Abstract
The aim of this work was to carry out systematic studies of how synthesis temperatures affect the morphology and properties of mixed zinc sulfide/zinc oxide (ZnSxOy and ZnO) nanostructures, and to get reliable data on optical constants of ZnSxOy and ZnO nanowires/nanobelts (NW/NB) for the use in device applications. ZnSxOy and ZnO NWs/NBs were fabricated using vapor transport in an open-end tube. Mixed ZnS(0.47)O(0.62)NWs was obtained at the synthesis temperature of 850 degrees C. The sulfur content disappeared as the temperature increased to 950 degrees C and 1050 degrees C and the morphology changed to a mixture of NW/NB. The NW prepared at 850 degrees C were indexed as mixed phases of hexagonal ZnS and hexagonal ZnO structures. The NW/NB prepared at 950 degrees C and 1050 degrees C were indexed as pure hexagonal ZnO structures. The thickness, surface roughness, and optical constants of the synthesized nanostructured samples were extracted from measurements of spectroscopic ellipsometry. A two-layers model was proposed to fit the calculated data to the measured ellipsometric spectra. The estimated band gap values of the prepared nanostructures lay 0.66-0.79 eV below the bulk ZnO value due to the lower oxygen content present in the samples and the stresses built in the samples during preparation.