Effects of doping concentration on the structural and the optical properties of Sol-gel-derived In-doped ZnO thin films grown on muscovite mica substrates

Abstract

In-doped ZnO (IZO) thin films were grown on muscovite mica substrates by using the sol-gel process. The structural and the optical properties of IZO thin films with different In concentrations (0, 1.5, 3, 4.5, 6, and 7.5 at.%) were investigated. All films had a granular structures with spherical nanosized crystallites, and the film’s thickness decreased gradually with increasing In concentration. However, noticeable cracks were observed in the films for In concentrations above 4.5 at.%. The deep-level (DL) emissions in the photoluminescence spectra were found to depend on the In concentration, with a marked decrease in the full width at half maximum of the near-band-edge emissions at relatively high In concentrations. The average transmittance of all films in the visible region was higher than 80%. Increasing the In concentration also led to a slight decrease in the optical band gap and to a significant increase in the Urbach energy.