Development of a real-time gamma dosimeter of high sensitivity

Aiming to develop a real-time gamma dosimeter with high sensitivity, we have studied in detail the gamma radiation induced changes in the structural, optical and electrical properties for the thin films of tellurium dioxide as well as for the thin films of the mixture of indium oxide (In 2 O 3 ) and tellurium dioxide (TeO 2 ). The thin films of different thicknesses of these materials were prepared by thermal evaporation in vacuum. The XRD patterns show that the as deposited thin films as well as the thin films exposed to different levels of gamma radiation dose are amorphous in nature. The optical characterization of the as deposited thin films and the thin films exposed to various levels of gamma radiation dose clearly show that the optical band gap decreases with the increase of dose up to a certain value. The current-voltage characteristics for the as deposited thin films as well as for the thin films exposed to different levels of gamma radiation dose show that the current increases near linearly with the dose over a wide range of doses. In fact, at different applied voltages, the current has been observed to increase quite linearly with the gamma radiation dose over a wide range of doses. Further, the range of doses is higher for the thicker films. The near linear increase of the current with the gamma radiation dose can partly be attributed to the decrease of the optical band gap with the gamma radiation dose. Employing dose dependence of the current, the real-time gamma dosimeters based on TeO 2 thin films of thicknesses 300, 450 and 600 nm have been found to possess sensitivity in the range 6 – 26 mA/cm 2 /Gy and those based on the thin films of In 2 O 3 /TeO 2 mixture of thicknesses 300 and 600 nm have been found to possess sensitivity in the range 29 – 130 mA/cm 2 /Gy.