First-principles Calculation And Experimental Study On Phase Transiton Performance Of Doped VO₂

Vanadium dioxide（VO₂）undergoes reversible insulator metal transition（IMT）at 68℃,which leads to great changes in its optical,electrical,magnetic and other physical properties.It is considered to be one of the most promising intelligent thermal control materials.However,the phase transition temperature of 68℃is difficult to meet the requirements of intelligent thermal control of spacecraft electronic devices.Therefore,it is particularly important to prepare VO₂ thin films with phase transition temperature within the working range of spacecraft electronic devices.This paper focuses on the regulation of VO₂ phase transition temperature.Based on the first principles calculation,the influence of 30 kinds of doped elements on the phase transition temperature of VO₂ was investigated,and the doped elements with phase transition temperature close to 25℃were selected.The doped VO₂ thin films with phase transition temperature of 25℃and narrow thermal hysteresis width were prepared by magnetron sputtering.The results show that the phase transition temperature of VO₂ decreases with the volume expansion of monoclinic VO₂ and the decrease of band gap.The doping content of 2%W atoms can reduce the phase transition temperature to27℃and the band gap to 0.41 e V,which leads to the red shift of absorption band to 3μm and the decrease of solar absorption coefficient.It is an ideal doping element for spacecraft thermal control.Tungsten doping increases the density of nucleation defects and promotes the nucleation of VO₂ grains,resulting in the decrease of thermal hysteresis width from 15℃to 8℃.Accurate doped targets can be prepared by hot pressing sintering,and tungsten doped VO₂ thin films can be prepared by RF magnetron sputtering,which are basically consistent with the target composition.Accurate doped VO₂ thin films with high content of V⁴⁺are prepared.The problem of oxygen partial pressure in reactive DC magnetron sputtering and the problem of reducing V⁴⁺in dual-target magnetron sputtering are solved,and the experimental results are basically consistent with the calculation results.The reliability of the calculation is proved.This will provide a theoretical basis for the development of new smart thermal control materials and a new preparation method for doped VO₂ thin films.