Strong enhancement of ultraviolet emission from ZnO films by V implantation

ZnOfilms were prepared on Si(100) wafers by rf sputtering and subsequently implanted with V ions to fluences of (1,2.5,5,10)×10¹⁵ cm¯². The room-temperature ultraviolet photoluminescence(PL) intensity of the implantedfilms is shown to increase with increasing fluence up to 2.5×1015 cm−2, becoming ∼37 times more intense than the emission from the unimplanted ZnOfilm, before decreasing at higher fluences. The increase in PL intensity is correlated with improved crystallinity of ZnO, accompanied by a reduction in the concentration of deep-level native defects by V incorporation into the ZnO lattice, as verified by x-ray diffraction, x-ray photoelectron spectroscopy, and low-temperature PL. The subsequent reduction in PL intensity at fluences higher than 2.5×10¹⁵ cm¯² is shown to result from the deterioration of the crystal quality and the precipitation of V secondary phase possibly introducing defects in the films