Room temperature ultraviolet emission from microcrystallite ZnO thin films

Strong room temperature ultraviolet emission is observed in highly oriented ZnO microcrystallite films prepared on (001) sapphire substrates by pulsed laser deposition method (PLD). The influences of substrate temperature, distance between the target and the substrate, oxygen pressure, and laser energy density on structural and optical properties were systemically studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and room temperature photoluminescence (PL) measurements. The XRD as well as the SEM results showed that all the four experiment parameters had obvious effects on the structure and micrograph of the derived ZnO films. From the room temperature photoluminescence spectra, all the derived samples have a strong ultraviolet (UV) emission about 376nm, and the visible emission is depressed greatly. Additionally, the results showed that the processing parameters could obviously affect the PL properties and the reasons were also discussed. From our results, the UV PL intensity is strongly depending both on the crystallinity and the stoichiometry of the ZnO films.