In this work, GaN nanowires were fabricated on Si substrates coated with NiCl2 thin films using chemical vapor deposition (CVD) method by evaporating Ga2O3 powder at 1100 degrees C in ammonia gas flow. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM) and photoluminescence (PL) spectrum are used to characterize the samples. The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure. The growth mechanism of GaN nanowires is also discussed. (C) 2009 Elsevier B. V. All rights reserved.