Structural and optical properties of Dy doped ZnO thin films prepared by pyrolysis technique

Structural, optical and Raman scattering studies have been performed on the Dy substituted zinc oxide (ZnO) thin films (1, 3 & 5 wt%) fabricated through a sol gel based spray pyrolysis technique on preheated glass substrates. The hexagonal crystal structure with (002) preferred orientation was confirmed from the X-ray diffraction analysis for the undoped and Dy doped ZnO films. The crystallinity of the films decreased with increasing Dy content with a corresponding decease in the intensity of (002) orientations. Reduction in grain size with increase in Dy content was observed. The shift of E-2 (high) mode observed in the Raman spectra towards the lower wave numberswith increase in Dy concentration was correlated with the increase in stress on the ZnO matrix upon Dy substitution. The optical band gap was found to increase from 3.17 eV to 3.27 eV with a transparency of 80% for higher Dy concentrations. A blue shift in the NBE emission was also observed for Dy doping.