Optical and structural properties of nanoscale undoped and cerium doped ZnO with granular morphology

Abstract

Nanoscale undoped and cerium (Ce) doped zinc oxide (ZnO) thin films have been synthesized by sol gel spin coating technique on glass substrate with optimum post annealing temperature of 375 °C. We have investigated that incorporation of cerium in ZnO could alter the morphological, optical and photoluminescence properties of the deposited samples. The X-ray diffraction spectrum reveals that all the synthesized samples have hexagonal wurtzite structure and show strong peak preferentially oriented along the (002) c-axis direction of the substrate. The crystalline size of undoped and Ce doped ZnO thin films were deduced to be 30 and 15 nm respectively, which signifies that the crystalline size has been decreased with cerium doping. From the optical studies, the average transmittance of both the films exhibited more than 90 % transparency in visible region (400–700 nm). Moreover, the optical band gap of Ce doped ZnO thin films increases from 3.235 to 3.278 eV. Field emission scanning electron microscopy study reveals uniform granular structure of the prepared samples. Mighty peak observed at 398 nm got broadened and less intense due to cerium doping and other shoulder peaks almost vanished as investigated from photoluminescence spectra.