Strong enhancement of ultraviolet emission from ZnO films by v implantation

ZnO films 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 implanted films 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 ZnO film, 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.