ALUMINUM DEPOSITION ON NIO(100) - GROWTH, STRUCTURE AND COMPOSITION OF THE INTERFACE

Ultra-thin films were grown on stoichiometric NiO(100) single crystal surfaces by depositing aluminum at 250-degrees-C. The aluminum interac ts very strongly with the NiO and an epitaxial Ni3Al(100) layer is for med at the interface. Reflection high energy electron diffraction (RHE ED) and atomic force microscopy (AFM) indicate that the film initially wets the NiO surface but quickly roughens with increasing film thickn ess. Photoemission (XPS and UPS) measurements show that the NiO substr ate becomes Ni-deficient as the metallic Ni3Al phase grows by extracti ng Ni from the underlying NiO. Above an average film thickness of 10 m onolayers, a polycrystalline aluminum layer forms on top of the Ni3Al phase when the Ni diffusion becomes rate limiting. Defects and non-sto ichiometry on the NiO(100) surface intentionally created prior to grow th affect the disorder and roughness of the growing film, but do not c hange the overall growth mechanism.