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

摘要

Nanostructured titanium oxide (nano-TiO_x) 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 TiO_x thin film deposited at room temperature is amorphous. A mixture of anatase and rutile nanocrystalline structure phase were present in oxygen annealed TiO_x 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 TiO_x thin film. The X-ray photoelectron spectra reveals Ti~(3+) and Ti~(4+) ions are coexisting in TiO_x films. The optical spectra of the films indicate that the optical absorption edge of the nano-TiO_x film exhibits a red shift compared to the as-deposited film. Furthermore, compared to bulk TiO_x, 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 TiO_x thin film increase significantly after annealing in oxygen.