTe2 nanocrystal I above the source metal electrode II and drain metal electrode III in step 22;

[0038] Step 225: Irradiate the MoTe2 nanocrystal I on the substrate in step 24 with a 266nm Q-switched laser to obtain the modified photodetector.

[0039] (III) Beneficial Effects

[0040] The above-described technical solution provides a method for modifying the MoTe2 semimetal and a photodetector based on the modified MoTe2 semimetal, which have the following advantages:

[0041] First, the modification method is simple, inexpensive, and can achieve local modification; the photodetector fabrication process is simple, the photocurrent is significantly improved, and high responsivity and sensitivity can be achieved over a wide spectral range.

[0042] Secondly, the modification method can generate high-energy pulses in a short time with good beam quality, focusing to a smaller spot size, thus improving energy density and processing accuracy. The photodetector has a wide spectral response and high detectivity, enabling rapid photoelectric conversion and signal transmission. By changing the phase structure of MoTe2, forming heterojunctions with other materials, or applying an external electric field, its electrical and photoelectric properties can be effectively controlled.

[0043] Third, the modification method reduces costs, the preparation process is relatively simple, and it is compatible with existing semiconductor manufacturing processes. It is expected to reduce the manufacturing cost of optoelectronic devices, improve production efficiency, and promote the large-scale application and market penetration of optoelectronic devices.

[0044] Fourth, modification of the half-metal MoTe2 leads to the following significant technological advancements:

[0045] 1. Nanoscale fabrication: Using mechanical exfoliation and micromechanical transfer techniques, MoTe2 crystals can be precisely fabricated and transferred to obtain uniform nanosheet materials. Such size control provides a foundation for realizing higher-performance nanoelectronic devices.

[0046] 2. Improvement of physical properties: Laser irradiation modification technology can effectively control the electronic structure of MoTe2, achieve precise modification of specific parts, and change the microstructure, thereby improving its photoelectric conversion efficiency and obtaining some special properties, which is of great significance for the development of new electronic and energy devices.

[0047] 3. Interface and compatibility: MoTe2 nanocrystals prepared on silicon-based Si / SiO2 substrates are compatible with existing semiconductor manufacturing processes, enabling better integration into silicon-based integrated circuits, realizing the integration of optoelectronic devices and traditional electronic devices, and promoting the diversification of chip functions.

[0048] 4. Controllability and repeatability: By using modification processes such as Q-switched laser irradiation, the depth and range of the treatment can be precisely controlled, ensuring that the modified half-metal MoTe2 crystal has a high degree of controllability and repeatability in terms of physical and chemical properties.

[0049] 5. Environmental impact: This method is relatively environmentally friendly. Compared with traditional chemical methods, it reduces the use of harmful chemicals and greatly reduces the harm to the environment.

[0050] 6. Potential for mass production: Due to the relatively simple preparation process and the potential for further development for mass production as production scales up and costs decrease, these technologies have the potential to drive the development of related industries.

[0051] 7. This not only improves the performance of the semi-metallic MoTe2, but also expands its application in fields such as optical communication, imaging technology, environmental monitoring, and biomedicine. Attached Figure Description

[0052] Figure 1 This is a flowchart of the half-metal MoTe2 modification method provided in the embodiments of the present invention;

[0053] Figure 2This is a flowchart of the method for irradiating MoTe2 nanocrystals on a substrate with a 266nm Q-switched laser, provided in an embodiment of the present invention.

[0054] Figure 3 This is a flowchart of the fabrication method of a photodetector based on modified half-metal MoTe2 provided in an embodiment of the present invention;

[0055] Figure 4 This is a flowchart of a method for combining modified MoTe2 nanocrystals I and substrate I according to an embodiment of the present invention;

[0056] Figure 5 This is a schematic diagram of the modified half-metal MoTe2 photodetector structure provided in an embodiment of the present invention;

[0057] Figure 6 This is a schematic diagram of the atomic structure of the half-metal MoTe2 provided in an embodiment of the present invention;

[0058] Figure 7 This is a diagram showing the electrical performance of the modified half-metal MoTe2 photodetector provided in an embodiment of the present invention.

[0059] Figure 8 This is the ultraviolet light response diagram of the modified half-metal MoTe2 photodetector provided in the embodiments of the present invention;

[0060] Figure 9 This is the visible light response diagram of the modified half-metal MoTe2 photodetector provided in the embodiments of the present invention;

[0061] Figure 10 This is the visible light response diagram of the unmodified half-metal MoTe2 photodetector provided in this embodiment of the invention;

[0062] Figure 11 This is the infrared light response diagram of the unmodified half-metal MoTe2 photodetector provided in the embodiment of the present invention. Detailed Implementation

[0063] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0064] Example 1: Modification method of half-metal MoTe2

[0065] 1. Material preparation: First, obtain high-quality half-metal MoTe2 crystal samples.

[0066] 2. Mechanical peeling method: Place the half-metallic MoTe2 crystal on 3M tape, press gently to ensure good contact between the crystal and the tape, and then perform 4-6 repeated rapid peeling and pasting operations. Observe under a microscope to prepare a uniformly thick MoTe2 nanofilm crystal.

[0067] 3. Transfer Process: Prepare an 8mm × 8mm PDMS film and attach it to a clean, undamaged glass slide. Then, align and attach 3M tape containing a thin layer of MoTe2 nanoparticles to the PDMS film, and quickly peel off the tape to transfer the MoTe2 nanocrystals onto the PDMS film. Finally, fix the PDMS film to the robotic arm above the slide stage.

[0068] 4. Heating and Transfer: Fine-tune the Z-axis to slowly lower the robotic arm until the PDMS film is transferred onto a pre-prepared silicon wafer containing a 400nm thick SiO2 layer, and then heated at 70°C to enhance the adhesion of the crystal.

[0069] 5. Laser irradiation modification: MoTe2 nanocrystals on a Si / SiO2 substrate were irradiated using a 266nm Q-switched laser. The laser power and irradiation time were optimized to achieve effective modification of the MoTe2 nanocrystals.

[0070] Example 2: Modification method of half-metal MoTe2

[0071] 1. Material preparation: MoTe2 nanocrystals were grown on a specific substrate by chemical vapor deposition (CVD).

[0072] 2. Transfer to the target substrate: Using micromechanical transfer technology, the CVD-grown MoTe2 nanocrystals are transferred from the growth substrate to a silicon wafer containing 400 nm thick SiO2. During the transfer process, precise position control is crucial to ensure the flatness and integrity of the nanocrystals.

[0073] 3. Modification process: The transferred MoTe2 nanocrystals are placed on a temperature-controlled platform, and a thin metal film is deposited on their surface using electron beam evaporation technology to improve their electrical properties.

[0074] 4. Post-processing: After coating, the silicon wafer is placed in a vacuum annealing furnace for annealing to remove surface impurities and further improve the conductivity and structural stability of MoTe2.

[0075] The two examples above demonstrate different techniques for the preparation, transfer, and modification of nanocrystals, involving fundamental materials science and surface engineering techniques such as mechanical exfoliation, laser irradiation, micromechanical transfer, electron beam evaporation, and vacuum annealing. The specific implementation of these techniques will depend on precise experimental operations and strict condition control, with the ultimate goal of improving and optimizing the properties of the half-metal MoTe2 material.

[0076] Example 3: Fabrication of a photodetector based on modified MoTe2

[0077] Required materials and equipment:

[0078] half-metal MoTe2 crystal

[0079] 3M 8153LE transfer film

[0080] PDMS thin film and glass slide

[0081] Silicon wafer containing 400nm thick SiO2

[0082] Photolithography and thermal evaporation equipment

[0083] Metallurgical microscope

[0084] 266nm Q-switched laser

[0085] step:

[0086] 1. MoTe2 nanocrystals were obtained on PDMS film using mechanical exfoliation (as described in steps S1-S5 above).

[0087] 2. Use photolithography on a Si substrate to fabricate source and drain metal electrodes of appropriate shape and size.

[0088] 3. A 10nm thick nickel layer and a 50nm thick gold layer are deposited on the electrode using thermal evaporation technology.

[0089] 4. The obtained MoTe2 nanocrystals are aligned and bonded to the prefabricated source and drain electrodes using micromechanical transfer technology, and then subjected to heat treatment to improve contact quality.

[0090] 5. MoTe2 nanocrystals were irradiated with a 266nm Q-switched laser to modify the half-metal MoTe2.

[0091] 6. Finally, the photodetector is fabricated through the above steps.

[0092] Example 4: Fabrication of a photodetector (variant) based on modified MoTe2

[0093] Required materials and equipment:

[0094] Same as Example 1

[0095] step:

[0096] 1. By employing laser micro-exfoliation technology instead of mechanical exfoliation, more precise and uniform MoTe2 nanocrystals can be obtained.

[0097] 2. Electron beam evaporation is used instead of thermal evaporation to form metal electrodes, improving the fineness and adsorption of the electrode metal layer.

[0098] 3. During the PDMS transfer process, a local heating method is applied to more precisely control the impact of heat treatment on material properties.

[0099] 4. Micro-patterns are fabricated on MoTe2 nanocrystals using photolithography to obtain more complex photoelectric response characteristics in subsequent photoelectric tests.

[0100] 5. For the laser modification process, the effects of different parameters on the modification effect were studied by changing the wavelength and power of laser irradiation.

[0101] 6. Conduct detailed performance tests on the completed photodetector.

[0102] The two embodiments provided in this invention illustrate the specific steps from preparing modified MoTe2 nanocrystals to completing the fabrication of a photodetector. In actual operation, appropriate adjustments need to be made based on laboratory conditions and equipment. Furthermore, experimental safety procedures should be followed, and a thorough performance evaluation should be conducted to ensure that the newly prepared detector meets the expected application requirements.

[0103] The embodiments of the present invention have achieved some positive results in the research and development and use process, and have indeed great advantages compared with the prior art. The following content will describe them in conjunction with the data, charts and other information of the experimental process.

[0104] Existing semi-metallic photodetectors, such as the invention patent with publication number CN109870234B, disclose a photodetector based on the semi-metallic molybdenum distellide, with an operating wavelength range of 532nm-10.6μm and a photocurrent in the nanoampere range. However, the semi-metallic MoTe2 photodetector irradiated with ultraviolet laser proposed in this invention patent has a wider operating wavelength, higher photocurrent, and higher response capability. The significant improvement in performance stems from ultraviolet laser irradiation of the semi-metallic MoTe2, which modifies the MoTe2 semi-metallic material and simultaneously improves photocurrent and quantum efficiency.

[0105] like Figure 5 As shown, based on the above embodiments, a method for fabricating a photodetector based on modified half-metal MoTe2 is described in detail, specifically including the following steps:

[0106] S1: The half-metallic MoTe2 crystal synthesized by chemical vapor transport method is spread on a 3M8153LE transfer film and pressed for 20 seconds. If the pressing time is less than 20 seconds, it is not easy to obtain a large-sized thin layer of MoTe2 crystal. If the pressing time is greater than 30 seconds, it is not easy to obtain a thin layer of MoTe2 crystal, which affects the modification effect and the subsequent performance of the photodetector.

[0107] S2: Repeatedly tear and stick 3M tape 4-6 times to obtain a thin layer of MoTe2 crystals;

[0108] S3: Adhere the PF-3-x4PDMS film from the 8mm×8mm Gel-pak onto the glass slide;

[0109] S4: Align the S23M tape with the S3 PDMS film and stick it on. Clamp it with a rubber for 20 hours. It is not easy to obtain large-size thin-layer MoTe2 crystals if the clamping time is less than 12 hours. The clamping time is more than 24 hours and has almost no effect on the thickness of the peeled crystal.

[0110] S5: Quickly peel off the 3M tape to obtain MoTe2 nanocrystals on the PDMS film, wherein the thickness of the MoTe2 crystals is 57nm;

[0111] S6: The PDMS film described in S5 is attached to a silicon wafer containing 400nm thick SiO2 and heated. The heating temperature is set to 70 degrees and the heating time is 20 minutes.

[0112] S7: Slowly lift the PDMS film to obtain MoTe2 nanocrystals on the Si / SiO2 substrate;

[0113] S8: Use a high-precision three-dimensional adjustment frame to adjust the crystal position described in S7, ensuring the crystal is within the beam spot coverage area. Set the output power of the 266nm Q-switched laser to 8mW, and adjust the beam spot size to a power density of 3W cm⁻¹ using the lens group. -2 By setting the output time of the 266nm Q-switched laser to 25s, modified half-metal MoTe2 can be obtained. Figure 6 );

[0114] S9: Nickel / gold electrodes are prepared on a silicon dioxide substrate using photolithography and thermal evaporation techniques to obtain substrate I, wherein the nickel electrode is located at the bottom and the gold electrode is located at the top, and the thicknesses of the chromium electrode and the gold electrode are 10 nm and 50 nm, respectively.

[0115] S10: By combining the modified MoTe2 nanocrystals described in S8 with the substrate I described in S9, a photodetector can be obtained. The specific implementation method is as follows:

[0116] S101: Repeat S1-S5 to obtain MoTe2 nanocrystals on PDMS film;

[0117] S102: Place the silicon wafer with metal electrodes described in S9 on the vacuum adsorption stage and turn on the vacuum adsorption function to fix the silicon wafer.

[0118] S103: Using a metallographic microscope, align the PDMS film described in S101 with the electrode position described in S102, slowly attach the film and the electrode, and set the heating temperature to 70 degrees and the heating time to 20 minutes.

[0119] S104: Turn off the heating switch, slowly lift the PDMS film, and fix the MoTe2 nanocrystals above the electrode described in S102;

[0120] S105: The modified photodetector can be obtained by irradiating the MoTe2 nanocrystal on the substrate described in S104 with a 266nm Q-switched laser.

[0121] The electrical conductivity of the prepared modified half-metal MoTe2 photodetector was tested. After connecting the two ends of the electrode to a conductive probe using a microprobe stage, a current-voltage test was performed using a source meter. The test results are as follows: Figure 7 As shown, the IV characteristic curve of the unmodified half-metal MoTe2 exhibits good ohmic contact characteristics, while the IV characteristic curve of the modified half-metal MoTe2 exhibits Schottky contact characteristics, indicating that ultraviolet laser induction effectively improves photocurrent and reduces dark current.

[0122] The prepared modified half-metal MoTe2 ultraviolet-terahertz broadband detector was subjected to photoelectric information detection under 266nm and 808nm laser light, respectively. The photocurrent test results are as follows: Figure 8 , Figure 9 As shown, the dark current of the modified half-metal MoTe2 detector is two orders of magnitude lower.

[0123] In comparison, this invention tested a semi-metallic MoTe2 detector (detector 2) before ultraviolet laser irradiation. The only difference between detector 2 and the photodetector proposed in this patent is that detector 2 was not irradiated with ultraviolet laser. Photoelectric information detection was performed on detector 2 under 808nm and 1064nm lasers, respectively. The photocurrent test results are as follows: Figure 10 and Figure 11 As shown, detector 2 can only achieve photoelectric response in the 808nm-1064nm range, which is much smaller than the operating wavelength range of the photodetector proposed in this invention (266nm-1.67nm). Figure 7 As shown, since detector 2 was not irradiated by ultraviolet laser, the functional layer MoTe2 nanocrystal I could not be modified. Therefore, the dark current of detector 2 is two orders of magnitude higher than that of the photodetector proposed in this invention.

[0124] As can be seen from the above technical solution, the present invention has the following significant features:

[0125] 1. High-quality fabrication of nanocrystals: Through precisely controlled mechanical exfoliation techniques, parameters such as exfoliation force, angle, and speed can be accurately controlled to obtain high-quality MoTe2 nanocrystals, meeting diverse application scenarios and device design requirements. Furthermore, by combining these techniques with other processes, various complex heterostructures and devices can be fabricated.

[0126] 2. Effective material modification: MoTe2 nanocrystals are modified by irradiation with a 266nm Q-switched laser, introducing new electronic states or changing the surface states of the material. This can effectively control the photoelectric properties of the material, providing a basis for realizing specific photoelectric applications.

[0127] 3. Integration and miniaturization of optoelectronic devices: Through precise photolithography and micromechanical transfer technology, miniature polarization photodetectors can be integrated on silicon substrates, which is conducive to the high integration of micro and nano devices. This is especially important for portable and miniaturized optoelectronic devices.

[0128] 4. Controllability and repeatability of the preparation process: A relatively simple and controllable preparation method is provided, which can precisely control the composition and thickness of the MoTe2 film, thereby achieving the regulation of its performance; due to the relative stability of the process, the preparation process has good repeatability and is suitable for large-scale production.

[0129] 5. Expanded application prospects: The development of this technology not only opens up new avenues for the application of MoTe2 materials in the optoelectronic field, but also provides a new modification and application approach for similar semi-metallic materials.

[0130] 6. Performance optimization and control: By changing the parameters of laser irradiation, such as wavelength, power and irradiation time, the properties of materials can be more precisely controlled, further improving the performance of photodetectors, such as sensitivity and response speed.

[0131] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for modifying the half-metal MoTe2, characterized in that, Includes the following steps: S1: Lay the half-metallic MoTe2 crystal flat on 3M tape and press it down; S2: Repeatedly tear and stick the 3M tape 4-6 times, and observe it under a microscope to confirm that it meets the set thickness and area requirements, and obtain thin-layer MoTe2 crystal I; S3: Adhere the 8mm×8mm PDMS film onto the glass slide; S4: Align the 3M tape in S2 with the PDMS film in S3 and stick it on. Take a picture under a microscope to record the relative position of the nanosheet with the surrounding environment and hold it with an eraser. S5: Tear off the 3M tape to obtain MoTe2 nanocrystals I on the PDMS film, and fix the PDMS film with MoTe2 crystals on the robotic arm above the substrate stage; S6: Fine-tune the z-axis to lower the robotic arm until the PDMS film in S5 is firmly attached to the silicon wafer containing 400nm thick SiO2, and heat the metal clamp of the robotic arm. S7: Stop heating, lift the robotic arm, remove the substrate, and obtain MoTe2 nanocrystals I on the Si / SiO2 substrate to complete the transfer; S8: MoTe2 nanocrystal I on the substrate in S7 was irradiated with a 266nm Q-switched laser to obtain modified half-metal MoTe2.

2. The method for modifying the half-metal MoTe2 as described in claim 1, characterized in that, In step S1, the half-metal MoTe2 crystal is synthesized by chemical vapor deposition, the 3M tape is 3M8153LE transfer film, and the pressing time is 20 seconds.

3. The method for modifying the half-metal MoTe2 as described in claim 2, characterized in that, In step S2, the thickness of MoTe2 crystal I is 50nm-70nm; in step S3, the PDMS film is Gel-pak PF-3-x4.

4. The method for modifying the half-metal MoTe2 as described in claim 3, characterized in that, In step S4, the time for holding the film with rubber is 20 hours; the thickness of the MoTe2 nanocrystal I obtained on the PDMS film is 50nm-70nm.

5. The method for modifying the half-metal MoTe2 as described in claim 4, characterized in that, In step S6, the heating temperature is 70 degrees Celsius and the heating time is 20 minutes.

6. The method for modifying the half-metal MoTe2 as described in claim 5, characterized in that, Step S8 includes the following sub-steps: S81: The position of the crystal in S7 is adjusted using a three-dimensional adjustment frame to ensure that the crystal is within the coverage area of ​​the light spot; S82: Set the output power of the 266nm Q-switched laser to 8mW, and adjust the spot size to a power density of 3W cm⁻¹ using the lens group. -2 ; S83: Set the output time of the 266nm Q-switched laser to 25s.

7. A photodetector based on modified half-metal MoTe2, characterized in that, The structure comprises MoTe2 nanocrystals I modified by the modification method described in claim 6, source metal electrode II, drain metal electrode III, SiO2 insulating layer IV, and Si substrate V, which are connected sequentially from top to bottom.

8. A method for fabricating a photodetector based on modified half-metal MoTe2, characterized in that, Includes the following steps: Step 21: Nickel / gold source metal electrode II and nickel / gold drain metal electrode III are fabricated on Si substrate V and silicon dioxide substrate IV using photolithography and thermal evaporation techniques to obtain substrate I; Step 22: Combine the MoTe2 nanocrystal I modified by the modification method described in claim 6 with the substrate I from step 21 to obtain a photodetector.

9. The method for fabricating a photodetector as described in claim 8, characterized in that, In step 21, the thicknesses of the nickel electrode and the gold electrode are 10 nm and 50 nm, respectively.

10. The method for fabricating a photodetector as described in claim 9, characterized in that, Step 22 includes the following sub-steps: Step 221: Obtain MoTe2 nanocrystals I on PDMS film; Step 222: Place substrate I from step 21 on the vacuum adsorption stage and turn on the vacuum adsorption function to fix substrate I. Step 223: Using a metallographic microscope, align the PDMS film from step 21 with the positions of source metal electrode II and drain metal electrode III from step 22, attach the film and source metal electrode II and drain metal electrode III tightly, and set the heating temperature to 70 degrees and the heating time to 20 minutes. Step 224: Turn off the heating switch, lift the PDMS film, and fix the MoTe2 nanocrystal I above the source metal electrode II and drain metal electrode III in step 22; Step 225: Irradiate the MoTe2 nanocrystal I on the substrate from step 224 with a 266nm Q-switched laser to obtain the modified photodetector.

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