Properties of crystalline γ-TeO2 thin film

Thin films of tellurium dioxide (TeO2) were prepared by RF diode sputtering at room temperature (RT). The effects of post-deposition annealing in temperature range RT to 400 °C on the structural and optical properties of the deposited thin films were studied. The films were characterized using X-ray diffraction, infrared (IR) absorption spectroscopy, Raman spectroscopy and ultraviolet–visible (UV–vis) transmittance measurement. The as-deposited thin films are amorphous and become crystalline after a post-deposition annealing temperature of 400 °C. IR spectroscopy reveals the formation of Te–O bond. Raman spectroscopy depicts the formation TeO4 disphenoid for as-deposited TeO2 films. The phonon modes were found to shift towards low frequency along with the appearance of an additional sharp mode after post-deposition annealing, indicating the formation of crystalline TeO2 thin film in γ-phase.