Electron beam and gamma irradiation effects on amorphous chalcogenide SbSe 2.5 films

Abstract

In this article, the effects of the electron-beam and gamma irradiation on the features of chalcogenide SbSe 2.5 films have been studied. The films showed an amorphous to partially crystalline phase at doses ranging from 3 to 12 kGy. Optical absorption measurements have been performed where the results reflected a great dependence of the fundamental absorption edge on the irradiation dose. The radiation induced allowed indirect transition with a decrease in the energy gap as the dose increased. The decrease in the gap was a little higher for electron than that for gamma irradiation. This behavior is believed to be associated with the generation of excess of electronic localized states. The change in the optical gap may be explained in terms of diminution of disorder, defects in the structural bonding and crystal field mechanism. Moreover, the characteristic features of the irradiated films have been studied using scanning electron microscope. SEM observation showed a grain growth on the film surface through which the surface morphology has been demonstrated. Accordingly, a structural model concerning the configurational coordinate has been proposed, based on the assuming tri-coordinated Sb atoms and di-coordinated Se atoms, that confirmed the information obtained from the scanning electron microscope. So, Sb–Se bonds in pyramidal form of molecules with excess of Se rings have been formed as a result of irradiation process.