Study On Phase Transformation And Doping Mechanism Of Vanadium Dioxide Materials

Vanadium dioxide material has a reversible phase transition phenomenon in semiconduc-tor metallictiy.The phase transition process is accompanied by changes in crystal structure,transmittance and resistivity,it is widely used in electromagnetic shielding,absorber and oth-er fields.The main research content of this paper:Vanadium dioxide thin films were prepared by inorganic sol-gel method and magnetron sputtering method respectively,and the characterization of the prepared samples was tested by X-ray diffraction.The effects of annealing temperature,annealing time and vacuum degree on the preparation of Vanadium dioxide samples were studied and explored by sol-gel method.When annealing temperature is 540℃,vacuum degree is 20-35Pa,annealing time is 140min,the samples prepared are better.When oxygen/argon ratio is 3:20,annealing temperature is500℃,annealing time is 2h,vacuum degree is 0.01Pa,the magnetron sputtering method is used to prepare VO₂thin films successfully.The crystal structure and band gap of vanadium dioxide were simulated by density functional theory.Based on density functional theory,the field-induced phase transition of vanadium dioxide under field excitation is studied.The temperature of phase transition of VO₂can be adjusted by field-induced phase transition.Field-induced phase transition test was carried out on the film.At room temperature,when the voltage was about 100V,the vanadium dioxide film underwent phase transition and the resistance change was about 10⁴orders of magnitude.The regulatory mechanism that doping can change the phase transition temperature of VO₂was studied,and the structure,band gap and optical properties of doped vanadium dioxide with different atoms were simulated.When vanadium dioxide is doped with chromium,molybdenum and tungsten,its structure,band gap and optical properties are simulated.When VO₂is doped with molybdenum atom,its structure is the most stable,its phase transition temperature is the lowest,and the corresponding band gap value is 0.551e V,which has the least influence on visible light transmittance.A new type of tunable absorbing body was designed by using molybdenum doped vanadium dioxide as metasurface.The absorbing body was studied from the aspects of different dielectric materials and thickness,thickness and area of top material,and different polarization wave incident.It is concluded that the absorption rate of the VO₂-doped solid rectangular body is 99.28%at 7.13THz,and the bandwidth of the absorption rate greater than20%is 1.63THz.When the VO₂-doped structure is four open rings,the absorptivity of the absorber at 8.47THz is up to 99.79%,and the bandwidth with absorptivity greater than 20%can reach 2.71THz.