OPTICAL-ABSORPTION IN COEVAPORATED V2O5-TEO2 THIN-FILMS

The electron diffraction pattern shows that co-evaporated V2O5-TeO2 thin film samples are amorphous at room temperature and become polycrystalline at temperatures higher than about 513 K. This behaviour is similar to that of amorphous V2O5 thin films. The optical absorption edge of amorphous thin films of V2O5-TeO2 is studied in the wavelength range 200 to 900 nm and the FTIR spectra are studied in the wave number range 400 to 4000 cm-1. The FTIR spectra of amorphous V2O5 thin film are found to be similar to those of amorphous V2O5-TeO2 thin films. This suggests that the coordination number of the vanadium ion in V2O5-TeO2 is the same as that in crystalline V2O5, and thus the optical absorption edge of amorphous V2O5-TeO2 thin films can be described by direct forbidden transitions.