SPECTROSCOPIC ELLIPSOMETRY OF NICKEL-OXIDE ZINC-OXIDE ARTIFICIAL SUPERLATTICES

Thin films of ZnO and NiO and their superlattices were made by an ion beam sputtering technique, The dielectric functions of these films wer e measured as a function of photon energy using a variable-angle spect roscopic ellipsometer, Artificial superlattices were formed in [(NiO)( 12)/(ZnO)(6)](10), [(NiO)(6)/(ZnO)(4)](16), and [(NiO)(7)/(ZnO)(8)](12 ) films, where ZnO had the rock salt structure rather than the wurtzit e type of structure, The dielectric functions of these superlattices w ere markedly different from those of pure ZnO, NiO, and their mixtures , However, ZnO had the wurtzite type of structure in [(NiO)(10)/(ZnO)( 20)](4). In this film, the epitaxial relation which enables the format ion of an artificial superlattice was not observed between ZnO and NiO layers, and the dielectric function could be interpreted as a simple mixture of ZnO and NiO.