Optical absorption in co-evaporated V₂O₅-TeO₂ thin films

Abstract

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.