Influence of growth temperature, working gas ratio, and buffer layer in ZnO films grown on (001) Si substrates by using rf-sputtering

We report on an extensive research result about the relationship between the growth parameters of growth temperature, working gas ratio, and Low-temperature (LT) ZnO buffer and the physical properties of surface properties, structural properties, and optical properties in the ZnO films grown on (001) Si substrates by rf-sputtering. In the substrate temperature range of room temperature (RT) - 500 A degrees C, a higher temperature is found to lengthen the surface migration lengths of Zn and O atoms and to promote their surface reaction. In the O-2/Ar+O-2 ratio range of 0-80%, a higher O-2/Ar+O-2 ratio is found to suppress the generation of nonradiative recombination centers due to the nonstoichiometric point defects such as O vacancies and Zn interstitials. The buffer layers deposited at RT are found to be partially crystallized by annealing at a high temperature and to be able to serve as seeds for the following ZnO film growth. As a result, the ZnO films fabricated at a substrate temperature of 500 A degrees C and an O-2/Ar+O-2 ratio of 80% with a LT-ZnO buffer annealed under an O-2 ambient of 10 mTorr have the highest crystalline quality.