GaN nanowires have been successfully synthesized on Si(1 1 1) substrates by magnetron sputtering through ammoniating Ga2O3/Cr thin films at 950 degrees C. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR spectrophotometer, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), and photoluminescence (PL) spectrum were carried out to characterize the microstructure, morphology, and optical properties of GaN samples. The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure and high-quality crystalline, have the size of 30-80 nm in diameter and several tens of microns in length with good emission properties. The growth direction of GaN nanowires is perpendicular to the fringe of (1 0 1) plane. The growth mechanism of GaN nanowires is also discussed in detail. (C) 2010 Elsevier B. V. All rights reserved.