Electrical and optical properties of reactive sputtered TiOx thin films for uncooled IR detector applications

Nanostructured titanium oxide (nano-TiOx) thin films for uncooled IR detectors were fabricated by dc reactive magnetron sputtering and post-deposition annealed in oxygen atmosphere. The crystalline structure and surface morphology were characterized by glancing incidence X-ray diffraction (GIXRD) and field emission scanning microscopy. The results of GIXRD measurements indicate that TiOx thin film deposited at room temperature is amorphous. A mixture of anatase and rutile nanocrystalline structure phase were present in oxygen annealed TiOx thin film. A weak absorption peak around 438 cm−1 corresponding to Ti–O stretching vibration is observed by Fourier transform infrared spectroscopy with annealed TiOx thin film. The X-ray photoelectron spectra reveals Ti3+ and Ti4+ ions are coexisting in TiOx films. The optical spectra of the films indicate that the optical absorption edge of the nano-TiOx film exhibits a red shift compared to the as-deposited film. Furthermore, compared to bulk TiOx, a blue shift was observed in both of the deposited and annealed films due to quantum size effect. The dependence of resistivity on temperature reveals both the absolute value of temperature coefficient of resistivity (TCR) and activation energy of TiOx thin film increase significantly after annealing in oxygen.