Thickness and gamma-ray effect on physical properties of CdO thin films grown by pulsed laser deposition

Abstract

Polycrystalline Cadmium Oxide (CdO) thin films were preparedusing pulsed laser deposition onto glass substrates at roomtemperature with different thicknesses of (300, 350 and 400)nm,these films were irradiated with cesium-137(Cs-137) radiation. Thethickness and irradiation effects on structural and optical propertieswere studied. It is observed by XRD results that films arepolycrystalline before and after irradiation, with cubic structure andshow preferential growth along (111) and (200) directions. Thecrystallite sizes increases with increasing of thickness, and decreaseswith gamma radiation, which are found to be within the range(23.84-4.52) nm and (41.44-4.974)nm before and after irradiation forthickness 350nm and 400nm respectively, The dislocation density,microstrain and number of crystallites per unit surface area,decreases with increasing of thickness, while they increases withgamma radiation. From the atomic force microscope (AFM), thegrain size of CdO films decrease from 96.69nm before radiation to89.49 nm after gamma radiation and RMS roughness increases forthe irradiated sample from 4.26nm to 4.8nm, increase in the surfaceroughness is advantages as it increases the efficiency of the CdOsolar cells. The optical properties for thin CdOfilms with differentthickness before and after gamma irradiation have been determinedand reveals direct energy gap. It is decrease with the increase ofthickness, while it is increase after gamma irradiation. These films apromising candidate for the window layer in solar cells and otherpossible optoelectronic application.