Effect of gamma radiation on electrical and optical properties of (TeO2)0·9 (In2O3)0·1 thin films

Abstract

We have studied in detail the gamma radiation induced changes in the electrical properties of the (TeO 2 ) 0·9 (In 2 O 3 ) 0·1 thin films of different thicknesses, prepared by thermal evaporation in vacuum. The currentvoltage 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 μ μ μGy/μ μ μA/cm 2 . These values are far superior to any presently available real-time gamma radiation dosimeter.

Effect of Gamma Irradiation on the Structural and Optical Properties of ZnO Thin Films

“…The decrease in band gap shows that the irradiated film causes a slightly 'red shift' in the optical spectra. This decrease in the optical band gap is basically due to the increase in the energy width of the band tails of localized states, similar observations have also been reported by other worker [17][18][19]. The absorption coefficient near the band edge shows an exponential dependence on photon energy [20]:…”

Influence of gamma ray irradiation and annealing temperature on the optical constants and spectral dispersion parameters of metal-free and zinc tetraphenylporphyrin thin films: A comparative study

“…During γ-ray irradiation, the defects are created within the thin film. At the same time, the defects also get annihilated even under the normal room temperature conditions [39,40]. This creation and annihilation of defects coexist together and at higher doses of γ-ray irradiation, the number of defects created due to γ-ray irradiation equals the number of defects annihilated [40].…”

Study of radiation effect and bismuth content on the physical properties of some chalcogenides based on selenium

“…Sharma and Maity [28] reported that the optical band gap was found to decrease after γ-irradiation. This decrease in the optical band gap is due to the increase in Urbach tails.…”

“…Zhu [29] supposed that ionizing radiation causes structural defects which intern leading to a change in their density upon exposure to γ-ray. The produced free electrons as a result of band-to-band transitions are trapped in ion vacancies which in turn is the cause of formation of color center leading to increase the electrical conductivity [28,29]. Therefore, the decrease in the optical band gap is essentially due to the increase in Urbach tails [30].…”