Vertically aligned ZnO nanowires have been synthesized on Si substrate by catalyst-free thermal evaporating metallic zinc powder at a low temperature of 600 degreesC. Studies found that the ZnO nanowires are single-crystalline wurtzite structures with 70 nm in diameter and 10 pm in length. The turn on field of the ZnO nanowires was about 6.2 V/mum at a current density of 0.1 muA/cm(2), and the emission current density reached 1 mA/cm(2) at an applied field of about 15.0 V/mum. Field emission property from the ZnO nanowires was enough high level to be applicable to field emission displays and vacuum microelectronic devices. (C) 2005 Elsevier B.V. All rights reserved.