PHOTOCHROMIC PROPERTIES OF AMORPHOUS WO3 FILMS

The phoochromic properties of vapor-deposited amorphous tungsten oxide (a-WO3) films have been studied from the viewpoint of their dependence on film structure and water content in the films. The a-WO3 films, prepared under different deposition conditions and postannealing temperatures, were irradiated with uv light (366 nm) at room temperature in vacuum, and the increase in the absorbance of the films was measured. After irradiation for 200 days, the saturation of absorbance was observed for all films, The crystallinity of the framework structure, packing density and total water cohntent were estimated using Raman spectroscopy, X-ray fluorescence and Fourier transform infrared (FTIR) spectroscopy, respectively. Decreasing saturated absorbance of the films was observed with increasing density and decreasing crystallinity of the films.