ELECTRON-ENERGY-LOSS NEAR-EDGE SPECTROSCOPY OF OXYGEN IN AMORPHOUS AND CRYSTALLINE WO3 AND MOO3

EELS has been used to measure the low loss and oxygen K-edge spectra of crystalline WO3 and MoO3 and amorphous W and Mo oxide thin films prepared by electron-beam evaporation. The O K-edge spectra all show a sharp peak at the edge onset. Using a molecular orbital approach, this first peak has been identified as a t(2g)(*) band, consistent with the band structure of c-WO3 calculated by Bullett. In the amorphous oxides, the first peak is reduced and higher energy peaks are broadened. The O K-edge spectra of a-WO3-x after beam damage show further reduction of the first peak, and are very similar to the spectrum for coloured a-WO3 observed by Hashimoto.