Photoactivity enhancement of zinc sulfide ceramics thin films through ultrathin buffering engineering

Zinc-sulfide (ZnS) thin films 200 nm-thick with various crystal features were fabricated using RF sputtering onto patterned sapphire substrates with and without ultrathin homo-ZnS and hetero-zinc oxide (ZnO) ultrathin buffer layers (approximately 45 nm in thickness). Microstructural analyses revealed that the crystalline ZnS thin films with a columnar grain feature were deposited on the various ultrathin buffer layers-coated substrates through RF sputtering. The surface morphology of the ZnS thin films became rough and the crystal defect density of the ZnS thin films increased when the ZnS thin films were grown on the buffer layers. Comparatively, the rugged and island-like ZnO buffer layer engendered the crystal growth of the ZnS thin film with a higher degree of structural disorder than that of the crystal growth on the ZnS buffer layer. An increased crystal defect number together with the highly rugged film surface of the ZnS thin film buffered with ultrathin ZnO layers efficiently enhanced the photoactivity of the 200 nm-thick ZnS thin film in this study.