Structural and optical properties of ZnO thin films deposited by sol–gel method: effect of stabilizer concentration

Nanocrystalline thin films of ZnO were successfully deposited on Si substrate via sol–gel method using zinc acetate dehydrate as a precursor and 2-methoxy ethanol as a solvent. The effect of stabilizer concentration on the structural and optical properties of the ZnO thin film was investigated as the stabilizer concentration affects the growth orientation of ZnO thin films prepared by sol–gel method. The growth in (002) plane of hexagonal structure is preferred in many applications as the 2-dimensional Zn atoms population is highest in this orientation. The growth of (002)-oriented ZnO films was optimized with the concentration of the stabilizer (triethanolamine). The crystal structures of the samples were analyzed using X-ray diffractometer confirming the polycrystalline nature and hexagonal structure of films. In order to estimate the preferential crystallite orientation quantitatively, the texture coefficient (T_c) was calculated. The particle size and strain was also found to change with concentration of stabilizer. SEM results confirm the formation of nanocrystalline thin films with homogeneous morphology. Photoluminescence characteristics show a direct band gap transition which shifts towards lower wavelength with increase in stabilizer concentration. It was observed that the stabilizer concentration is the most important factor to grow a highly (002)-oriented ZnO film along c-axis.