Oxygen partial pressure and thermal annealing dependent properties of RF magnetron sputtered TiO2−x films

TiO2−x thin films were deposited on unheated SiO2/Si substrates by RF reactive magnetron sputtering at different oxygen partial pressures (pO2). The structural properties of the films were characterized by Grazing incident X-ray diffraction (GIXRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The FE-SEM images exhibited dense and smooth film surfaces likely due to the limited ability of adatoms to migrate on the substrate at room temperature. The indirect and direct optical band gaps of TiO2−x films shift towards higher photon energy with increasing pO2. In order to optimize the thermal stability of structural and electrical properties, the as-deposited films were annealed at 300 °C in air atmosphere. But, no significant variations were observed in structural and morphological properties compared to as-deposited films, due to the low surface mobility and distant growth temperature of Titania crystallization. However, sizeable distinction in electrical resistivity behaviour was observed in annealed TiO2−x films. Finally, it was found that a higher resistivity causes a higher activation energy and then higher TCR value.