Enhancement by high gamma radiations of optical and electrical properties of indium oxide thin films for solar devices

Indium oxide (In2O3) thin films were prepared by spray pyrolysis technique on glass substrates. Prepared thin films were irradiated by gamma radiations with various doses 1, 5, 10, and 100 kGy using an industrial gamma 60Co source. Structural, optical photoluminescence, and electrical properties of irradiated thin layers were investigated, respectively, by X-Ray diffraction, Raman spectroscopy, spectrophotometer, fluorescence spectrometer, and Hall effect. Analysis of structural properties of irradiated thin layers has shown that In2O3 thin films exhibit the same cubic structure with the appearance of new plane orientations (400) and (622) besides the initial one (222) with a decrease in grain size. Transmission values of irradiated thin layers show an increase from 77 to 86 % with the presence of more interference fringes. It was found that band gap energy E g decreases from 3.45 eV to a minimum value of 3.08 eV for a γ-dose of 10 kGy. Envelope method was used to determine the refractive index which decreases after exposing to γ-radiations from 3.38 to a minimum value of 1,98. Photoluminescence spectrum depicts a global diminution in intensity peak after irradiation. Besides, measured electrical resistivity shows a strong decrease from 65.02 × 10−2 Ω cm to a minimum value of 1.02 × 10−2 Ω cm for 5 kGy. These results suggest that gamma radiation can improve the physical properties of indium oxide thin films which can be used as transparent conductive electrode or optical window in photovoltaic devices.