Gallium oxide gas sensor and its preparation method and application

Abstract

The present invention discloses a gallium oxide gas sensor and its preparation method and application. The gallium oxide gas sensor comprises: a gallium oxide nanocolumn array and a two-dimensional conductive material, wherein the gallium oxide nanocolumn array comprises a plurality of gallium oxide nanocolumns distributed at intervals, the gallium oxide nanocolumns are arranged in a standing position, the two-dimensional conductive material continuously covers the gallium oxide nanocolumn array, and the two-dimensional conductive material cooperates with the gallium oxide nanocolumn array to form a heterojunction, and the gallium oxide nanocolumn array and the two-dimensional conductive material are also electrically connected to a first electrode and a second electrode, respectively. The gallium oxide gas sensor provided by the present invention comprises a plurality of gallium oxide nanocolumns perpendicular to the surface of a conductive substrate, has a more efficient material utilization rate, and can fully contact and react with more gas molecules, which is beneficial to the improvement of the gas sensing performance of the device and its miniaturization process.

Description

Technical Field

[0001] The invention relates to a gas sensor, in particular to a gallium oxide gas sensor and a preparation method and application thereof, belonging to the fields of electronic information and technology and semiconductor technology. Background Art

[0002] With the rapid development of modern industry, air pollution caused by industrial waste gas, automobile exhaust, etc. has attracted more and more attention; especially gas leakage in industrial production, which often easily causes major safety accidents. Therefore, it is very necessary to effectively detect various toxic and harmful gases to achieve early warning and eliminate safety hazards. Semiconductor metal oxides play an important role in the field of gas detection due to their advantages such as high sensitivity, low operating temperature, small size and low price. At present, commonly used gas-sensitive materials include NiO, SnO2, WO3, etc. These materials include various forms such as nanoparticles, nanofilms, nanotubes and nanowires. Compared with traditional bulk or thin film sensors, nanosensors have the characteristics of large specific surface area, high surface activity, strong adsorption capacity, high sensitivity and good conductive structure.

[0003] Therefore, in recent years, nano gas sensors have received more and more attention as a new generation of gas sensors. Among them, nano arrays have gradually become an excellent structure for gas sensor electronic devices due to their unique active surface and large specific surface area. Because of their large specific surface area, nano arrays can contact more gas molecules in the air than bulk materials under the same volume, thus having higher sensitivity and shorter response time, and can quickly detect gas changes in the environment.

[0004] On the other hand, metal oxide nanowire materials are also ideal primitives for constructing nanosensor devices. They can not only serve as reliable nanoscale connecting wires, but also have device functions. Through doping, doped nanowires and their heterojunction structures can be easily obtained. Therefore, gas detectors based on nanowires have also developed rapidly in recent years. Metal oxide semiconductor gas sensors have become the most widely used gas sensors due to their simple structure, low cost, and excellent comprehensive performance. The sensitive materials are mostly bulk, nanoparticles or thin films. Common sintered (resistance) gas sensors mostly use a side-heated structure, which is large in size and needs to be heated to a high temperature of several hundred degrees to show good sensitive characteristics, so the power consumption is high. However, whether it is a resistance type or a junction type gas sensor, it is still unsatisfactory in terms of volume, sensitivity, stability, response speed, gas selectivity and durability. However, for existing nanowire gas sensors, most of them are difficult to prepare and difficult to achieve industrialization.

[0005] like Figure 1As shown, a conventional resistive gas sensor based on a block or thin film uses a single metal oxide as a sensitive material. Due to the adsorption and desorption reaction of the gas on the surface of the material, the carrier concentration changes, and this reaction can be intensified by heating. At this time, by detecting the change in the resistance of the material, the amount of gas involved in the reaction can be calculated, which can be used to characterize the gas concentration in the environment. Although this device has a simple structure and is easy to prepare, its electrical properties come from a single metal oxide material and are dominated by the in-plane conduction mechanism, so it has the disadvantages of large size, high power consumption, inaccurate temperature control, low sensitivity, poor stability, and weak response-recovery ability.

[0006] like Figure 2 As shown in FIG. 1 , a junction-type gas sensor based on a pn junction is used. Since the junction-type sensor utilizes the change in the electrical carrier transport characteristics of the semiconductor junction region, its sensitivity to gas molecule detection is often greater than that of a resistance-type sensor. Figure 2 Taking the pn junction gas sensor as an example, the existence of the pn junction can show novel electrical properties, and combining two or more semiconductors to form a heterojunction interface can enhance the performance of the gas sensor. However, this structure is usually based on bulk materials or thin films, with a small contact surface and a large device volume. It also faces problems such as low sensitivity, slow response time, and limited operating temperature. Summary of the invention

[0007] The main purpose of the present invention is to provide a gallium oxide gas sensor and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0008] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0009] An embodiment of the present invention provides a gallium oxide gas sensor, which includes a gallium oxide nanocolumn array and a two-dimensional conductive material. The gallium oxide nanocolumn array includes a plurality of gallium oxide nanocolumns distributed at intervals, the gallium oxide nanocolumns are arranged upright, the two-dimensional conductive material continuously covers the gallium oxide nanocolumn array, and the two-dimensional conductive material cooperates with the gallium oxide nanocolumn array to form a heterojunction, and the gallium oxide nanocolumn array and the two-dimensional conductive material are also electrically connected to a first electrode and a second electrode, respectively.

[0010] In some more specific embodiments, the gallium oxide nanorod array is disposed on a conductive substrate, and the gallium oxide nanorod array and the first electrode are electrically coupled to the conductive substrate, and an insulating passivation layer is disposed between the two-dimensional conductive material and the conductive substrate.

[0011] Furthermore, the diameter of the gallium oxide nanorod is 10-1000 nm.

[0012] Preferably, the length of the gallium oxide nanorods is 10-1000 nm.

[0013] Preferably, the distance between two adjacent gallium oxide nanorods is 10-1000 nm.

[0014] Preferably, the gallium oxide nanorod is a cylindrical, truncated cone, conical or pyramidal structure, but is not limited thereto.

[0015] Preferably, the gallium oxide nanorods are β-Ga2O3 nanorods.

[0016] Furthermore, the gallium oxide nanocolumn array formed by the plurality of gallium oxide nanocolumns is evenly and orderly distributed, rather than randomly and staggeredly stacked; the distribution form of the gallium oxide nanocolumn array can be as follows: Figure 5 As shown in, of course, Figure 5 Only one uniform and orderly distribution form of the plurality of gallium oxide nanorods is shown, and the plurality of gallium oxide nanorods may also be distributed in other uniform and orderly forms, which are not specifically limited here.

[0017] Furthermore, the two-dimensional conductive material includes any one of graphene and molybdenum disulfide, but is not limited thereto.

[0018] Preferably, the thickness of the two-dimensional conductive material is 1 nm-1 μm.

[0019] Furthermore, the gallium oxide nanorod array is n-type doped, and the two-dimensional conductive material is p-type doped.

[0020] Furthermore, the two-dimensional conductive material forms a van der Waals heterojunction with the gallium oxide nanorod array.

[0021] Furthermore, the n-type doping concentration of the gallium oxide nanorod array is 1×10 15 -10 21 cm -3 .

[0022] Furthermore, the p-type doping concentration of the two-dimensional conductive material is 1×10 15 -10 21 cm -3 .

[0023] Furthermore, the plurality of gallium oxide nanorods are arranged upright (which can be understood as being arranged vertically or perpendicularly).

[0024] Preferably, the gallium oxide nanorods are vertically arranged on the conductive substrate.

[0025] Furthermore, the insulating passivation layer is integrally provided with the conductive substrate.

[0026] Preferably, the insulating passivation layer is formed by passivating a local area of ​​the conductive substrate.

[0027] Preferably, the two-dimensional conductive material is in contact with the insulating passivation layer, and the second electrode is electrically coupled to the two-dimensional conductive material.

[0028] Furthermore, the material of the conductive substrate includes Si or GaN, but is not limited thereto.

[0029] Preferably, the thickness of the conductive substrate is 1 μm-1 mm.

[0030] Preferably, the thickness of the insulating passivation layer is 1 nm-1 um.

[0031] Preferably, the first electrode is a cathode, and the second electrode is an anode.

[0032] The embodiment of the present invention further provides a method for preparing the gallium oxide gas sensor, which comprises:

[0033] Growing a gallium oxide nanorod array on a conductive substrate;

[0034] Performing a passivation treatment on a partial area of ​​the conductive substrate, thereby forming an insulating passivation layer on the conductive substrate;

[0035] Covering the gallium oxide nanorod array with a continuous two-dimensional conductive material, and contacting the two-dimensional conductive material with the insulating passivation layer;

[0036] A first electrode and a second electrode are respectively manufactured on the conductive substrate and the two-dimensional conductive material.

[0037] Specifically, the preparation method includes: performing a passivation treatment on a partial area of ​​the conductive substrate by at least ion implantation.

[0038] The embodiment of the present invention also provides a gas detection method, which includes:

[0039] The gas to be detected is brought into contact with the gallium oxide gas sensor, and qualitative and / or quantitative detection of the gas to be detected is achieved based on the electrical signal output by the gallium oxide gas sensor;

[0040] The gas to be detected includes but is not limited to CO, CH4 or O2.

[0041] Compared with the prior art, the advantages of the present invention include:

[0042] 1) A gallium oxide gas sensor provided by an embodiment of the present invention, wherein the gallium oxide nanorod array comprises a plurality of gallium oxide nanorods perpendicular to the surface of a conductive substrate. Compared with conventional flat nanowires, the stacking of nanostructures is reduced, thereby obtaining a more efficient material utilization rate, and thus being able to fully contact and react with more gas molecules, which is beneficial to the improvement of the gas sensing performance of the device and its miniaturization process;

[0043] 2) A gallium oxide gas sensor provided in an embodiment of the present invention forms a van der Waals heterojunction by selecting a suitable two-dimensional conductive material and a gallium oxide nanorod array. On the one hand, the van der Waals heterojunction overcomes the disadvantages of interface stress, defects, Fermi level pinning, etc., and can obtain excellent electrical properties; on the other hand, relying on the influence of trace gas molecules on the heterojunction barrier and the synergistic effect between different materials, a gas sensor with fast response, high sensitivity and good selectivity can be realized;

[0044] 3) A gallium oxide gas sensor provided in an embodiment of the present invention forms a pn junction by regulating the n-type doping concentration of gallium oxide nanorods and the p-type doping concentration of two-dimensional conductive materials. Due to the adsorption and desorption of gas molecules, the energy band near the pn junction interface is bent, resulting in significant changes in electrical characteristics, thereby greatly improving the sensitivity of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the structure of a conventional resistive gas sensor based on a block material or a thin film in the prior art;

[0046] Figure 2 It is a schematic diagram of the structure of a junction-type gas sensor based on a pn junction in the prior art;

[0047] Figure 3 It is a structural schematic diagram of a gallium oxide gas sensor in a typical implementation case of the present invention;

[0048] Figure 4 It is a schematic diagram of the manufacturing process of a gallium oxide gas sensor in a typical implementation case of the present invention;

[0049] Figure 5 is a SEM image of an ordered gallium oxide nanorod array grown in a typical implementation case of the present invention. DETAILED DESCRIPTION

[0050] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0051] Gallium oxide is a direct broadband oxide semiconductor material with an energy band gap of Eg = 4.9eV and a melting point of 1725°C. Its excellent electrical properties and luminescence properties have long been the focus of attention. At high temperatures, unintentionally doped gallium oxide exhibits n-type conductivity, and its conductivity varies with changes in the ambient atmosphere and concentration. In addition, gallium oxide has the advantages of being low in price, non-toxic, easy to etch, and having stable physical and chemical properties. Studies have found that gallium oxide has obvious gas-sensitive properties for gases such as CO, CH4, and O2. Compared with traditional thin-film gas sensors, it has shown greater potential in the preparation of highly sensitive gas-sensitive sensors.

[0052] With the development of miniaturization of sensor devices, gas sensors based on nanomaterials can fully contact with more gas molecules due to their larger specific surface area, thus conforming to the miniaturization of devices and achieving higher sensitivity and faster response-recovery time.

[0053] A gallium oxide gas sensor provided by an embodiment of the present invention has the advantage of a large specific surface area compared to traditional bulk materials or thin film materials, so that the gas molecules to be detected in the environment can be effectively adsorbed onto the surface of the gallium oxide material, thereby increasing the reaction intensity and making it easier to realize a highly sensitive gas detector; and, in a gallium oxide gas sensor provided by an embodiment of the present invention, the gallium oxide nanocolumn array is perpendicular to the surface of the conductive substrate, and the diameter, density and vertical ratio of the nanocolumns can be adjusted. Compared with conventional flat nanowire structures, it has a more efficient material utilization rate and is more conducive to realizing a highly integrated, miniaturized, and low-power gas sensor.

[0054] A gallium oxide gas sensor provided by an embodiment of the present invention directly grows a gallium oxide nanorod array on a conductive substrate. Compared with an array formed by an etching process, the present invention avoids the introduction of impurity ions, has less damage, and has a simpler manufacturing process, and is therefore more beneficial to improving the gas sensing performance of the device. In addition, the present invention combines the excellent properties of the pn junction between the gallium oxide nanorod array and the two-dimensional conductive material. Due to the adsorption and desorption of gas molecules, the energy band near the pn junction interface is bent, resulting in a significant change in electrical properties, thereby greatly improving the sensitivity of the device.

[0055] A gallium oxide gas sensor provided by an embodiment of the present invention selects a suitable two-dimensional conductive material and a gallium oxide nanorod array to form a heterojunction, and the synergistic effect of different sensitive materials can be combined to improve the selectivity and sensitivity of the sensor. In addition, the electron-hole pairs in the heterojunction recombine rapidly, and the heterojunction potential barrier can change significantly under the influence of a trace amount of gas molecules, thereby realizing a fast-response, high-sensitivity gas sensor; wherein, the two-dimensional conductive material in the gallium oxide gas sensor provided by an embodiment of the present invention can adopt two-dimensional materials such as graphene, and graphene can form a van der Waals heterojunction with gallium oxide. Since the shortcomings of interface stress, defects, and Fermi level pinning are overcome, the performance of the gas sensor provided by the embodiment of the present invention will be greatly improved.

[0056] In the manufacturing process of a gallium oxide gas sensor provided by an embodiment of the present invention, the high mechanical strength and good conductivity of two-dimensional conductive materials such as graphene are utilized to deposit anode metal on top of the two-dimensional conductive material, thereby preventing the gallium oxide nanocolumn array from being destroyed; and, by adjusting the n-type doping concentration of the gallium oxide nanocolumns, the energy level structure of the gallium oxide nanocolumns can be regulated, thereby adjusting the junction width and gas sensing performance of the gallium oxide nanocolumn array gas sensor, and further improving the sensitivity of the gallium oxide gas sensor and reducing power consumption; as known to those skilled in the art, the physical properties of the nanowires of the gallium oxide material are basically the same as those of the thin film material, both of which are wide bandgap semiconductor materials and are only sensitive to certain gases; and by means of n-type doping, the conductive properties of the gallium oxide material can be adjusted, thereby adjusting the gas sensing properties of the device.

[0057] See also Figure 3 A gallium oxide gas sensor provided by an embodiment of the present invention includes: a gallium oxide nanocolumn array and a two-dimensional conductive material, wherein the gallium oxide nanocolumn array includes a plurality of gallium oxide nanocolumns distributed at intervals, the gallium oxide nanocolumns are arranged upright, the two-dimensional conductive material continuously covers the gallium oxide nanocolumn array, and the two-dimensional conductive material cooperates with the gallium oxide nanocolumn array to form a heterojunction, and the gallium oxide nanocolumn array and the two-dimensional conductive material are also electrically connected to a cathode and an anode, respectively.

[0058] Specifically, the gallium oxide nanocolumn array and the cathode are both arranged on a conductive substrate, and the gallium oxide nanocolumn array and the cathode are both electrically combined with the conductive substrate, and an insulating passivation layer (i.e., the passivation layer in the figure, the same below) is arranged between the two-dimensional conductive material and the conductive substrate; preferably, the insulating passivation layer and the conductive substrate are integrally arranged, the insulating passivation layer is formed by passivation treatment of a local area of ​​the conductive substrate, a local area of ​​the two-dimensional conductive material is in contact with the insulating passivation layer, and the anode is electrically combined with the two-dimensional conductive material; wherein the material of the conductive substrate includes but is not limited to Si or GaN, the thickness of the conductive substrate is 1μm-1mm, and the thickness of the insulating passivation layer is 1nm-1μm.

[0059] Specifically, the plurality of gallium oxide nanorods are vertically arranged on a conductive substrate, and the gallium oxide nanorods are n-type doped, and the n-type doping concentration of the gallium oxide nanorods is 1×10 15 -10 21 cm -3 The two-dimensional conductive material is p-type doped, and the p-type doping concentration of the two-dimensional conductive material is 1×10 15 -10 21 cm -3 The two-dimensional conductive material forms a van der Waals pn heterojunction with the gallium oxide nanorod array; preferably, the cathode and the anode can both be metal electrodes, and their specific materials can be metals known to those skilled in the art.

[0060] Specifically, the diameter of a single gallium oxide nanocolumn is 10-1000nm, the length is 10-1000nm, the spacing between two adjacent gallium oxide nanocolumns is 10-1000nm, and preferably, the gallium oxide nanocolumn is a columnar structure such as a cylindrical, truncated cone, conical or pyramidal shape, but not limited thereto; preferably, the gallium oxide nanocolumn can be a β-Ga2O3 nanocolumn.

[0061] Specifically, the plurality of gallium oxide nanorods are evenly and orderly distributed.

[0062] Specifically, the two-dimensional conductive material includes any one of graphene and molybdenum disulfide, and the thickness of the two-dimensional conductive material is 1 nm-1 μm.

[0063] The invention adopts a simple gallium oxide nano-column growth process to prepare a gas sensor with an ordered vertical gallium oxide nano-column array.

[0064] See also Figure 4 In a typical embodiment of the present invention, a method for manufacturing a gallium oxide thin film gas sensor may include the following steps:

[0065] 1) A plurality of standing gallium oxide nanorods are directly grown on a conductive substrate using epitaxial techniques such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE), and the plurality of gallium oxide nanorods are n-doped, with an n-type doping concentration of 1×10 15 -10 21 cm -3 , thereby forming a vertical gallium oxide nanocolumn array;

[0066] 2) performing a passivation treatment on a part of the conductive substrate (i.e., the area below the anode) by ion implantation or the like, so that an insulating passivation layer is formed locally on the conductive substrate;

[0067] 3) Providing a two-dimensional conductive material (thickness of 1 nm-1 μm), and performing p-type doping on the two-dimensional conductive material, controlling the concentration of the p-type doping to be 1×10 15 -10 21 cm -3 ; Then, the two-dimensional conductive material is transferred onto the gallium oxide nanorod array, and part of the two-dimensional conductive material is in contact with the passivation layer of the substrate, and the two-dimensional conductive material forms a van der Waals heterojunction with the gallium oxide nanorod array;

[0068] The preparation method and transfer process of the two-dimensional conductive material may include the following steps:

[0069] First, a layer of two-dimensional conductive material is formed on a copper foil substrate, and a layer of polymethyl methacrylate (PMMA) solution is spin-coated on the surface of the two-dimensional conductive material, and the PMMA / two-dimensional conductive material / copper foil is placed on a constant temperature heating table for heating (the heating temperature can be adjusted according to the common knowledge of those skilled in the art and is not specifically limited here), so that the PMMA solution undergoes a glass transition and solidifies;

[0070] Then, PMMA / two-dimensional conductive material / copper foil was suspended and placed in a 1 mol / L FeCl3 solution to corrode the copper foil substrate. After the copper foil substrate was completely corroded, PMMA / two-dimensional conductive material was transferred to the gallium oxide nanorod array, and the gallium oxide nanorod array / two-dimensional conductive material / PMMA was placed in an acetone solution and heated in a 40°C water bath for 30 min to remove PMMA. Finally, the laminated structure was cleaned with anhydrous ethanol and deionized water respectively and dried naturally at room temperature.

[0071] 4) Using metal deposition techniques such as electron beam evaporation or sputtering, a cathode metal electrode is made on a conductive substrate, and an anode metal electrode is made on a two-dimensional conductive material, thereby forming the gallium oxide thin film gas sensor; the gallium oxide thin film gas sensor can detect certain gases (such as CO, CH4, O2, etc.) in the environment under certain bias voltage conditions (such as 5V).

[0072] The technical solution of the present invention will be described in more detail below in conjunction with the accompanying drawings and specific implementation cases. It should be understood that, unless otherwise specified, the raw materials and equipment used in the following embodiments can be obtained through market purchase and other channels, and the processes such as inductively coupled plasma chemical vapor deposition, photolithography, reactive ion etching, MOCVD, H ion implantation, etc. used therein can be implemented according to methods known in the art.

[0073] Embodiment 1:

[0074] A method for manufacturing a gallium oxide thin film gas sensor may include the following steps:

[0075] 1) Making a mask with an ordered nanopore array, specifically comprising: depositing a 50 nm thick SiO2 mask layer on a GaN template (including a sapphire substrate and a GaN layer deposited on the substrate, referred to as GaN / sapphire substrate) by inductively coupled plasma chemical vapor deposition at room temperature, and spin-coating a 400 nm thick polymethyl methacrylate (PMMA) photoresist on the SiO2 mask layer, followed by electron beam exposure, and then selectively etching the SiO2 mask layer by reactive ion etching to expose the GaN template from the nanopores on the SiO2 mask layer for the nucleation growth of nanocolumns; then performing a debonding treatment with acetone and isopropanol, thereby forming a SiO2 mask with an ordered nanopore array (i.e., a patterned SiO2 mask) on the GaN template; wherein, by regulating the process conditions of the reactive ion etching method, the aperture and period of the nanopores on the patterned SiO2 mask can be adjusted;

[0076] 2) using MOCVD or other epitaxial technologies, respectively using high-purity (purity ≥ 99.999%) N2O or O2, triethylgallium (TEGa) as an oxygen source and a gallium source, firstly pre-depositing a metal Ga catalyst on the surface of the GaN / sapphire substrate with a patterned SiO2 mask obtained in step (1) at 450° C. for 5 minutes, and the deposition flow rate of the metal Ga catalyst is 200 sccm; after the metal Ga catalyst is deposited, annealing is performed at 650° C. for 5 minutes. The process is carried out for 10 minutes, wherein the diameter and density of the gallium oxide nanopillars can be controlled by adjusting the process conditions in the pre-deposition and annealing steps; then the temperature is lowered, and an oxygen source and a gallium source are introduced into the reaction chamber again, and the flow rates of the oxygen source and the gallium source are controlled to be 700sccm and 200sccm respectively, and the growth is carried out at 500°C for 10 minutes, thereby obtaining a plurality of gallium oxide nanopillars perpendicular to the substrate and distributed in an orderly manner, and then obtaining a gallium oxide nanopillar array, wherein the gallium oxide nanopillar has a diameter of 200nm and a height of 1000nm. Figure 5 The SEM image of an orderly distributed gallium oxide nanorod array prepared in this embodiment is shown;

[0077] 3) performing a passivation treatment on a portion of the GaN / sapphire substrate having the gallium oxide nanorod array after the treatment in step (2) by means of H ion implantation to form a high-resistance insulating layer;

[0078] 4) using a van der Waals force adhesion method to transfer the p-type graphene grown on the copper foil to the surface of the aforementioned gallium oxide nanorod array (the preparation and transfer process of the p-type graphene can refer to the preparation and transfer of the aforementioned two-dimensional conductive material), and the p-type graphene and the gallium oxide nanorod array are combined to form a van der Waals heterojunction;

[0079] 5) Using electron beam evaporation technology, Ti / Au is deposited on the p-type graphene as a metal anode, and Ti / A1 / Ni / Au is deposited on the surface of the substrate as a metal cathode, thereby completing the preparation of the gallium oxide gas sensor.

[0080] It should be noted that the gallium oxide nanocolumns are formed in the area where the metal Ga catalyst is deposited. The purpose of the patterned SiO2 mask is to form the metal Ga catalyst in a specified distribution pattern in a specified specific area, thereby growing the gallium oxide nanocolumns. The metal Ga catalyst will not be deposited in the area covered by the patterned SiO2 mask, and thus the gallium oxide nanocolumns will not be formed. Of course, it is also possible to not set a mask and directly deposit the metal Ga catalyst in the specified area on the substrate surface. After annealing, a uniformly distributed metal Ga catalyst can be formed, and it can also be used to form gallium oxide nanocolumns.

[0081] The embodiment of the present invention adopts epitaxial growth processes such as MOCVD to prepare vertical gallium oxide nanowire arrays on a large scale, and combines semiconductor processes to further manufacture gallium oxide gas sensors. The preparation method provided by the embodiment of the present invention has a simple process, and the obtained device has excellent performance and can be applied on a large scale.

[0082] The gallium oxide gas sensor provided by the embodiment of the present invention has a nanocolumn array that can increase the surface area of ​​the device, and combined with the excellent physical properties of two-dimensional conductive materials, can further improve the range and sensitivity of the gas detector.

[0083] An embodiment of the present invention provides a gallium oxide gas sensor, wherein the gallium oxide nanorod array includes a plurality of gallium oxide nanorods perpendicular to the surface of a conductive substrate. Compared with conventional flat nanowires, the stacking of nanostructures is reduced, thereby obtaining a more efficient material utilization rate, and thus being able to fully contact and react with more gas molecules, which is beneficial to the improvement of the gas sensing performance of the device and its miniaturization process;

[0084] A gallium oxide gas sensor provided by an embodiment of the present invention adopts a mask method or a non-mask method, and by controlling the deposition time and annealing process in the epitaxial process, an ordered (that is, it can be understood as uniform arrangement) gallium oxide nanocolumn array can be prepared. The diameter, vertical ratio and density of the gallium oxide nanocolumns can be adjusted to achieve more efficient material utilization and greatly improve the gas sensing performance of the device.

[0085] A gallium oxide gas sensor provided by an embodiment of the present invention forms a van der Waals heterojunction by selecting a suitable two-dimensional conductive material and a gallium oxide nanorod array. On the one hand, the van der Waals heterojunction overcomes the disadvantages of interface stress, defects, Fermi level pinning, etc., and can obtain excellent electrical properties; on the other hand, relying on the influence of trace gas molecules on the heterojunction barrier and the synergistic effect between different materials, a gas sensor with fast response, high sensitivity and good selectivity can be realized;

[0086] A gallium oxide gas sensor provided by an embodiment of the present invention forms a pn junction by regulating the n-type doping concentration of gallium oxide nanorods and the p-type doping concentration of two-dimensional conductive materials. Due to the adsorption and desorption of gas molecules, the energy band near the pn junction interface is bent, resulting in significant changes in electrical characteristics, thereby greatly improving the sensitivity of the device.

[0087] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A gallium oxide gas sensor, characterized in that The invention comprises a gallium oxide nanocolumn array and a two-dimensional conductive material, wherein the gallium oxide nanocolumn array comprises a plurality of gallium oxide nanocolumns distributed at intervals, the gallium oxide nanocolumns are arranged in a standing position, the diameter of the gallium oxide nanocolumns is 10-1000 nm, the length of the gallium oxide nanocolumns is 10-1000 nm, the spacing between two adjacent gallium oxide nanocolumns is 10-1000 nm, the gallium oxide nanocolumns are β-Ga2O3 nanocolumns, the two-dimensional conductive material continuously covers the gallium oxide nanocolumn array, the thickness of the two-dimensional conductive material is 1 nm-1 μm, the gallium oxide nanocolumn array is n-type doped, and the n-type doping concentration of the gallium oxide nanocolumn array is 1× 10 15 -10 21 cm -3 , the two-dimensional conductive material is p-type doped, and the p-type doping concentration of the two-dimensional conductive material is 1×10 15 -10 21 cm -3 The two-dimensional conductive material forms a van der Waals heterojunction with the gallium oxide nanocolumn array. The gallium oxide nanocolumn array and the two-dimensional conductive material are also electrically connected to the first electrode and the second electrode respectively. The two-dimensional conductive material includes any one of graphene and molybdenum disulfide.

2. The gallium oxide gas sensor according to claim 1, characterized in that: The gallium oxide nanorod array is arranged on a conductive substrate, and the gallium oxide nanorod array and the first electrode are electrically combined with the conductive substrate, and an insulating passivation layer is arranged between the two-dimensional conductive material and the conductive substrate.

3. The gallium oxide gas sensor according to claim 1, characterized in that: The gallium oxide nanorod is in a cylindrical, truncated cone, conical or pyramidal structure.

4. The gallium oxide gas sensor according to claim 1, characterized in that: The plurality of gallium oxide nanorods are evenly and orderly distributed.

5. The gallium oxide gas sensor according to claim 2, characterized in that: The gallium oxide nanorods are vertically arranged on the conductive substrate.

6. The gallium oxide gas sensor according to claim 2, characterized in that: The insulating passivation layer is integrally arranged with the conductive substrate.

7. The gallium oxide gas sensor according to claim 6, characterized in that: The insulating passivation layer is formed by passivating a local area of ​​the conductive substrate.

8. The gallium oxide gas sensor according to claim 2, characterized in that: The two-dimensional conductive material is in contact with the insulating passivation layer, and the second electrode is electrically combined with the two-dimensional conductive material.

9. The gallium oxide gas sensor according to claim 2 or 6, characterized in that: The conductive substrate is made of Si or GaN.

10. The gallium oxide gas sensor according to claim 2 or 6, characterized in that: The thickness of the conductive substrate is 1 μm-1 mm.

11. The gallium oxide gas sensor according to claim 2 or 6, characterized in that: The thickness of the insulating passivation layer is 1 nm-1 μm.

12. The gallium oxide gas sensor according to claim 2 or 6, characterized in that: The first electrode is a cathode, and the second electrode is an anode.

13. The method for preparing the gallium oxide gas sensor according to any one of claims 1 to 12, characterized in that include: Growing a gallium oxide nanorod array on a conductive substrate; Performing a passivation treatment on a partial area of ​​the conductive substrate, thereby forming an insulating passivation layer on the conductive substrate; Covering the gallium oxide nanorod array with a continuous two-dimensional conductive material, and contacting the two-dimensional conductive material with the insulating passivation layer; A first electrode and a second electrode are respectively manufactured on the conductive substrate and the two-dimensional conductive material.

14. The preparation method according to claim 13, characterized in that include: At least a partial area of ​​the conductive substrate is passivated by ion implantation.

15. A gas detection method, characterized in that include: The gas to be detected is brought into contact with the gallium oxide gas sensor according to any one of claims 1 to 12, and qualitative and / or quantitative detection of the gas to be detected is achieved based on the electrical signal output by the gallium oxide gas sensor; The gas to be detected includes CO, CH4 or O2.

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