Buffer-enhanced room-temperature growth and characterization of epitaxial ZnO thin films

The room-temperature epitaxial growth of ZnO thin films on NiO buffered sapphire (0001) substrate was achieved by using the laser molecular-beam-epitaxy method. The obtained ZnO films had the ultrasmooth surface reflecting the nanostepped structure of the sapphire substrate. The crystal structure at the surface was investigated in situ by means of coaxial impact-collision ion scattering spectroscopy. It was proved that the buffer-enhanced epitaxial ZnO thin films grown at room temperature had + c polarity, while the polarity of high-temperature grown ZnO thin films on the sapphire was − c . Photoluminescence spectra at room temperature were measured for the epitaxial ZnO films, showing only the strong ultraviolet emission near 380 nm .