Study on photochromic properties of WO 3 thin films as optical sensors

Abstract

WO 3 thin films have been widely studied because they exhibit the electrochemistry effect i.e. a reversible change of color when in contact with an electrolyte and under bias or light illumination which can be used in smart windows and displays. In this work, the optical properties of tungsten oxide films prepared by DC reactive magnetron sputtering and sol-gel method were investigated. The transmittance of the samples was investigated by double-beam UV-VIS-NIR spectrophotometer respectively. The transmittance of the samples changed greatly with wavelength in the range from 250nm to 350nm and was a minimum at about 280nm. The transmittance of samples prepared by sol-gel is better than that by DC reactive magnetron. Molecular structure and surface morphology of samples were obtained by AFM. Film materials prepared by DC reactive magnetron sputtering method are evener and compacter than those by sol-gel method. The molecular of sample by sol-gel is obvious tetrahedron and the molecular of sample by DC reactive magnetron tends to be planar constructure. The chemical bonds of W-O and O-O of the samples are about 0.5nm and 0.6nm long respectively.