GAMMA RADIATION INDUCED EFFECTS IN METAL OXIDE THIN FILMS FOR RADIATION DOSIMETRY

Abstract

Studies on changes in current and optical band gap of thin films of metal oxides due to gamma irradiation have been gaining increasing attention, due to their extensive use in real-time gamma radiation dosimetry. This work aims to study the optical properties of metal oxides thin films exposed to gamma radiation by using thin films of different metal oxides. The optical characteristics for the gamma irradiated and as-deposited thin films were analysed to obtain Variation of the normalized energy width of band tails of the localized states with the gamma radiation dose plots at different applied voltages. The report explains the variation in various properties of Zinc Oxide and Tellurium Dioxide thin films when thermally annealed in air and exposed to gamma radiation using 137Cs and "Co sources. The results on optical band gap of thin films before and after gamma irradiation as well as on thermally annealed thin films clearly show decrease in the optical band gap with thermal annealing and with increase in the dose of certain value. However, decrease of the optical band gap is observed above this dose limit. The optical properties of annealed films for zinc oxide have shown a variation in the band gap between 2.94 eV and 3.37 eV and for tellurium dioxide have shown a variation in the band gap between 3.46 eV and 3.8 eV. The IN data were studied to get current versus dose for various values of applied voltages. The results have clearly revealed an increase in the current density near linearly with the dose of certain value and decrease more than this level. The enhancement in current is because of decrease of the optical band gap and the decrease in the current after certain limit can be - attributed to the increase of optical band gap and the formation of the clusters.