Effect of gamma radiation on electrical and optical properties of (TeO2)0.9 (In2O3)0.1 thin films

We have studied in detail the gamma radiation induced changes in the electrical properties of the (TeO2)(0.9) (In2O3)(0.1) thin films of different thicknesses, prepared by thermal evaporation in vacuum. The current-voltage characteristics for the as-deposited and exposed thin films were analysed to obtain current versus dose plots at different applied voltages. These plots clearly show that the current increases quite linearly with the radiation dose over a wide range and that the range of doses is higher for the thicker films. Beyond certain dose (a quantity dependent on the film thickness), however, the current has been observed to decrease. In order to understand the dose dependence of the current, we analysed the optical absorption spectra for the as-deposited and exposed thin films to obtain the dose dependences of the optical bandgap and energy width of band tails of the localized states. The increase of the current with the gamma radiation dose may be attributed partly to the healing effect and partly to the lowering of the optical bandgap. Attempts are on to understand the decrease in the current at higher doses. Employing dose dependence of the current, some real-time gamma radiation dosimeters have been prepared, which have been found to possess sensitivity in the range 5-55 mu Gy/mu A/cm(2). These values are far superior to any presently available real-time gamma radiation dosimeter.