Single-crystalline wurtzite GaN nanowires have been synthesized through ammoniating Ga2O3/Ta films by RF magnetron sputtering. The products have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron microscopy (XPS) and photoluminescence (PL). The results show that the nanowires have a hexagonal wurtzite structure with diameters ranging from 10 nm to 30 nm and lengths typically up to several tens of micrometers. The representative photoluminesccnce spectrum at room temperature exhibits a strong UV light emission band centered at 364 nm. The growth mechanism of the crystalline GaN nanowires is discussed briefly. (C) 2007 Elsevier B.V. All rights reserved.