Enhancement of band gap of ZnO nanocrystalline films at a faster rate using Sr dopant

Abstract

A faster rate of band gap enhancement of ZnO nanocrystalline films using strontium dopant is reported for the first time. Hexagonal wurtzite Zn1−xSrxO films have been deposited by sol gel spin coating using zinc acetate. The optical band gap increases from 3.150 to 3.275 eV as the Sr concentration increases from x = 0 to x = 0.03 showing an enhancement of 3.96% which is substantially higher than those reported earlier using Mg or Ca dopants indicating the possibility of application in optoelectronics. Strong UV and comparatively weak defect related emission are observed in photoluminescence spectra of the films. The NBE emission at 3.10 eV for undoped ZnO thin film shows a blue shift of 53 meV as Sr dopant concentration increases to 3 at. %. Films are also characterized by FTIR, AFM, SEM and EDX. Distinct characteristic absorption for Zn-O stretching modes are present. Surface of Zn1−xSrxO polycrystalline thin films are significantly smooth and show pentagonal shaped grains which approach to uniform spherical grains throughout the surface with increase in dopant concentration. The crystallite size along (002) plane is less than 10 nm for all samples.