Measurement of oxygen transport in ceramics by SIMS

The most direct and accurate method of measuring the oxygen self diffusivity of oxide materials is isotope exchange followed by Secondary Ion Mass Spectrometry (SIMS) depth profiling. SIMS involves the bombardment of the sample in UHV by a high energy (keV) primary beam and then mass analysing the sputtered secondary ion nux. Isotopic fractions as a function of sputtered depth can be easily obtained from the raw data. The kinetic parameters describing the isotope exchange; k, the surface exchange coefficient, and D, the self diffusion coefficient, can be obtained by a non-linear least squares fitting of the depth profile data. The isotopic analysis of oxides by SIMS is explored, with particular reference to the fundamental Limitations governing this method of analysis, such as ion beam mixing and the development of surface topography during ion bombardment. The published kinetic data obtained by SIMS is then discussed. Finally the prospects for future development of the technique are mentioned including fine spot imaging instruments for the analysis of grain boundary phenomena in ceramics.