Preparations And Properties Of The Thermosensitive Vanadium Dioxide Thin Films

Vanadium dioxide is a kind of thermo-sensitive functional material which changes itsphase reversibly from semiconductor to metal status and accompanies with an abruptchanges in its electrical and optical properties at68℃while heated. It has a wideapplication in many technological fields, such as photo electric switch, optical storage,uncooled infrared detector, intelligent window and so on. The preparing methods andperformances of VO₂thin films have been the researching focuses.The first chapter describes the crystal structure, the phase transformation mechanism,and the applications of VO₂thin film. It also describes the applicable prospects of VO₂thinfilm as a new type of functional thin film materials.The second chapter describes the preparing methods of VO₂thin film. It focuses on thecoating mechanism of the reactive magnetron sputtering and the experimental process ofthe preparing VO₂thin film as well as the characterization techniques used in ourexperiments.Chapter3studies the DC magnetron sputtering processes prepared VO₂thin films. Itfocuses on the influence of partial pressure of oxygen, sputtering time and differentsubstrates on the phase transformation and properties of prepared VO₂thin films. Theexperimental results show with the gas pressure of1.5Pa, the power of100W, the sputteringtime of1hour, the partial pressure of oxygen is3%after annealing in argon at450℃for2hours, the phase transition of the VO₂thin film sample is better, it contains more VO₂phase.With the decreasing of the sputtering time the visible light transmittance of the VO₂thinfilm is increased.Chapter4studies the processes of the W doped VO₂thin films and the Ti doped VO₂thin films prepared by direct current/radio frequency reactive magnetron co-sputtering, andthe N doped VO₂thin films prepared by the DC magnetron sputtering at that the N2is usedas for the dopant source. The experimental results show that the phase transitiontemperature of W-doped VO₂thin film is reduced to37℃, however, the phase transitiontemperature of Ti-doped VO₂thin film is increased to67℃, and the phase transitiontemperature of N-doped VO₂thin film is55℃. The phase transitions of the VO₂thin filmsare changed after doping.In chapter5the TiO₂/VO₂double bilayer were prepared by DC magnetron sputtering,The influences of the TiO₂buffer layers of different process parameters on the phases and properties of prepared VO₂thin films have been studied. Based on the research results, theTiO₂buffer layers were deposited on glass substrate by magnetron sputtering equipment,next W-doped VO_Xthin films were deposited on them by direct current/radio frequencyreactive magnetron co-sputtering, and then they were annealed under nitrogen atmosphere.The W-doped VO₂thermosensitive intelligent glasses that based on the TiO₂buffer layershave been prepared. The results show that when the sputtering gas pressure is1Pa, thepartial pressure of oxygen is20%, and the DC power of Ti target is100W, the W-dopedVO₂thin film has a dense and homogeneous size, and the phase transition temperature ofW-doped VO₂thin film is reduced to35℃，the visible light transmittance is high,and theshielding effect of infrared transmittance is obviously.