Room temperature NO2 sensing properties of reactively sputtered TeO2 thin films

Tellurium oxide (TeO2) thin films were deposited on quartz substrates by sputtering a Te metal target in an Ar + O-2 gas mixture. The structure and phase identification of the samples were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The as-deposited films were amorphous and became crystalline after thermal annealing at 500 degrees C. The optical energy gap of the films was determined from transmittance and reflectance spectra. The direct energy gap values were found to be 3.81 eV in as-deposited films and 3.73 eV in thermally annealed samples. Properties of the TeO2 thin films for NO2 gas sensing at room temperature were also investigated. The as-deposited films showed negligible sensitivity to NO2 gas. On the contrary the films prepared by thermal annealing showed a promising sensitivity and response towards tested gas. (C) 2008 Elsevier B.V. All rights reserved.