A field ion microscopy study of nickel oxide

In-situ oxidation of nickel surfaces was investigated by field ion microscopy (FIM). Good quality images of nickel oxide were obtained with a Ne imaging gas. Individual atomic planes were observed on low index planes, even though the resolution of the image was not as good as that of the Ni substrate. It was found that the oxide was formed on the nickel substrate with a cube/cube relationship. An interesting observation is that the (100) planes of the nickel oxide display a unique square structure, while the (111) planes display normal circular concentric rings. The concentric rings of the oxide and metal phases were continuous at the oxide/metal interface. From the continuity of the planes through the interface, it is concluded that the oxide phase has grown epitaxially from the substrate with a sharp interface.