Titanium Dioxide Thin Films As Vacuum Ultraviolet Photoconductive Detectors With Enhanced Photoconductivity By Gamma-Ray Irradiation

We show that titanium dioxide (TiO2) thin films can be used as photoconductive detectors of vacuum ultraviolet (VUV) radiation, with further improvement in performance after recovery from gamma ray irradiation. An initial decrease in photocurrent was observed after irradiation with 3.4 kilo gray gamma rays as oxygen vacancies and trivalent titanium ion states are formed as confirmed by optical and photoluminescence spectroscopies showing a red-shift in the transmission edge, narrowing of the optical band gap, and appearance of a broad absorption band in the 392-528 nm wavelength range. Subsequent recovery of these defects increased the photoconductivity beyond what was displayed by the pristine detector. After recovering, the photosensitivity of the detector increased by a factor of about 8 and 124 compared to its photosensitivity before and immediately after irradiation, respectively. As the applications of VUV light continue to grow and development of light sources progress, there is increased demand for detectors in this short wavelength region. Our results demonstrate the potential of TiO2 thin films as VUV detectors including the use of gamma ray irradiation as post-fabrication treatment for improved photoconductivity.