Gallium oxide nanowire array type solar blind photoelectric detector and preparation method thereof

Abstract

The invention belongs to the technical field of photoelectric detection, and relates to a gallium oxide nanowire array type solar blind photoelectric detector and a preparation method thereof. Spreading liquid metal gallium on the surface of the substrate to form a liquid metal gallium layer on the surface of the substrate; performing vacuum evaporation on the surface of the liquid metal gallium layer to form a gold film layer to obtain a device precursor; and heating the device precursor to 400-1000 DEG C at a heating rate of 10-15 DEG C / min, and carrying out heat treatment for 1-2h to obtain the sandwich structure device. According to the method, the preparation mode of the array type gallium oxide nanowire is simplified, gallium metal left in the growth process is used as the electrode, the tedious and complex technological process needed in the previous device preparation process is improved, the ordered and regular gallium oxide nanowire array structure is prepared, and the photoelectric detection effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and relates to a gallium oxide nanowire array type solar-blind photoelectric detector and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Ultraviolet photodetectors have numerous civilian and military applications, such as biological / chemical analysis, flame sensing, covert air-to-air communications, missile tracking, and environmental monitoring. Because ozone and water vapor particles in the atmosphere strongly absorb deep ultraviolet light, solar radiation with wavelengths shorter than 280nm is virtually absent at the Earth's surface, hence the term "solar-blind region." Due to the low natural background in this solar-blind region, photodetectors operating in this spectral range offer advantages such as high signal-to-noise ratios and low false alarm rates. However, commercially used solar-blind detectors are typically bulky and fragile photomultiplier tubes (PMTs) that require large bias voltages, limiting their practical application.

[0004] Wide-bandgap semiconductors (WBGs) have attracted extensive research in the field of solar-blind detection due to their high radiation intensity, excellent thermal stability, and inherent solar-blind absorption properties. They offer a promising approach to addressing the current challenges of photomultiplier tubes (PMTs). Among WBGs, gallium oxide (GaO) boasts a bandgap of 4.9-5.3 eV, a high breakdown voltage, excellent optical transmittance, and physical and chemical stability, making it a promising candidate for solar-blind UV detectors. Currently, researchers have employed numerous methods to fabricate bulk, thin-film, and nanostructured materials. It is well known that the size and morphology of a material significantly influence its physical and chemical properties. The unique structure of nanowires provides a one-dimensional channel for carrier and photon transport and propagation while restricting their free motion in the other two dimensions. This structural feature enhances carrier transport efficiency and optical anisotropy. However, single nanowire devices suffer from relatively low current output and a small active area, raising practical challenges. Although nanowire arrays can be prepared through metal organic chemical vapor deposition, hydrothermal method, etching and other methods, there are often problems such as cumbersome operation procedures and poor repeatability. At the same time, the nanowire arrays prepared by existing methods all have disordered structures, which affects their photoelectric detection effect. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention provides a gallium oxide nanowire array-type solar-blind photodetector and its preparation method. This invention utilizes a simpler and more efficient method to prepare highly reproducible gallium oxide nanowire arrays, and utilizes a high-work-function metal alloy and residual gallium metal from the product growth process to construct a Schottky-type solar-blind photodetector. In addition to simplifying the preparation of the array-type gallium oxide nanowires, the use of residual gallium metal from the growth process as electrodes improves the cumbersome and complex process flow required for device fabrication. Furthermore, the invention produces an orderly and regular gallium oxide nanowire array structure, which is beneficial for improving photodetection performance.

[0006] In order to achieve the above object, the technical solution of the present invention is: In a first aspect, a method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Spreading liquid metal gallium on the surface of the substrate to form a liquid metal gallium layer on the surface of the substrate; Vacuum evaporating a gold film layer on the surface of the liquid metal gallium layer to obtain a device precursor; The device precursor is heated to 400-1000°C at a heating rate of 10-15°C / min and heat-treated for 1-2 hours to obtain a sandwich structure device; wherein, in the sandwich structure, the bottom layer is a substrate, the middle layer is a gallium metal layer, and the top layer is a gallium oxide nanowire array.

[0007] The method first applies non-toxic liquid gallium metal to the substrate surface, then vacuum-deposits a gold film. Gallium metal has a melting point of only 29.8°C and rapidly melts upon heating to form a liquid gallium layer. Gold, with a melting point of 1064°C, is solid at room temperature, but gallium and gold can form a low-melting-point eutectic alloy (at approximately 28°C). Therefore, liquid alloy droplets preferentially form at the gallium-gold interface of the vacuum-deposited gold film. When the liquid alloy droplets come into contact with oxygen, the gallium is oxidized to form gallium oxide (such as β-Ga2O3). Catalyzed by the liquid alloy droplets, the gallium oxide undergoes directional growth, ultimately forming a nanowire array. The surface atomic arrangement of the gold film creates a lattice match or low interfacial energy with the gallium oxide, guiding the nanowires to grow perpendicular to the substrate, forming an ordered array. In addition, the vacuum-evaporated gold film layer is more uniform, and the size of the gallium-gold alloy droplets formed is more uniform, making the diameter and spacing of the formed nanowires more uniform. Compared with metal gallium without gold film, metal gallium coated with gold film will form an ordered and regular array, thereby improving the photoelectric detection performance.

[0008] On the other hand, a gallium oxide nanowire array solar-blind photodetector is prepared by the above preparation method.

[0009] The beneficial effects of the present invention are: 1. The present invention vacuum-deposits a gold film layer on a metallic gallium layer. Gold and gallium form a eutectic alloy with a melting point of only approximately 28°C, providing a liquid phase environment at low temperatures, which can reduce energy consumption and improve the controllability of gallium oxide nanowire formation. It also has excellent chemical stability, is not easily oxidized, and can continuously maintain the activity of the liquid alloy catalytic center. Gold has a moderate adsorption / dissociation capacity for oxygen, which not only effectively promotes the reaction but also prevents over-adsorption that leads to saturation of active sites. It can also regulate the diffusion rate of gallium ions and control the growth rate and uniformity of gallium oxide nanowires. In addition, the surface energy of gold is well matched with gallium oxide, and there is a certain degree of lattice matching, which can reduce the interfacial energy barrier and promote the directional and orderly growth of gallium oxide nanowires.

[0010] 2. The preparation method of the present invention first spreads a metal gallium layer and then vacuum evaporates a gold film layer. While achieving efficient and convenient preparation, the product nanowire array has very good repeatability.

[0011] 3. The preparation method of the present invention can prepare oriented and ordered gallium oxide nanowire arrays. At the same time, it can directly provide the electrodes required for subsequent devices through the unique substrate-metal gallium-gallium oxide sandwich structure, simplifying the preparation steps of subsequent devices. Compared with traditional device preparation methods, the process is simpler.

[0012] 4. The solar-blind photodetector prepared by the present invention can work without an external power supply, and the device has an ultra-fast response speed to the solar-blind band, the response speed can reach millisecond level, and has a high photoelectric detection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 This is a SEM image of the gallium oxide nanowire array prepared in Example 1 of the present invention; Figure 2 This is a schematic structural diagram of a gallium oxide nanowire array photodetector prepared in Example 1 of the present invention; Figure 3 This is a dynamic light response diagram of the gallium oxide nanowire array photodetector obtained in Example 1 of the present invention; Figure 4 This is a dynamic light response diagram of the gallium oxide nanowire array photodetector obtained in Example 2 of the present invention; Figure 5 This is a SEM image of the gallium oxide product prepared in Comparative Example 1 of the present invention; Figure 6 This is a SEM image of the gallium oxide product prepared in Comparative Example 2 of the present invention; Figure 7 This is a SEM image of the gallium oxide product prepared in Comparative Example 4 of the present invention; Figure 8 The dynamic light response diagram of the photodetector prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0015] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0016] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0017] In view of the fact that the existing nanowire array preparation process is cumbersome and has poor repeatability, and the prepared nanowire arrays all have disordered structures, which affects the performance of photoelectric detection, the present invention proposes a gallium oxide nanowire array type solar-blind photodetector and its preparation method.

[0018] A typical embodiment of the present invention provides a method for preparing a gallium oxide nanowire array solar-blind photodetector, comprising the following steps: Spreading liquid metal gallium on the surface of the substrate to form a liquid metal gallium layer on the surface of the substrate; Vacuum evaporating a gold film layer on the surface of the liquid metal gallium layer to obtain a device precursor; The device precursor is heated to 400-1000°C at a heating rate of 10-15°C / min and heat-treated for 1-2 hours to obtain a sandwich structure device; wherein, in the sandwich structure, the bottom layer is a substrate, the middle layer is a gallium metal layer, and the top layer is a gallium oxide nanowire array.

[0019] The reason why the present invention vacuum evaporates a gold film layer on the surface of the liquid metal gallium layer is: 1. Excellent chemical stability. Gold hardly reacts with oxygen at room temperature and under heating conditions, and can always maintain the stability of the catalytic active center of the liquid alloy. Other metals (such as copper and iron) are easily oxidized to form an oxide shell, which hinders the oxidation reaction of gallium. 2. Formation of a low-melting-point eutectic alloy. Gold and gallium can form a low-melting-point eutectic alloy with a melting point of only about 28°C (about 20% gold and about 80% gallium), which is much lower than the melting points of gallium (29.8°C) and gold (1064°C). This ensures that the reaction can be carried out in a liquid phase environment at low temperatures, reducing energy consumption and improving controllability. 3. Surface energy and lattice matching promote growth: The surface energy of gold (about 1.52 J / m 2 ) matches well with β-Ga2O3, which can reduce the interfacial energy barrier. At the same time, the (111) crystal plane of gold and the (001) crystal plane of β-Ga2O3 have a certain degree of lattice matching (mismatch of about 15%), which can induce the preferential growth of gallium oxide along the

[001] direction, forming a highly ordered nanowire array. 4. The catalytic performance is moderate and controllable. Gold has a moderate ability to adsorb and dissociate oxygen molecules, which can effectively promote the oxidation reaction while avoiding the saturation of active sites due to excessive adsorption. In addition, the gold atoms in the liquid gold-gallium alloy can regulate the diffusion rate of gallium ions, thereby controlling the growth rate and diameter uniformity of the gallium oxide nanowires.

[0020] In some embodiments, an electrode is disposed above the gallium oxide nanowire array at the top of the sandwich device. The electrode is made of a metal with a higher work function at the Fermi level than gallium oxide. Specifically, the electrode is made of gold, nickel, or palladium. Gallium oxide is an n-type semiconductor. When it contacts a metal with a higher work function, it forms a Schottky contact; when it contacts a metal with a lower work function, it forms an ohmic contact. During the initial contact phase between the semiconductor and the metal, electrons flow from the semiconductor to the metal, as the Fermi level of the n-type semiconductor is generally higher than that of the metal. This electron transfer leads to the formation of a positive space charge region (depletion layer) at the semiconductor interface, while negative charge accumulates at the metal interface. In the absence of an applied voltage, when a Schottky heterojunction is used as a photodetector, the built-in electric field generates non-equilibrium electron-hole pairs, which separate due to light exposure. Electrons are driven into the semiconductor, while holes migrate toward the metal electrode. This carrier separation mechanism, driven by the built-in electric field of the Schottky heterojunction, enables the construction of a self-powered solar-blind UV detector. Specifically, the thickness of the electrode is 50 to 300 nm. Specifically, the electrode is deposited (or prepared) using electron beam deposition or thermal evaporation. Specifically, during the electrode deposition process, the electrode shape is controlled using a mask. The mask shape is not limited to square; it can also be circular, trapezoidal, triangular, or other shapes. More specifically, a mask is placed over the gallium oxide nanowire array at the top of the sandwich device, and then the electrode is deposited (or prepared) using electron beam deposition or thermal evaporation.

[0021] In some embodiments, the precursor material for the liquid gallium metal is a monolithic solid block of gallium with a purity of 99.9999%. Using a monolithic solid block of gallium as the precursor material for the liquid gallium metal can reduce pre-existing surface oxides, which is more effective than using micron-sized powders or granules. Specifically, the monolithic solid block of gallium is stored in an oxygen-free vacuum to prevent oxidation.

[0022] In some embodiments, the substrate is made of sapphire, silicon wafer, quartz, glass, or mica.

[0023] In some embodiments, liquid gallium metal is applied to the substrate after pretreatment. The pretreatment includes cleaning and / or oxygen plasma treatment. The cleaning process removes contaminants from the substrate surface. Specifically, the substrate is cleaned at least once with pure water, acetone, and alcohol, respectively. After cleaning, the substrate is dried. During oxygen plasma treatment, free radicals in the oxygen plasma impact the material surface, generating a large number of active free radicals. These free radicals combine with other free radicals in the substrate to implant oxygen-containing functional groups such as hydroxyl groups on the substrate surface, increasing the wettability of the substrate surface to gallium metal. Oxygen plasma treatment can also be used to pattern the substrate, thereby achieving patterned nanowire arrays for subsequent device design. Specifically, during oxygen plasma treatment, the oxygen flow rate is 0.5-1 L / min, and the treatment time is 2-3 minutes. Too short a treatment time can impair the substrate's wettability to gallium metal, while too long a treatment time can damage the substrate. Specifically, liquid gallium metal is applied to the substrate surface within one hour after oxygen plasma treatment. Avoid prolonged exposure of the oxygen plasma-treated surface to air for modification and aging.

[0024] In some embodiments, solid gallium metal is heated and melted to form liquid gallium metal. A substrate is preheated to a temperature not lower than the melting point of gallium metal, and the liquid gallium metal is then spread over the surface of the preheated substrate. Preheating the substrate prevents the gallium metal from solidifying. Specifically, the liquid gallium metal is evenly spread over the surface of the preheated substrate by pressing.

[0025] In some embodiments, 1-2 ml of liquid gallium is applied per square centimeter of substrate surface. Too little gallium will not remain after the reaction, which will affect the subsequent device preparation, and too little gallium will make it difficult to obtain a smooth surface.

[0026] In some embodiments, the thickness of the vacuum-evaporated gold film layer is 1-5 nm.

[0027] The optimized steps are as follows: Step 1: Sample preparation and pretreatment Preheat the hot plate to 120-150°C. In an oxygen-free glove box, place high-purity (99.9999%) bulk solid gallium metal in a container and heat it on the preheated hot plate until it is completely melted and liquid. Use a disposable dropper to draw up an appropriate amount of liquid gallium and dispense it into 10-50ml plastic bottles. Store the dispensed liquid gallium bottles in a vacuum container (or vacuum apparatus). Prepare two hot plates: one preheated to 120-150°C and the other to 35-50°C. Remove the plastic bottles containing the pre-dispensed bulk gallium metal from the vacuum container and place them on a hot plate at 120-150°C until the solid gallium in the bottles melts and liquidizes. Simultaneously, clean the substrate three times each with pure water, acetone, and alcohol, followed by drying with a nitrogen gun. The dried substrate is then treated with oxygen plasma using the following parameters: oxygen flow rate 0.5-1 L / min, treatment time 2-3 min.

[0028] Step 2: Gallium Oxide Nanowire Growth After the oxygen plasma treatment, the substrate is immediately placed on a preheated hot plate at 35-50°C. Within one hour, liquid gallium is added dropwise to the substrate using a disposable dropper at a ratio of 1-2 ml of liquid gallium per square centimeter of substrate, depending on the substrate area. A sapphire wafer that has not been treated with oxygen plasma is used to evenly spread the added liquid gallium onto the treated substrate surface by pressing. The substrate, with a uniform layer of liquid gallium, is placed in a vacuum evaporation apparatus and a 1-5 nm thick gold film is vacuum-deposited. The substrate, coated with liquid gallium and gold, is placed in a quartz boat. The quartz boat is placed in the quartz tube of a tube furnace. Under normal temperature and pressure, the tube furnace is heated at a rate of 10-15°C / min to a temperature of 400-1000°C and maintained at this temperature for 1-2 hours. After the temperature is maintained, the heating power is turned off and the tube furnace is allowed to cool naturally to room temperature. The final result is a sandwich structure consisting of a bottom substrate, an intermediate layer of metallic gallium (which is converted into gallium oxide after reaction), and a top layer of gallium oxide nanowire array.

[0029] Step 3: Electrode Preparation Place a pre-designed mask over the GaO nanowire array obtained in step 2. Use a metal with a work function higher than the Fermi level of GaO (such as gold (Au), nickel (Ni), or palladium (Pd)) to deposit a 50-300 nm thick metal electrode in the area defined by the mask using electron beam deposition or thermal evaporation. Remove the mask to create a Schottky-type GaO nanowire array solar-blind photodetector.

[0030] Another embodiment of the present invention provides a gallium oxide nanowire array solar-blind photodetector, which is prepared by the above-mentioned preparation method.

[0031] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0032] In the following examples, the gallium metal sample preparation process is as follows: Preheat a hot plate to 120-150°C. In an oxygen-free glove box, place high-purity (99.9999%) solid gallium metal in a container and heat it on the preheated hot plate until it is completely melted into a liquid state. Use a disposable dropper to draw an appropriate amount of liquid gallium and dispense it into 10-50ml plastic bottles. Place the dispensed liquid gallium bottles in a vacuum container (or vacuum device) for storage.

[0033] Example 1 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 120°C and the other to 35°C.

[0034] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 120°C until the solid gallium in the bottle melts into liquid.

[0035] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 0.5 L / min, treatment time 2 min.

[0036] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 35-50°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 1 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0037] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0038] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 1nm thick gold film layer.

[0039] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 500°C at a rate of 10°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 1 hour. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0040] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0041] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 50nm thick metal electrode is deposited in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0042] The picture of the gallium oxide nanowire array synthesized in this example is as follows Figure 1 As shown in FIG, it is shown that the present embodiment has prepared an ordered and regular gallium oxide nanowire array structure. The obtained gallium oxide nanowire array photodetector is as shown in FIG. Figure 2 The dynamic light response diagram of the detector is shown in Figure 3 As shown, the photodetector exhibits low dark current and an on / off ratio of 10 6 , fast response speed and good photoelectric performance.

[0043] Example 2 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 150°C and the other to 50°C.

[0044] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 150°C until the solid gallium in the bottle melts into liquid.

[0045] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 0.5 L / min, treatment time 2 min.

[0046] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 50°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 2 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0047] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0048] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 3nm thick gold film layer.

[0049] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 600°C at a rate of 10°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 1 hour. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0050] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0051] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 50nm thick metal electrode is deposited in the area defined by the mask by thermal evaporation. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0052] The dynamic light response diagram of the gallium oxide nanowire array photodetector obtained in this embodiment is shown in FIG. Figure 4 As shown, the photodetector also exhibits lower dark current, faster response speed and 10 6 The on / off ratio is excellent, and it has excellent photoelectric detection capabilities.

[0053] Example 3 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 130°C and the other to 40°C.

[0054] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 130°C until the solid gallium in the bottle melts into liquid.

[0055] c. Clean the substrate three times with pure water, acetone, and alcohol, respectively, then blow dry with a nitrogen gun. The dried substrate is treated with oxygen plasma with the following processing parameters: oxygen flow rate 1 L / min, treatment time 2 min.

[0056] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 40°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 1 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0057] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0058] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 2nm thick gold film layer.

[0059] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 500°C at a rate of 10°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 2 hours. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0060] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0061] b. Nickel (Ni), with a work function higher than the Fermi level of gallium oxide, is used to deposit a 100nm thick metal electrode in the area defined by a mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0062] Example 4 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 120°C and the other to 50°C.

[0063] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 120°C until the solid gallium in the bottle melts into liquid.

[0064] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 0.5 L / min, and processing time 3 min.

[0065] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 50°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 2 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0066] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0067] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 5nm thick gold film layer.

[0068] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 700°C at a rate of 15°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 1 hour. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0069] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0070] b. Nickel (Ni), with a work function higher than the Fermi level of gallium oxide, is used to deposit a 200nm thick metal electrode in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0071] Example 5 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 120°C and the other to 50°C.

[0072] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 120°C until the solid gallium in the bottle melts into liquid.

[0073] c. Clean the substrate three times with pure water, acetone, and alcohol, respectively, then blow dry with a nitrogen gun. The dried substrate is treated with oxygen plasma with the following processing parameters: oxygen flow rate 1 L / min, treatment time 2 min.

[0074] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 50°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 1 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0075] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0076] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 1nm thick gold film layer.

[0077] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 700°C at a rate of 15°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 2 hours. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0078] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0079] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 200nm thick metal electrode is deposited in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0080] Example 6 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 140°C and the other to 40°C.

[0081] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 140°C until the solid gallium in the bottle melts into liquid.

[0082] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 0.8 L / min, and processing time 2 min.

[0083] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 40°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 2 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0084] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0085] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 4nm thick gold film layer.

[0086] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. The quartz boat is then placed in the quartz tube of a tube furnace. Under normal temperature and pressure, the tube furnace is heated to 800°C at a rate of 15°C / min and held at this temperature for 2 hours. After the holding period, the heater is turned off and the tube furnace is allowed to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which is converted to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0087] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0088] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 300nm thick metal electrode is deposited in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0089] Example 7 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 150°C and the other to 35°C.

[0090] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 150°C until the solid gallium in the bottle melts into liquid.

[0091] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 1 L / min, and processing time 3 min.

[0092] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 35°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 2 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0093] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0094] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 1nm thick gold film layer.

[0095] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 1000°C at a rate of 15°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 1 hour. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0096] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0097] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 100nm thick metal electrode is deposited in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0098] Example 8 A method for preparing a gallium oxide nanowire array solar-blind photodetector comprises the following steps: Step 1: Preprocessing a. Prepare two hot plates: preheat one to 140°C and the other to 35°C.

[0099] b. Remove the plastic bottle containing the pre-packaged bulk gallium metal from the vacuum container and place it on a hot plate at 140°C until the solid gallium in the bottle melts into liquid.

[0100] c. The substrate was cleaned three times with pure water, acetone, and alcohol, respectively, and then dried with a nitrogen gun. The dried substrate was treated with oxygen plasma with the following processing parameters: oxygen flow rate 0.5 L / min, treatment time 2 min.

[0101] Step 2: Gallium Oxide Nanowire Growth a. After the oxygen plasma treatment, immediately place the substrate on a preheated hot plate at 35°C. Within 1 hour, use a disposable dropper to pipette liquid gallium onto the substrate at a ratio of 1 ml of liquid gallium per square centimeter of substrate, depending on the substrate area.

[0102] b. Take a sapphire wafer that has not been treated with oxygen plasma and spread the added liquid metal gallium evenly on the treated substrate surface by pressing.

[0103] c. Place the substrate with a uniform liquid metal gallium layer attached to the surface into a vacuum evaporation device and vacuum evaporate a 4nm thick gold film layer.

[0104] d. Place the substrate covered with liquid gallium and a gold film in a quartz boat. Place the quartz boat in the quartz tube of a tube furnace. Heat the tube furnace to 900°C at a rate of 10°C / min in an air atmosphere at room temperature and pressure, and hold the temperature for 2 hours. After the holding period, turn off the heating power and allow the tube furnace to cool naturally to room temperature. The result is a sandwich structure consisting of a bottom substrate, a middle layer of metal gallium (which converts to gallium oxide after the reaction), and a top layer of gallium oxide nanowire arrays.

[0105] Step 3: Electrode Preparation a. Cover the gallium oxide nanowire array obtained in step 2 with a mask.

[0106] b. Using gold (Au), whose work function is higher than the Fermi level of gallium oxide, a 100nm thick metal electrode is deposited in the area defined by the mask using electron beam deposition. Removing the mask yields a Schottky-type gallium oxide nanowire array solar-blind photodetector.

[0107] Comparative Example 1 This comparative example is the same as Example 1, except that in step 2d, the temperature of the tube furnace is increased to 200°C at a heating rate of 1°C / min and maintained at this temperature for 2 hours.

[0108] The obtained gallium oxide product is Figure 5 As shown, the gallium oxide nanowire array cannot be obtained because the heating rate is too slow and the temperature is too low.

[0109] Comparative Example 2 This comparative example is the same as Example 1, except that in step 2d, the temperature of the tube furnace is increased to 700° C. at a heating rate of 20° C. / min and maintained at this temperature for 20 min.

[0110] The obtained gallium oxide product is Figure 6 As shown, due to the short growth time and the fast heating time, only large-area granular products can be obtained in the end, and nanowire arrays cannot be obtained.

[0111] Comparative Example 3 This comparative example is the same as Example 1, except that in step 2a, liquid gallium was added dropwise to the substrate at a ratio of 0.5 ml of liquid gallium per square centimeter of substrate. Due to the relatively small amount of gallium on the substrate, it was completely oxidized during the oxidation process, and the desired structure could not be obtained.

[0112] Comparative Example 4 This comparative example is the same as Example 1, except that: step c in step 2 is omitted, that is, the gold film layer is not vacuum evaporated on the liquid gallium.

[0113] The obtained gallium oxide product is Figure 7 As shown, the gallium oxide nanowire array prepared in this comparative example is a disordered structure with low regularity. This proves that the surface oxidation rate of gallium is difficult to uniformly control during the oxidation process, and the array regularity is usually lower than that of catalytic growth.

[0114] In addition, the on / off ratio of the device prepared in this comparative example is 10 3 , its photoelectric performance shows a poor photoelectric detection effect compared with array-type gallium oxide, such as Figure 8 This is because non-arrayed nanowires, due to their disordered stacking, are prone to forming light reflection "dead spots" (such as random blocking between nanowires or excessive gaps), causing some light to escape without being absorbed. Arrayed nanowires, on the other hand, (e.g., arranged perpendicular to the substrate), can regulate light scattering and interference through a periodic structure, causing light to reflect multiple times within the array (similar to the "light trap" effect), extending the interaction time between light and nanowires, increasing the probability of absorption, and resulting in a stronger photocurrent.

[0115] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a gallium oxide nanowire array solar-blind photodetector, characterized in that: The steps include: Spreading liquid metal gallium on the surface of the substrate to form a liquid metal gallium layer on the surface of the substrate; Vacuum evaporating a gold film layer on the surface of the liquid metal gallium layer to obtain a device precursor; The device precursor is heated to 400-1000°C at a heating rate of 10-15°C / min and heat-treated for 1-2 hours to obtain a sandwich structure device; wherein, in the sandwich structure, the bottom layer is a substrate, the middle layer is a gallium metal layer, and the top layer is a gallium oxide nanowire array.

2. The preparation method according to claim 1, wherein An electrode is arranged on the upper part of the gallium oxide nanowire array on the top of the sandwich structure device. The material of the electrode is a metal having a work function at the Fermi level higher than that of gallium oxide.

3. The preparation method according to claim 1, wherein the liquid The precursor material of metallic gallium is a solid block of gallium with a purity of 99.9999%.

4. The preparation method according to claim 1, wherein The substrate is made of sapphire, silicon wafer, quartz, glass or mica.

5. The preparation method according to claim 1, wherein The liquid metal gallium is spread after the substrate is pretreated, wherein the pretreatment includes cleaning and / or oxygen plasma treatment.

6. The preparation method according to claim 5, characterized in that: Liquid metal gallium is spread on the substrate surface within 1 hour after oxygen plasma treatment.

7. The preparation method according to claim 1, wherein: Solid metal gallium is heated and melted to form liquid metal gallium, and the substrate is preheated to a temperature not lower than the melting point of the metal gallium, and then the liquid metal gallium is spread on the surface of the preheated substrate.

8. The preparation method according to claim 1, wherein Spread 1~2ml of liquid metal gallium per square centimeter of substrate surface.

9. The preparation method according to claim 1, wherein: The thickness of the vacuum-deposited gold film is 1~5nm.

10. A gallium oxide nanowire array solar-blind photodetector, characterized in that: The method is prepared according to any one of claims 1 to 9.

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