ZnO thin films were obtained by two-step oxidation processes of Zn films: heating up to 575 K for 1-2 h followed by heating at higher temperature (775 K) for 1 h. Zinc thin films (d=450 nm) were deposited by the quasiclosed volume technique under vacuum onto glass substrates maintained at room temperature. The investigation of film structure, performed by x-ray diffraction technique, corroborated with atomic force microscopy, confirmed that as-prepared zinc films are polycrystalline. The as-prepared ZnO films have a polycrystalline wurtzite (hexagonal) structure, with film crystallites preferentially oriented with (002) planes parallel to the substrate. Transmission and absorption spectra were recorded in the spectral domain from 300 to 1400 nm. The energy band gap for respective films determined from absorption spectra ranged between 3.02 and 3.06 eV. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3484243]