Morphological and optical investigation of Sol-Gel ZnO films

This paper presents morphological and optical studies of the properties of spin-coated ZnO films depending on the annealing temperatures. The films microstructure was explored using a scanning nano-hardness measuring device of the NanoScan family, based on the principles of atomic force microscopy, in a constant frequency mode. The surface study revealed that the root-mean-square (RMS) surface roughness of 985.64×985.64 nm ZnO films becomes greater with the increase of the annealing temperature, but the film surface remains uniform and smooth. The results were confirmed by XRD analysis, which demonstrated that the crystallite size grew from 25 to 36 nm with the thermal treatments. The ZnO films possessed high transmittance in the visible spectral range and the optical band gaps in ZnO films varied from 3.25 eV to 3.52 eV. The optical and morphological properties of the ZnO films formed on Si and quartz substrates are very good. The sol-gel approach proposed for deposition of nanostructured ZnO films is promising for applications in optoelectronic devices or solar cells. (paper)