Spectroscopy of zinc oxide thin films near the fundamental absorption edge

The optical absorption spectra of zinc oxide (ZnO) thin films formed by reactive cathode sputtering are studied. The observed absorption of light in the region of photon energies lower than the band gap is explained by the presence of tails of localized states in the band gap. The band gap width and the characteristic Urbach energy are determined. The influence of the structural specific features and the impurity factor on the behavior of the experimental spectral dependences is determined.