Investigation of refractive index dispersion parameters of Er doped ZnO thin films by WDD model

Abstract

The goal of this work is to investigate the effect of erbium ion substitution on the optical properties of ZnO thin film. Thin films of 0, 0.5, 1 and 1.5 at% erbium doped ZnO were deposited on glass substrate using sol-gel method. X-ray diffraction pattern was used for structural study. All the films show a polycrystalline nature with only a slight shifting of peaks. Optical properties of films have been investigated by spectroscopic ellipsometry. The frequency response and changes in optical parameters are the main focus of this paper. For the physical description of dispersion parameters Wemple–DiDomenico (WDD) single oscillator model was used. This model shows the single oscillator behavior of all the thin films. There is a slight increase in static refractive index with the increase in erbium concentration. However, refractive index obtained from the fitting of spectroscopic ellipsometry data shows an appreciable increase in optical region. Dispersion energy Ed that measures the strength of inter-band transition was also found to increase with the doping concentration of erbium ion. Real part of dielectric function was increases with the increase in photon energy for all the thin films.