Gamma Radiation Effects on The Performance of The CdSe Thin Film for Photodetector Application

Abstract

Cadmium Selenide thin films were deposited on glass substrates and p-type silicon substrates using pulsed laser deposition technique (Nd: YAG laser). Some of these samples were exposed to different intervals (10,20,30,40) days of gamma radiation using a ²²⁶Ra source emitting 186 KeV ?-ray. For comparison purposes, the other diodes were kept without any irradiation. Results have shown all these thin films exhibit a hexagonal structure. However, there is a new (102-SiO₂) peak appeared in the irradiated thin film pattern. The crystallite size of pristine and irradiated CdSe thin films were (26.9,25.8,28.4,35.3 and 22.2) nm respectively, whereas the average grain size of the pristine film was (112.3-29.24) nm whereas for the irradiated films (45.58-33.72) nm, (61.16-42.8) nm, (55.7-36.03) nm and (53.31-43.45) nm. Results also show that the band gap increased from 2.17eV for pristine thin films to 2.28, 2.45, 2.2, and 2.28 eV for the irradiated thin films. also, I-V characteristics show the dark current decreases for the irradiated thin films. The forward current under illumination increases when exposed to small gamma radiation values and then decreases with higher exposure values. In contrast, the reverse current increases with the irradiation.