Study On Fabrication And Methane Gas Sensitivity Performance Of VO₂ Thin Films

vanadium dioxide?VO₂?is a kind of metastable vanadium oxides which is composed of V and O.Under the excitation of light and heat,VO₂ undergoes a reversible metal-insulator transition with the transition temperature of 68? which is close to room temperature,so it is widely investigated by researchers.Taking advantage of the phase transition characteristics of VO₂ thin film in electronic and optical aspect,it is applied to smart windows,optical switches,phase change memory,etc.Study shows that the high phase transition amplitude and low phase transition temperature of VO₂ thin film can improve device performance.Recent studies have found that VO₂ thin film is not only a kind of perfect heat sensitive material,but also gas sensitive material which is used as methane gas sensor.In this paper,Contents of this paper include two aspects: One is the fabrication of vanadium oxide?VO_x?thin film which possesses high phase transition amplitude and low phase transition temperature;the other is the effect that microtopography and noble metal doping of VO_x thin film on the methane gas sensor.The microscopic analysis,electrical and gas sensing performance of VO_x thin film are researched by X-ray diffraction?XRD?,field emission scanning electron microscope?FESEM?,four-point probe resistivity measurement system and gas sensor test equipment.For the first part of the research content,VO_x thin film is obtained by magnetron sputtering and rapid thermal processing.In the experiment,with the single variable method,VO_x thin film which has the property of high phase transition amplitude and low phase transition temperature is grown by adjusting the annealing parameters.The experiment found that the phase transition amplitude of VO_x thin film can up to more than two order of magnitude and the phase transition temperature is 46 ? which is far lower than 68 ?when the annealing temperature was 460 ?,annealing time was 270 s and annealing oxide flow rate was 5slpm.Increasing the surface area of VO_x thin film and doping noble metal are the main methods to improve the methane gas sensing performance.In terms of optimizing the thin film surface area,changing the substrate temperature in sputtering and doping Cu are two ways to increase the surface area.The result shows that the surface area of VO_x thin film is biggest after V thin film with the substrate temperature being 400 ?and spraying Cu is annealed,and it shows the methane gas-sensitive reaction.And when the film surface is dopped Pt,compared to pure VO_x thin film,its sensitivity to methane increases and can be done at room temperature,which has great importancefor reducing gas sensors operating temperature.Pt doping is more effective than optimizing surface morphology for enhancing methane gas sensing performance.The thing that VO_x is used to test CH4 not only extends the applied range of VO_x thin film,but also has practical significance for the greenhouse effect and gas explosion.