High density of ZnO nanowires is grown over zinc foil by a catalyst-free thermal evaporation process. Electron microscopy studies confirmed that the as-grown nanowires are hexagonal wurtzite structure. The nanowires diameter was similar to 50nm with typical length of the order of mu m. Photoluminescence (PL) spectrum of the wires consist of a strong blue emission peak at 2.54eV accompanied by other peaks of relatively lower intensities. The Raman spectra of the ZnO nanowires exhibit compressive stress due to the local heating effects during the synthesis. The field emission measurement indicated that ZnO nanowires have a turn-on field of 13.5V/mu m at current density of 0.001 mu A/cm(2).