Electron channelling induced effects in grain boundary AES measurements

The influence of incident electron beam angle on the Auger peak height and peak height ratios was studied for clean and surface enriched iron single crystal samples and for grain boundary segregation on polycrystalline samples. The AES measurements were supplemented by observing electron channelling patterns (ECP) for the same samples within a SEM. Auger electron peaks for segregated species A seg are normalized with respect to the iron substrate Auger peak, A Fe , at 651 eV. A considerable change of the Auger peak height ratio A seg / A Fe was observed for surface segregation single crystal planes depending on the incident electron beam angle. The main contribution of the observed changes comes from variations of the iron substrate Auger peak A Fe and is attributed to electron channelling effects. The same is true for AES measurements on grain boundaries of polycrystalline samples, if the incident electron beam is nearly parallel to a low index crystallographic pole. Some recommendations are given for performing quantitative AES measurements on grain boundary surfaces.