Room-temperature epitaxial growth and in situ CAICISS surface analysis of wurtzite-type thin films

Low-temperature epitaxial growth of wurtzite-type thin films of ZnO and AlN was examined by laser molecular beam epitaxy (laser MBE), and the surface structure of these films was analyzed by in situ coaxial impact-collision ion scattering spectroscopy (CAICISS). We have achieved room-temperature (∼20 °C) epitaxial growths of ZnO films on NiO- or AlN-buffered sapphire(0 0 0 1) substrates as well as AlN films on TiN-buffered sapphire(0 0 0 1) substrates, while the ZnO films or AlN films were grown in the polycrystalline or amorphous phase on sapphire(0 0 0 1) without any buffer layers at room temperature. From in situ CAICISS measurements, the deposited ZnO films were found to have +c polarity, that is, Zn-plane termination on the NiO- or AlN-buffered sapphire at room temperature. These room-temperature epitaxially grown films had the ultra-smooth surface, exhibiting atomic steps derived from the substrate.