Effect of thickness on structure and optical properties of Zn0.9Co0.1Oδ thin films deposited by magnetron sputtering in oxygen gas environment

Zn0.9Co0.1Od thin films have been deposited by radio frequency magnetron sputtering onto fused quartz
substrates under oxygen gas environments as a function of film thickness (time duration). The as deposited films show hexagonal wurtzite structure of ZnO with films orientated in (0 0 2) plane perpendicular to base plane, without any secondary phases of CoO in host ZnO matrix. The crystallite (D) values
estimated from XRD plots show increases with film thickness. The microstructural images recorded with field emission scanning electron microscopy (FE-SEM) have dense microstructure with an average grain size varies about 28–43 nm. The elemental composition of thin films were examined by energy dispersive spectroscopy confirms presence of Co in ZnO. The films have optical transmission in the visible region
is about 55–70%, the absorption edge shifts towards low energy range with increase in film thickness. The estimated optical energy band gap of as deposited films shows a decreasing trend as a function of film thickness. The optical energy band gap for all the films are listed is varies about 3.42–2.85 eV respectively.
2019 Elsevier Ltd. All rights reserved.