EPMA of surface oxide films

Electron probe microanalysis (WDS) is used to study oxide film thickness (1-1000 nm), oxide stoichiometry, impurities of oxygen (about 1 wt%) in materials covered by a surface oxide film, and multilayer oxide formation on alloys. Excellent sensitivity for the determination of O Ka intensities is provided by W/Si multilayer monochromators. Modelling of K ratio versus E sub 0 (electron energy) plots is demonstrated as an accurate and versatile procedure of data reduction. The precision of the results in respect of oxide film thickness and oxide stoichiometry is in the range of 5-20%, depending on the complexity of the problem, the range of E sub 0, the experimental precision of the k ratios, and the magnitude of the oxide film thickness.