Analytical Electron- and Atomic Force Microscopy Study of Multilayered Oxide Films Formedon Ce-DOPED Ni

Abstract

ABSTRACTOxide films up to 200 nm thick were grown at high temperatures on Ni substrates implantedwith 2x1016 Ce ions/cm2. The surface morphology, microstructure and microchemistry were examined by AFM and TEM/STEM techniques. It has been found that the oxide films are composed of three well defined sublayers, with essentially different microstructure and Ce concentration. The outer layer is composed of NiO and CeO2 nanocrystals with a size less than 5 nm. The same two phases are also present within the middle layer, although the NiO grains are much larger in comparison to nano-sized CeO2. In addition, Ce segregation along the NiO grain boundaries is detected in this layer. The inner layer is the thickest one and is composed of pure NiO grains. Oxide films having such a complex structure are characterized by a very low diffusion rate for both metal and oxygen ions. Oxygen isotope experiments revealed that the diffusion processes within the oxide film are controlled by the Ce-rich layers.