On the optical properties of Ag^{+15} ion-beam irradiated TiO_{2} and   SnO_{2} thin films
  The effects of 200-MeV Ag^{+15} ion irradiation on the optical properties of TiO_{2} and SnO_{2} thin films prepared by using the RF magnetron sputtering technique were investigated. These films were characterized by using UV-vis spectroscopy, and with increasing irradiation fluence, the transmittance for the TiO_{2} films was observed to increase systematically while that for SnO_{2} was observed to decrease. Absorption spectra of the irradiated samples showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with increasing irradiation fluence for TiO_{2} while significant changes in the direct bandgap from 3.92 to 3.6 eV were observed for SnO_{2}. The observed modifications in the optical properties of both the TiO_{2} and the SnO_{2} systems with irradiation can be attributed to controlled structural disorder/defects in the system. 
Hardeep Thakur, Sanjeev Gautam, P. Thakur, K. K. Sharma, Abhinav   Pratap Singh, Yogesh Kumar, Ravi Kumar and Keun Hwa Chae
cond-mat.mtrl-sci physics.acc-ph