Research On Preparation And Phase Transition Properties Of VO_x Thin Films

The reversible phase transition of vanadium dioxide （VO₂） thin film materialsfrom semiconductor phase to metal phase will occur in the68℃nearby. It mainlymanifests in the phase transition of its electricity, magnetic, optical （terahertz waveband, THz） and other characteristics. This makes it has extensive prospect in theoptical devices, storage areas, and intelligent windows. So how to prepare an excellentperformance of VO₂thin film has been the focus of scholars.In order to achieve a better phase transition effects, the traditional reactionsputtering for preparing vanadium oxide （VO_x） thin film needs the thermal annealingfor general occasions. The difficulties of controlling the ratio of Ar and O₂pressuremake the stability and repeatability of the experiment poor, and the conventionalthermal annealing process also makes the preparation period of the film longer. In thispaper, first of all, to state the preparation of pure metal vanadium （V） thin film in Sisubstrate exploiting magnetron sputtering method. Secondly, to obtain VO_xthin filmthrough the thermal oxidation the obtained metal V thin film combined with rapidthermal annealing process （RTP）. The advantages of this technology craft lie in that itnot only makes thermal annealing and thermal oxidation become one, but alsoadopting RTP process which will on the one hand greatly shorten the wholeexperimental period and save the regulation of Ar and O₂pressure ratio that is noteasy to control, on the other hand, make the whole process simple, fast andcontrollability good.As for the prepared VO_xfilm, analyze its crystal structure, the film of V valencestate and component and surface microstructure using the X-ray diffractometer （XRD）,X-ray photoelectron spectroscopy （XPS） and scanning electron microscope （SEM）.Test its electrical and optical properties of the sample applying four point probe testmethod and THz time domain spectrum technology （THz-TDS）. It turns out that wecan prepare VO_xthin film with the characteristics of thermally induced phasetransition at some extend of RTP insulation temperature and time, the thin film squareresistance changes are more than two orders of magnitude after the phase transition,and the thin film is mainly composed of V2O5and VO₂blend composition. Fordifferent thickness of the VO_xthin film, sputtering metal V time in20-40minutes range can receive the best performance phase transition. For the thin film of sputteringmetal V time in20minute, the phase transition characteristic is best when the RTPcondition is under500℃and25s, it also can modulate the THz wave to a certainextent. Moreover, the phase transition mechanism of thermally induced and photoinduced could not happen at the same time, so they do not have a correspondingrelationship.