Nanocrystalline zinc oxide (nc-ZnO) thin films with c-axis orientation were deposited on Si (100) substrates at a temperature lower than 100 degrees C by plasma assisted pulsed laser deposition from metallic zinc. Oxygen plasma generated by electron cyclotron resonance (ECR) microwave discharge was used as a reactive and energetic source to assist reactive deposition and oriented growth of nc-ZnO thin films. Atomic force microscopy (AFM) observation revealed the smooth surface appearance of the deposited nc-ZnO films. Analysis from Raman scattering and Fourier-transform infrared spectroscopy (FTIR) demonstrated the wurtzite structure of the deposited films. Structural characterization from x-ray diffraction (XRD) analysis showed the film growth with c-axis orientation perpendicular to the substrate surface and the nanocrystalline formation with average c-axis-oriented crystallites of 12 nm. The deposited nc-ZnO films are optically transparent in the visible and near infrared regions and the optical band gap was determined to be 3.32 eV. (c) 2008 American Vacuum Society.