The electronic structure of tungsten oxide thin films prepared by pulsed cathodic arc deposition and plasma-assisted pulsed magnetron sputtering

Pulsed cathodic arc and pulsed magnetron sputtered WO3 thin films were investigated using electron microscopy. It was found that the cathodic arc deposited material consisted of the alpha-WO3 phase with a high degree of crystallinity. In contrast, the magnetron sputtered material was highly disordered making it difficult to determine its phase. Electron energy-loss spectroscopy was used to study the oxygen K edge of the films and it was found that the near-edge fine structures of films produced by the two deposition methods differed. The oxygen K-edge near-edge structures for various phases of WO3 were calculated using two different self-consistent methods. Each phase was found to exhibit a unique oxygen K edge, which would allow different phases of WO3 to be identified using x-ray absorption spectroscopy or electron energy-loss spectroscopy. Both calculation methods predicted an oxygen K edge for the gamma-WO3 phase which compared well to previous x-ray absorption spectra. In addition, a close match was found between the oxygen K edges obtained experimentally from the cathodic arc deposited material and that calculated for the alpha-WO3 phase.