Passivation of defects in ZnO nanowires by SiO2 sputtering deposition

Passivation of native point defects in ZnO nanowires was successfully achieved by SiO2 deposition. The ZnO nanowires were grown on sapphire by the vapor-liquid-solid method and coated with SiO2 through reactive sputtering deposition. The samples were post-annealed at different temperatures in Argon atmosphere. Photoluminescence measurements at room temperature and electron transmission microscopy were performed. The coated nanowires present a core-shell structure. A strong oxygen vacancies passivation were observed resulting in a drastic suppression on visible light emissions in favor of UV ones. On the other hand, annealing at increasingly higher temperatures favored the oxygen desorption and the increase of deep-level states.