Optical and Structural Properties of Copper Doped CdS Thin Films Prepared by Pulsed Laser Deposition

This paper presents the study of the structural and optical properties of copper doped cadmium
sulde thin lms prepared by pulsed Nd:YAG laser. The copper concentration in the targets was
varied from 0.05% to 5% in weight and they were heated at a temperature of 500C in air for
one hour. It was observed that annealing un-doped and doped thin lms at temperatures above
160C leads to an abrupt increase in the optical transmission, changing from dark brownish to
transparent yellowish. For annealed samples at 300C, increasing Cu concentration from 0.0%
to 2%, leads to an increase in the optical transmission up to 80%, at a wavelength of about 700
nm. XRD patterns showed the hexagonal phase of cadmium sulde and a number of CdO peaks
relating to the partial oxidation of cadmium. The XPS spectra of the annealed samples indicate
an accumulation of Cu at the surface. Therefore, Cu impurity can enhance CdS oxidation and
the size of the crystallites. The highest value of the photo-current for the samples is related to
the lowest Cu concentration, i.e: 0.05%.