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

Abstract

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 α-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. γ-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 α-WO₃ phase