The Structure of Thin Oxide Films Formed on Nickel Crystals

Abstract

A study was made of the structural details of thin oxide films formed on the (100), (111), (110), and (311) of nickel. Oxidation temperatures ranged from 400° to 600°C, and the oxide films produced were between 25 and 500Aå thick. An x‐ray technique was utilized to measure the average strain in the films, the mosaic spread, the thickness, and the epitaxial relationships between oxide and metal. The oxide films on all crystal planes studied were observed to contain large numbers of short circuit diffusion paths. A change in the extent of these diffusion paths in the oxide on a given crystal plane produced a corresponding change in the oxidation rate. Furthermore, there was a variation in the extent and efficiency of the short circuit diffusion paths as a function of crystallographic orientation of the substrate, and this variation correlated directly with the marked oxidation rate anisotropy exhibited by nickel.