Effects of gamma irradiation on electrical, optical and structural properties of tellurium dioxide thin films

Abstract

Effects of gamma irradiation on electrical, optical and structural properties of the TeO₂ thin films of different thicknesses, prepared by thermal evaporation in a vacuum, have been studied in detail for a much wider range of doses than made here-to-fore. The current density increases near linearly with gamma radiation dose up to a critical dose, a quantity higher for thicker films and decreases thereafter. The optical band gap decreases with the gamma radiation dose at low doses. At higher radiation doses, however, the optical band gap has been observed to increase. The FESEM images show that the as-deposited thin films are non-uniform, the exposed thin films become more and more uniform with the increase of the gamma radiation dose showing partial healing of the intrinsic defects. The formation of the large sized clusters with voids takes place in the films exposed to higher radiation doses. The increase of the current density with the gamma radiation dose at low doses may be attributed partly to the lowering of the optical band gap and partly to the healing effect. At higher radiation doses, however, the decrease in the current density may be attributed partly to the rising of the optical band gap and partly to the formation of the large sized clusters having voids.