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.