Microstructural and optoelectronic properties of diluted magnetic semiconducting Cd1−xFexS nanocrystalline films

Abstract

We report the preparation of electron beam evaporated Fe-doped CdS nanocrystalline thin films (Cd1−xFexS) with different doping concentrations (x=0.002, 0.05, 0.1, 0.15 and 0.2) and characterization of their microstructural and optoelectronic properties. The structural properties investigated by X-ray diffraction revealed cubic zincblende CdS type structure and a decrease of lattice parameter with Fe doping confirming incorporation of Fe in Cd atom positions. The crystallite size of the films was found to vary from 33 to 20nm with increasing Fe content. The elemental chemical stoichiometric was studied by energy dispersive X-ray analysis. The optical characterization of the films has been carried out from spectral transmittance and reflectance obtained by double beam spectrophotometer in the wavelength range from 190 to 2500nm. The refractive index and extinction coefficient have been found to increase with increasing Fe content. The increase in the refractive index has been explained on the basis of polarizability. Dispersion of refractive index has been analyzed in terms of the Wemple–DiDomenico single oscillator model. The oscillator parameters; the single oscillator energy E0, the dispersion energy Ed, the static refractive index n0, average interband oscillator wavelength λ0, and the average oscillator strength S0 were estimated. It was further found that the optical energy gap decreases from 2.470eV to 2.338eV with increasing Fe content from x=0.002 to x=0.2 which is suggested to be related to the sp–d exchange interaction with the Fe2+ magnetic moments.