Two-dimensional metal material for ultraviolet photoelectric detector and preparation method of two-dimensional metal material

Abstract

The invention relates to a two-dimensional metal material for an ultraviolet photoelectric detector and a preparation method of the two-dimensional metal material, and belongs to the technical field of detector preparation, a sapphire substrate is activated through high-activity particles through plasma treatment, hydroxyl active sites are introduced, a clean interface foundation is laid for heteroepitaxial growth of an ultra-wide forbidden band Ga2O3 film, and the performance of the detector is improved. The method comprises the following steps: performing chemical vapor deposition on Ga2O3 to ensure the specific absorption capacity of Ga2O3 to ultraviolet light, annealing in a mixed atmosphere after chemical vapor deposition, repairing the oxygen vacancy defect of a Ga2O3 film by using the high activity of ozone, improving the crystallization quality, effectively reducing dark current noise, and performing in-situ growth of a WSe2 layer in a high vacuum environment through a pulse laser deposition technology to form a van der Waals heterojunction without lattice mismatch. And an efficient carrier separation channel can be constructed by virtue of energy level matching of WSe2 and Ga2O3, so that the problem that ultraviolet absorption and carrier transmission are difficult to consider by virtue of a single material is solved, and the light response capability of the device is remarkably enhanced.

Description

A two-dimensional metallic material for ultraviolet photodetectors and its preparation method Technical Field

[0001] This invention belongs to the field of detector fabrication technology, and relates to a two-dimensional metal material for ultraviolet photodetectors and its fabrication method. Background Technology

[0002] Ultraviolet (UV) photodetectors are core devices in the field of optoelectronic information, possessing irreplaceable application value in scenarios such as fire early warning, environmental monitoring, and precision detection. Two-dimensional (2D) metallic materials, with their atomically thin structural features and unique photoelectric properties, have become a key direction for overcoming the performance bottlenecks of traditional UV detection materials. Due to their ultra-high carrier mobility, large specific surface area, tunable electronic structure, and light absorption characteristics matched to the UV band, 2D metallic materials can effectively improve the photoelectric conversion efficiency of detectors. Their layered van der Waals structure can also achieve lattice-mismatch-free heterostructure construction, providing a new path for optimizing interface charge transport and reducing dark current, making them ideal core materials for high-performance UV photodetectors.

[0003] Chinese invention patent application CN115498058A discloses a broadband photodetector based on two-dimensional magnetic materials and its fabrication method. The detector is prepared using silicon dioxide as a supporting substrate, a two-dimensional magnetic single-crystal thin film as a channel layer, a metal electrode as an electrode layer, and hBN as an encapsulation layer. The two-dimensional magnetic single-crystal thin film is obtained by mechanically exfoliating a two-dimensional magnetic single-crystal material. The broadband photodetector has a visible light response time of 121.7 ms and a responsivity of 26.1 A / W. By exploring the interaction between the magnetic and photoelectric properties of two-dimensional magnetic materials, it has great potential for developing advanced spin-optoelectronic device applications.

[0004] The photodetector in the above scheme is not suitable for photodetection in the ultraviolet band. The two-dimensional magnetic material it uses is a broadband response material, which cannot achieve selective absorption of ultraviolet light. It is difficult to efficiently capture ultraviolet photons and is easily interfered with by background light such as visible light and infrared light, resulting in low specificity and signal-to-noise ratio of ultraviolet detection. Summary of the Invention

[0005] The purpose of this invention is to provide a two-dimensional metal material for ultraviolet photodetectors and its preparation method. By depositing Ga2O3 thin films and WSe2 thin films on a sapphire substrate through plasma treatment, and then sputtering a Ti / Au layer, the material's photoresponsivity and stability are improved.

[0006] The objective of this invention can be achieved through the following technical solution: A method for preparing a two-dimensional metal material for an ultraviolet photodetector, comprising the following steps: Step 1: Ultrasonic cleaning and drying of a sapphire substrate, followed by plasma treatment for 25-35 seconds to obtain a plasma-treated sapphire substrate.

[0007] Step 2: Deposit a Ga2O3 thin film on a plasma-treated sapphire substrate using chemical vapor deposition, followed by annealing to obtain a substrate containing a Ga2O3 thin film.

[0008] Step 3: Deposit a WSe2 film on a substrate containing a Ga2O3 film using a pulsed laser deposition system to obtain a substrate containing a layered WSe2 film.

[0009] Step 4: First, a Ti layer is sputtered onto a substrate containing a layered WSe2 thin film using electron beam sputtering technology, and then an Au layer is sputtered onto it to obtain a two-dimensional metal material for ultraviolet photodetectors.

[0010] Furthermore, the plasma treatment parameters are: discharge voltage 22-26 kV, discharge frequency 10-10.5 kHz, working gas argon, and gas flow rate 70-90 cm³ / h. 3 / s, humidity 55-65%, plasma jet long axis perpendicular to substrate treatment surface, nozzle 5-7mm from substrate surface.

[0011] The combination of discharge voltage of 22-26kV and frequency of 10-10.5kHz can generate highly active particles with moderate energy, which is sufficient to activate the substrate surface while avoiding damage to the substrate caused by high-energy particle bombardment. Argon gas can maintain a stable jet morphology to ensure uniform processing in all areas of the substrate.

[0012] Furthermore, the specific preparation process of the substrate containing Ga2O3 thin film is as follows: the temperature in the chemical vapor deposition reaction chamber is set to 740-770℃ and the pressure to 3-5KPa. Gallium source and oxygen source are introduced, and argon gas is used as the carrier gas. Deposition is carried out for 1-2 hours. Under mixed atmosphere, it is annealed at a temperature of 580-620℃ for 55-65 minutes to obtain the substrate containing Ga2O3 thin film.

[0013] The temperature range is suitable for heteroepitaxial growth of Ga2O3 on sapphire substrates, ensuring sufficient decomposition of the precursor while avoiding excessive thermal stress between the substrate and the film due to high temperature. The 3-5 kPa pressure can balance the film deposition rate and uniformity. Argon gas, as an inert carrier gas, can stably transport the precursor and remove impurities from the reaction chamber. The 1-2 h deposition time can precisely control the film thickness to meet the requirements of ultraviolet absorption. The control of annealing temperature and time can repair lattice defects and oxygen vacancies without damaging the film structure, thereby improving stability.

[0014] Furthermore, the gallium source flux is 470-510 sccm. This flux ensures a sufficient Ga source, thereby improving the photoelectric conversion efficiency of the thin film.

[0015] Furthermore, the oxygen source flow rate is 6200-6800 sccm. This flow rate can meet the oxygen atom requirements for Ga2O3 growth while avoiding excessive oxygen atoms that could lead to film over-oxidation, thus ensuring the uniformity of the film.

[0016] Furthermore, the gallium source is either triethylgallium or trimethylgallium.

[0017] Furthermore, the oxygen source is either nitrous oxide or oxygen.

[0018] Furthermore, the argon flow rate is 2300-2700 sccm. This flow rate ensures stable gas flow within the reaction chamber, uniformly delivering the precursor to the substrate surface while promptly removing reaction byproducts to prevent byproduct residues from contaminating the film and improving film surface smoothness.

[0019] Furthermore, the volume ratio of oxygen to ozone in the mixed atmosphere is 9-8:1-2.

[0020] By using ozone's high activity to efficiently repair oxygen vacancies in Ga2O3 films while avoiding excessive ozone leading to over-oxidation of the film surface, this ratio balances defect repair efficiency and film stability, resulting in a significant reduction in dark current of the film after annealing.

[0021] Furthermore, the specific preparation process of the substrate containing the layered WSe2 thin film is as follows: The substrate containing the Ga2O3 thin film is fixed on the target holder, the WSe2 target is installed, and then placed in the pulsed laser deposition cavity. A vacuum operation is performed, and the temperature is raised to 390-410℃, achieving a vacuum degree of 5×10⁻⁶. -6 -5×10 -5 Pa, deposited for 8-12 min, and naturally cooled to room temperature to obtain a substrate containing a layered WSe2 thin film.

[0022] High vacuum can eliminate impurities such as oxygen and water vapor in the cavity, preventing WSe2 film from being oxidized during growth. The temperature of 390-410℃ is suitable for the layered growth of WSe2, ensuring the quality of film crystallization while avoiding diffusion at the Ga2O3 / WSe2 interface caused by high temperature.

[0023] Furthermore, the parameters for pulsed laser deposition are: pulse frequency 1.8-2.2Hz, laser power 120-140mJ, and voltage 18-22kV.

[0024] A pulse frequency of 1.8-2.2Hz can balance the deposition rate and crystal quality of WSe2 thin films. Too high a frequency can easily lead to target particle agglomeration, while too low a frequency will result in low deposition efficiency. The laser power can ensure that the target is fully sputtered and the particle energy is moderate, avoiding damage to the Ga2O3 underlayer due to excessive energy. The voltage range ensures stable laser output, achieving uniform and high-quality growth of WSe2 thin films.

[0025] Furthermore, the specific preparation process of the two-dimensional metallic material used in the ultraviolet photodetector is as follows: A substrate containing a layered WSe2 thin film is fixed on the target holder and installed in a specific position within the cavity. Titanium particles and gold particles are placed in a double crucible, pre-evacuated to 0.8-1.2 Pa, and then evacuated to 3 × 10⁻⁶ Pa. -5 -8×10 -6 At a pressure of Pa for 8-12 min, a Ti layer is first deposited, the substrate is heated to 140-160℃, and the sputtering rate is 0.25-0.35 nm / s. Then, an Au layer is deposited, the substrate temperature is maintained, and the sputtering rate is 0.12-0.18 nm / s. The temperature is then raised to 190-210℃ in an argon atmosphere and held for 25-35 min. The temperature is then lowered to room temperature to obtain a two-dimensional metallic material for ultraviolet photodetectors.

[0026] A substrate temperature of 140-160℃ can promote the chemical bonding between the Ti layer and WSe2. The sputtering speed of the Ti layer maintains the interlayer adhesion, the sputtering speed of the Au layer improves the surface smoothness, and annealing in an argon atmosphere at 190-210℃ can repair the interface defects between the electrode and the thin film. The holding time ensures the stability of the interface structure.

[0027] Furthermore, the thickness of the Ti layer is 19-21 nm.

[0028] This thickness ensures sufficient Ti-Se chemical bonding with the WSe2 surface for stable ohmic contact, while avoiding ultraviolet light absorption loss or prolonged carrier transport paths due to excessive Ti layer thickness, thus balancing contact stability and photoelectric detection efficiency.

[0029] Furthermore, the Au layer thickness is 58-62 nm.

[0030] This thickness reduces carrier transport losses while avoiding excessive electrode stress or increased costs due to excessive thickness, thus balancing device performance and practicality.

[0031] The present invention also provides a two-dimensional metal material for ultraviolet photodetectors, which is obtained by ultrasonic cleaning, plasma treatment, chemical vapor deposition of Ga2O3 thin film, pulsed laser deposition of WSe2 thin film on sapphire substrate, and then sputtering Ti layer first and Au layer on electron beam sputtering.

[0032] The beneficial effects of this invention are as follows: 1. This invention activates the sapphire substrate with highly active particles through plasma treatment, introducing hydroxyl active sites to lay a clean interface foundation for the heteroepitaxial growth of ultrawide bandgap Ga2O3 thin films, ensuring the specific absorption capacity of Ga2O3 for ultraviolet light. After chemical vapor deposition, mixed atmosphere annealing is used to repair oxygen vacancy defects in the Ga2O3 thin film by utilizing the high activity of ozone, improving crystal quality and effectively reducing dark current noise. Then, WSe2 layer is grown in situ in a high vacuum environment by pulsed laser deposition technology to form a van der Waals heterojunction without lattice mismatch. With the energy level matching between WSe2 and Ga2O3, a highly efficient carrier separation channel can be constructed, solving the problem that a single material cannot simultaneously achieve ultraviolet absorption and carrier transport, significantly enhancing the photoresponse capability of the device. At the same time, the Ti / Au double-layer electrode achieves ohmic contact with the WSe2 surface through chemical bonding, reducing carrier transport loss.

[0033] 2. After the two-dimensional metal materials prepared in this invention are assembled into a detector, the ultra-wide bandgap of Ga2O3 endows the device with excellent ultraviolet selectivity and effectively shields background light interference. The two-dimensional layered structure of WSe2 shortens the carrier transport path and reduces transport loss. The ohmic contact of the Ti / Au electrode accelerates carrier collection. The three factors work together to reduce the probability of carrier recombination and achieve fast response. In addition, plasma treatment, annealing and other steps effectively reduce internal defects in the material and reduce dark current noise. The high vacuum growth environment avoids oxidation of the WSe2 film and ensures the cleanliness of the heterojunction interface. The chemical bonding between the Ti layer and WSe2 and the argon atmosphere post-treatment improve the long-term working stability of the device and avoid performance degradation during long-term use.

[0034] 3. This invention solves the problems of weak interface bonding and lattice mismatch in traditional heterojunction devices through a refined interface control process. The van der Waals heterojunction formed by Ga2O3 and WSe2 has no lattice mismatch stress and a low interface state density, ensuring smooth carrier transport. The chemical bonding between the Ti layer and WSe2 replaces physical adhesion, enhancing the bonding stability between the electrode and the functional layer. In addition, a closed-loop control is formed from substrate activation to thin film deposition, and then to electrode preparation and annealing, effectively reducing interface contamination and defects, and ensuring that the device can still work stably in complex environments. Detailed Implementation

[0035] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention is provided in conjunction with preferred embodiments.

[0036] Example 1: This example provides a two-dimensional metallic material for an ultraviolet photodetector, prepared through the following steps: S1: The sapphire substrate is ultrasonically cleaned for 5 minutes using acetone, ethanol, and deionized water sequentially, then baked at 90°C for 35 minutes, and treated in an argon low-temperature atmospheric pressure plasma jet generator for 30 seconds. The plasma treatment parameters are: discharge voltage 24kV, discharge frequency 10.2kHz, working gas argon, and gas flow rate 80cm³. 3 / s, humidity 60%, plasma jet long axis perpendicular to substrate treatment surface, nozzle 6mm from substrate surface, to obtain plasma-treated sapphire substrate.

[0037] S2: A Ga2O3 thin film was deposited on a plasma-treated sapphire substrate using chemical vapor deposition (CVD). The growth environment conditions in the CVD reaction chamber were set at a temperature of 755℃ and a pressure of 4 kPa. Triethylgallium (purity ≥99.99%, TEGa, purchased from Jiuyi Materials Technology (Wuhan) Co., Ltd.) and nitrous oxide (purity ≥99.99%) were introduced as the Ga source and O source for Ga2O3 growth, respectively. The flow rate of triethylgallium was 490 sccm, and the flow rate of nitrous oxide was 6500 sccm. High-purity argon was used as the carrier gas with a flow rate of 2500 sccm. The deposition time was 1.5 h. The substrate was annealed at 600℃ for 60 min in a mixed atmosphere of oxygen and ozone (volume ratio of 8.5:1.5) to obtain a substrate containing a Ga2O3 thin film.

[0038] S3: The substrate containing the Ga2O3 thin film is fixed to the target holder using a titanium alloy metal clamp. After the WSe2 target is installed, it is placed into the pulsed laser deposition cavity. After closing the cavity, the airtightness of the pulsed laser deposition system is checked. A vacuum operation is performed, and the temperature is increased from room temperature to 400℃ in 30 minutes, with a vacuum degree of 2.75×10⁻⁶. -5 Pa, pulse frequency of 2.0 Hz, laser power of 130 mJ, deposition time of 10 min, voltage of 20 kV. After deposition is completed, the laser is turned off, the PLD temperature control module is turned off to allow the substrate to cool down, and it is allowed to cool naturally to room temperature. The sample is then removed to obtain a substrate containing a layered WSe2 thin film.

[0039] S4: Fix the substrate containing the layered WSe2 thin film onto the electron beam sputtering target holder and install the sample holder in a specific position within the chamber. Place titanium particles (99.99% purity) and gold particles (99.99% purity) into the double crucible (Ti on top, Au on the bottom) and close the chamber door. After checking the chamber's airtightness, turn on the mechanical pump and pre-evacuate to 1.0 Pa. Then start the molecular pump and evacuate to 5.5 × 10⁻⁶ Pa. -6At a pressure of 10 min, electron beam evaporation was initiated. First, a Ti layer was deposited. The substrate was heated to 150°C, and the sputtering rate was controlled at 0.3 nm / s. The Ti layer was stopped after monitoring the thickness to 20 nm using a film thickness gauge. Then, an Au layer was deposited. The substrate temperature was maintained at 150°C, and the sputtering rate was controlled at 0.15 nm / s. The gold layer thickness was 60 nm. The sputtering process was stopped, and argon gas was introduced into the cavity at a flow rate of 50 sccm. The temperature was raised to 200°C and held for 30 min. The temperature was then lowered to room temperature at a rate of 5°C / min to obtain a two-dimensional metallic material for ultraviolet photodetectors.

[0040] Example 2: This example provides a two-dimensional metallic material for an ultraviolet photodetector, prepared through the following steps: S1: The sapphire substrate is ultrasonically cleaned with acetone, ethanol, and deionized water sequentially for 4 minutes, then baked at 80°C for 30 minutes, and then treated in an argon low-temperature atmospheric pressure plasma jet generator for 25 seconds. The plasma treatment parameters are: discharge voltage 22kV, discharge frequency 10kHz, working gas argon, and gas flow rate 70cm³. 3 / s, humidity 55%, plasma jet long axis perpendicular to substrate treatment surface, nozzle 5mm from substrate surface, to obtain plasma-treated sapphire substrate.

[0041] S2: A Ga2O3 thin film was deposited on a plasma-treated sapphire substrate using chemical vapor deposition (CVD). The growth environment conditions in the CVD reaction chamber were set at a temperature of 740℃ and a pressure of 3 kPa. Triethylgallium (purity ≥99.99%, TEGa, purchased from Jiuyi Materials Technology (Wuhan) Co., Ltd.) and nitrous oxide (purity ≥99.99%) were introduced as the Ga source and O source for Ga2O3 growth, respectively. The flow rate of triethylgallium was 470 sccm, and the flow rate of nitrous oxide was 6200 sccm. High-purity argon was used as the carrier gas with a flow rate of 2300 sccm. The deposition time was 1 h. The substrate containing the Ga2O3 thin film was obtained by annealing at 580℃ for 55 min in a mixed atmosphere of oxygen and ozone (volume ratio of 9:1).

[0042] S3: The substrate containing the Ga2O3 thin film is fixed to the target holder using a titanium alloy metal clamp. After the WSe2 target is installed, it is placed into the pulsed laser deposition cavity. After closing the cavity, the airtightness of the pulsed laser deposition system is checked. A vacuum operation is performed, and the temperature is increased from room temperature to 390℃ in 25 minutes, with a vacuum degree of 5×10⁻⁶. -6 Pa, pulse frequency of 1.8 Hz, laser power of 120 mJ, deposition time of 8 min, voltage of 18 kV. After deposition is completed, the laser is turned off, the PLD temperature control module is turned off to allow the substrate to cool down, and it is allowed to cool naturally to room temperature. The sample is then removed to obtain a substrate containing a layered WSe2 thin film.

[0043] S4: Fix the substrate containing the layered WSe2 thin film onto the electron beam sputtering target holder and install the sample holder in a specific position within the chamber. Place titanium particles (99.99% purity) and gold particles (99.99% purity) into the double crucible (Ti on top, Au on the bottom) and close the chamber door. After checking the chamber's airtightness, turn on the mechanical pump and pre-evacuate to 0.8 Pa. Then start the molecular pump and evacuate to 3 × 10⁻⁶ Pa. -5 At a pressure of 8 Pa, electron beam evaporation was initiated. First, a Ti layer was deposited. The substrate was heated to 140°C, and the sputtering rate was controlled at 0.25 nm / s. The Ti layer was stopped after monitoring the thickness of the film to 19 nm. Then, an Au layer was deposited. The substrate temperature was maintained at 140°C, and the sputtering rate was controlled at 0.12 nm / s. The gold layer thickness was 58 nm. The sputtering process was stopped, and argon gas was introduced into the cavity at a flow rate of 45 sccm. The temperature was raised to 190°C and held for 25 min. The temperature was then lowered to room temperature at a rate of 5°C / min to obtain a two-dimensional metallic material for ultraviolet photodetectors.

[0044] Example 3: This example provides a two-dimensional metallic material for an ultraviolet photodetector, prepared through the following steps: S1: The sapphire substrate is ultrasonically cleaned for 6 minutes using acetone, ethanol, and deionized water sequentially, then baked at 100°C for 40 minutes, and treated in an argon low-temperature atmospheric pressure plasma jet generator for 35 seconds. The plasma treatment parameters are: discharge voltage 26kV, discharge frequency 10.5kHz, working gas argon, and gas flow rate 90cm³. 3 / s, humidity 65%, plasma jet long axis perpendicular to substrate treatment surface, nozzle 7mm from substrate surface, to obtain plasma-treated sapphire substrate.

[0045] S2: A Ga2O3 thin film was deposited on a plasma-treated sapphire substrate using chemical vapor deposition (CVD). The growth environment conditions in the CVD reaction chamber were set at a temperature of 770℃ and a pressure of 5 kPa. Triethylgallium (purity ≥99.99%, TEGa, purchased from Jiuyi Materials Technology (Wuhan) Co., Ltd.) and nitrous oxide (purity ≥99.99%) were introduced as the Ga source and O source for Ga2O3 growth, respectively. The flow rate of triethylgallium was 510 sccm, and the flow rate of nitrous oxide was 6800 sccm. High-purity argon was used as the carrier gas with a flow rate of 2700 sccm. The deposition time was 2 h. The substrate containing the Ga2O3 thin film was obtained by annealing at 620℃ for 65 min in a mixed atmosphere of oxygen and ozone (volume ratio of 8:2).

[0046] S3: The substrate containing the Ga2O3 thin film is fixed to the target holder using a titanium alloy metal clamp. After the WSe2 target is installed, it is placed into the pulsed laser deposition cavity. After closing the cavity, the airtightness of the pulsed laser deposition system is checked. A vacuum operation is performed, and the temperature is increased from room temperature to 410℃ in 35 minutes, with a vacuum degree of 5×10⁻⁶. -5 Pa, pulse frequency of 2.2Hz, laser power of 140mJ, deposition time of 12min, voltage of 22kV. After deposition is completed, the laser is turned off, the PLD temperature control module is turned off to allow the substrate to cool down, and it is allowed to cool naturally to room temperature. The sample is then removed to obtain a substrate containing a layered WSe2 thin film.

[0047] S4: Fix the substrate containing the layered WSe2 thin film onto the electron beam sputtering target holder and install the sample holder in a specific position within the chamber. Place titanium particles (99.99% purity) and gold particles (99.99% purity) into the double crucible (Ti on top, Au on the bottom) and close the chamber door. After checking the chamber's airtightness, turn on the mechanical pump and pre-evacuate to 1.2 Pa. Then start the molecular pump and evacuate to 8 × 10⁻⁶ Pa. -6 At a pressure of 12 min, electron beam evaporation was initiated. First, a Ti layer was deposited. The substrate was heated to 160°C, and the sputtering rate was controlled at 0.35 nm / s. The Ti layer was stopped after monitoring the thickness of the film to 21 nm. Then, an Au layer was deposited. The substrate temperature was maintained at 160°C, and the sputtering rate was controlled at 0.18 nm / s. The gold layer thickness was 62 nm. The sputtering process was stopped, and argon gas was introduced into the cavity at a flow rate of 55 sccm. The temperature was raised to 210°C and held for 35 min. The temperature was then lowered to room temperature at a rate of 5°C / min to obtain a two-dimensional metallic material for ultraviolet photodetectors.

[0048] Example 4: This example provides a two-dimensional metal material for an ultraviolet photodetector. The difference from Example 1 is that trimethylgallium is used instead of triethylgallium in step S2.

[0049] Example 5: This example provides a two-dimensional metal material for ultraviolet photodetectors. The difference from Example 1 is that oxygen is used instead of nitrous oxide in step S2.

[0050] Comparative Example 1: This comparative example provides a two-dimensional metal material for an ultraviolet photodetector. The difference from Example 1 is that step S1 is omitted, and a sapphire substrate is used instead of plasma-treated sapphire substrate in step S2.

[0051] Comparative Example 2: This comparative example provides a two-dimensional metal material for an ultraviolet photodetector. The difference from Example 1 is that step S2 is omitted, and in step S3, the plasma-treated sapphire substrate prepared in step S1 is used instead of the substrate containing the Ga2O3 thin film.

[0052] Comparative Example 3: This comparative example provides a two-dimensional metal material for an ultraviolet photodetector. The difference from Example 1 is that step S3 is omitted, and in step S4, the substrate containing a Ga2O3 thin film prepared in step S2 is used instead of the substrate containing a layered WSe2 thin film.

[0053] Comparative Example 4: This comparative example provides a two-dimensional metallic material for an ultraviolet photodetector. The difference from Example 1 is that Ti layer deposition is not performed in step S4.

[0054] The two-dimensional metallic materials for ultraviolet photodetectors prepared in Examples 1-5 and Comparative Examples 1-4 were assembled into ultraviolet photodetectors, and their performance was tested. Test indicators: photoresponsivity (R), dark current (Ig). dark ), response time (τ) r / τ d Rise / fall time and long-term stability (response decay rate after 1000 hours of continuous operation).

[0055] Test conditions: A 5V bias voltage was applied to the detector, and the ultraviolet light power density was 300μW / cm². 2 (254nm), visible light power density 300μW / cm² 2 (400nm), room temperature (25±5℃), humidity 55±5%RH standard environment. The testing equipment included a semiconductor analyzer and a laser pulse transient response testing system.

[0056] Photoresponsivity (R) generally refers to the photocurrent responsivity of a photodetector, representing the photocurrent generated by the detector under excitation of unit incident light power. It represents the photoelectric conversion capability of the photodetector, and the calculation formula is as follows: R = I light -I dark / (PS); where P is the incident light power density and S is the effective illumination area of ​​the detector. The larger the R of the photodetector, the more effectively it can convert optical signals into electrical signals.

[0057] Dark current (I dark The current value is measured when a bias voltage is applied to the ultraviolet photodetector in the dark state, i.e., under conditions of no light. For the ultraviolet photodetector, I... dark The smaller the value, the less background noise the detector has and the lower the power consumption during standby.

[0058] Photocurrent (I photo The photocurrent (I0) refers to the photoresponse current generated when a photodetector is illuminated. It is typically measured by the current value (I0) obtained under illumination. light Subtracting the dark current value, we get the result using the following formula: I photo =I light -Idark For ultraviolet photodetectors, when exposed to solar-blind ultraviolet light, the device's I... photo The larger the better, so that the device's Ig is more efficient when exposed to light of other wavelengths. photo The smaller the better, as this indicates that the device has a strong anti-interference capability.

[0059] Response time is the time it takes for a photodetector to react to an incident light signal. Response time is typically divided into rise time (τ). r ) and descent time (τ) d The photodetector consists of two parts. Rise time refers to the time required for the output photocurrent signal to rise from its initial state to a steady state when the photodetector is illuminated, while fall time refers to the time required for the output photocurrent signal to fall from its steady state to its initial state when the illumination stops.

[0060] The test results are shown in the table below: Table 1 Performance Test Overview As shown in Table 1, the photoresponsivity of Examples 1-5 is greater than that of Comparative Examples 1-4. This may be because the energy level matching between Ga2O3 and WSe2 promotes efficient separation of photogenerated carriers, and the Ti-Se chemical bond formed between the Ti layer and WSe2 achieves low-resistance contact, reducing carrier transport loss, thus resulting in higher photoresponsivity.

[0061] As shown in Table 1, the I values ​​of Examples 1-5 are... dark The lower density compared to Comparative Examples 1-4 may be due to the removal of substrate impurities through plasma treatment, the repair of Ga2O3 oxygen vacancies through annealing, and the reduction of WSe2 film oxidation through high-vacuum deposition, resulting in a low interface state density.

[0062] As shown in Table 1, the response time τ of Examples 1-5 r τ d The values ​​are all smaller than those of Comparative Examples 1-4, which may be because the two-dimensional structure of the WSe2 layer shortens the carrier transport path, the ohmic contact of the Ti / Au double-layer electrode accelerates carrier collection, and there is no lattice mismatch at the heterojunction interface.

[0063] As shown in Table 1, the stability decay rate of Examples 1-5 after 1000h is less than that of Comparative Examples 1-4. This may be because the chemical bonding between the Ti layer and WSe2 enhances the interface stability, the high-purity raw materials and argon atmosphere annealing reduce electrode oxidation, and the van der Waals heterojunction structure of Ga2O3 and WSe2 is robust.

[0064] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a two-dimensional metallic material for an ultraviolet photodetector, characterized in that, The process includes the following steps: Step 1: Ultrasonic cleaning and drying of the sapphire substrate, followed by plasma treatment for 25-35 seconds to obtain a plasma-treated sapphire substrate; Step 2: Deposition of a Ga2O3 thin film on the plasma-treated sapphire substrate using chemical vapor deposition, followed by annealing to obtain a substrate containing a Ga2O3 thin film; Step 3: Deposition of a WSe2 thin film on the Ga2O3 thin film substrate using a pulsed laser deposition system to obtain a substrate containing a layered WSe2 thin film; Step 4: Sputtering a Ti layer onto the substrate containing the layered WSe2 thin film using electron beam sputtering, followed by sputtering an Au layer to obtain a two-dimensional metal material for ultraviolet photodetectors.

2. The method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 1, characterized in that, The parameters for plasma treatment in step one are: discharge voltage of 22-26 kV, discharge frequency of 10-10.5 kHz, working gas of argon, and gas flow rate of 70-90 cm³ / h. 3 / s, humidity 55-65%, plasma jet long axis perpendicular to substrate treatment surface, nozzle 5-7mm from substrate surface.

3. The method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 1, characterized in that, The specific preparation process of the substrate containing Ga2O3 thin film in step two is as follows: The temperature in the chemical vapor deposition reaction chamber is set to 740-770℃ and the pressure to 3-5KPa. Gallium source and oxygen source are introduced, and argon gas is used as the carrier gas. Deposition is carried out for 1-2 hours. Under the mixed atmosphere, it is annealed at a temperature of 580-620℃ for 55-65 minutes to obtain the substrate containing Ga2O3 thin film.

4. The method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 3, characterized in that, The flow rate of the gallium source is 470-510 sccm, the flow rate of the oxygen source is 6200-6800 sccm, and the flow rate of the argon gas is 2300-2700 sccm; the gallium source is either triethylgallium or trimethylgallium; and the oxygen source is either nitrous oxide or oxygen.

5. A method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 3, characterized in that, The volume ratio of oxygen to ozone in the mixed atmosphere is 9-8:1-2.

6. The method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 1, characterized in that, The specific preparation process of the substrate containing the layered WSe2 thin film in step three is as follows: The substrate containing the Ga2O3 thin film is fixed on the target holder, the WSe2 target is installed, and then it is placed in the pulsed laser deposition cavity. A vacuum operation is performed, and the temperature is raised to 390-410℃, with a vacuum degree of 5×10⁻⁶. -6 -5×10 -5 Pa, deposited for 8-12 min, and naturally cooled to room temperature to obtain a substrate containing a layered WSe2 thin film.

7. A method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 6, characterized in that, The parameters for pulsed laser deposition are: pulse frequency 1.8-2.2Hz, laser power 120-140mJ, and voltage 18-22kV.

8. A method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 1, characterized in that, The specific preparation process of the two-dimensional metallic material for the ultraviolet photodetector described in step four is as follows: A substrate containing a layered WSe2 thin film is fixed on the target holder and installed at a specific position within the cavity. Titanium particles and gold particles are placed in a double crucible, pre-evacuated to 0.8-1.2 Pa, and then evacuated to 3 × 10⁻⁶ Pa. -5 -8×10 -6 At a pressure of Pa for 8-12 min, a Ti layer is first deposited, the substrate is heated to 140-160℃, and the sputtering rate is 0.25-0.35 nm / s. Then, an Au layer is deposited, the substrate temperature is maintained, and the sputtering rate is 0.12-0.18 nm / s. The temperature is then raised to 190-210℃ in an argon atmosphere and held for 25-35 min. The temperature is then lowered to room temperature to obtain a two-dimensional metallic material for ultraviolet photodetectors.

9. A method for preparing a two-dimensional metallic material for an ultraviolet photodetector according to claim 8, characterized in that, The thickness of the Ti layer is 19-21 nm, and the thickness of the Au layer is 58-62 nm.

10. A two-dimensional metallic material for use in ultraviolet photodetectors, characterized in that, It is prepared by a method for preparing a two-dimensional metallic material for an ultraviolet photodetector as described in any one of claims 1-9.

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