Temperature-enhanced ultraviolet emission in ZnO thin film

Abstract: We have studied the structural and optical properties of ZnO thin films prepared by thermal oxidation of ZnS films deposited by plasma assisted electron-beam evaporation on Si(100) substrates. The transformation from zinc blende ZnS to hexagonal wurtzite ZnO is confirmed by Raman and X-ray diffraction (XRD) measurement. For the sample thermally oxidized at 600°C for 2h, a novel UV emission peak Ix located at 3.22eV (385nm) has been observed. The temperature-dependent photoluminescence spectra show that the integrated intensity of Ix increases exponentially with increasing temperatures within the measuring temperature range, from 80 to 300K, but the peak position remains nearly constant. We explain this behavior in terms of electron tunneling into the radiative recombination centers. [Copyright &y& Elsevier]