Research On The Optical Properties Of Nanostructure Tungsten-doped VOx Film

VO2(vanadium dioxide) is a kind of phase-transformation material. It shows a specialcharacteristics of semiconductor-metal transition during which its crystal structure transfersfrom monoclinic at low temperature to tetragonal at high temperature. And also its opticalproperties go through a dramatic change. At low temperature much infrared spectrum can gothrough it while it will reflect much infrared spectrum at high temperature. Besides, it’sreversible. Based on this, VO2is a promising functional material applied in such areas assmart windows, optical/electrical switch, optical storage and also becoming a hot subject.This paper aims to research the properties of VO2deposited at different process conditionsand measure its other characteristics using AFM, XRD, and etc..The main content is dividedinto two parts:1. The variation of film characteristics with the change of oxygen partial pressure. It’sfound that the higher the oxygen partial pressure is, the lower the roughness of the filmsurface is. Also, the deposition rate decreases with the increase of the oxygen partial pressure.The composition of the films is different from each other. It’s easy to get VO2at low oxygenpartial pressure while to get V4O9and V7O13at high oxygen partial pressure. Besides, theinfrared transmittance increases with the increase of the oxygen partial pressure. VO2has ahigh absorption while V4O9and V7O13have high reflection. In the last, the annealing processis analyzed using a method of before-annealing vs after-annealing. It is found the annealingprocess has little influence to the undoped film.2. The VOx/W/VOx film is obtained through the sandwich structure, in which the tungstenlayer is used as a functional layer. The thickness of functional layer can be controlled byadjusting the doping time of the inner tungsten layer. It is found that the roughness of the filmsurface is enlarged with the increase of the thickness of functional layer. The tungsten layerhas a thickness of10~50nm (in the nano range). XRD shows that some tungsten oxidesappear in the VOx/W/VOx film after annealing. Also, The intensity of WO0.92(1014) andV7O13(213) both increase with the thickness of functional layer. Remarkably, the infraredtransmittance shows an obvious decline with the increase of the thickness of functional layer.Finally, through the comparison of before and after annealing(500℃/60min,high vacuum), it’sfound the annealing process obviously improve the infrared transmittance of thetungsten-doped VOx film.