Structural and optical properties of single-crystalline ultraviolet-emitting needle-shaped ZnO nanowires

Well-crystallized with excellent optical properties, needle-shaped ZnO nanowires have been synthesized on silicon substrate in a high density via the thermal evaporation of metallic zinc powder without the use of catalysts or additives. Extensive structural analysis showed that the grown nanowires are highly crystalline with the wurtzite hexagonal phase, grown along the [0001] in the c-axis direction. The presence of an optical-phonon E2 mode in Raman spectrum at 437 cm− 1 and sharp and strong UV emission at 379 nm with no green emission in the room-temperature photoluminescence (PL) spectrum confirms good crystallinity with the excellent optical properties for the deposited nanowires.