Tungsten oxide films by reactive and conventional evaporation techniques

Tungsten oxide films (WO(3)) are deposited by thermal evaporation techniques using the starting materials of tungsten (W) and tungsten oxide (WO(3)). By varying deposition parameters, three main types of WO(3) film exhibiting different optical properties form. These are blue, gray, and colorless films. The samples are characterized optically and morphologically. Blue-colored samples exhibit a broad selective absorption peak around 1000nm. Absorption of gray-colored samples spreads out in the visible region in an exponential form. The refractive indices of samples are between 1.9 and 2.1. The energy gap of blue and colorless samples is 3.32 eV, but that of the gray-colored samples is 3.18 eV and smaller. X-ray diffraction studies reveal that evaporated WO(3) films are amorphous. Fourier transform infrared spectra of samples were studied to evaluate bond properties. Colorless near-stoichiometric tungsten oxide films exhibit three absorption peaks in the 1000-600-cm(-1) window. These peak locations, in terms of cm(-1) window. These peak locations, in terms of cm(-1), are 669,737, and 813. In the colored samples, these three absorption peaks split into two peaks ~20 cm(-1) apart.