Probing multicomponent materials by Auger-electron-spec-trometry

Abstract

In quantitative Auger electron spectroscopy (AES) analysis, the emphasis is generally laid on the vertical variation in signal from an element versus the variation in composition from the surface to the bulk. In such a framework, a quantitative method has been previously developed by the authors, which provides such information as the thickness of a segregated layer or the initial growth process of a thin film. Here, this method is applied to study a horizontal variation of composition, i.e. the signal variation of a scanning Auger electron microscope (SAM) when the incident electron beam is scanned across the boundary of grains of different composition. In order to evaluate the SAM resolution, for the case of an ideal step boundary, calculations are carried out by taking into account the influence of angular distributions, of attenuation length of primary, secondary and Auger electrons, of secondary electron yield and of the beam shape (point, Gaussian or columnar). The results for the cases of Ag-Au, Si-Ag and Be-Cu, lead to a SAM spatial resolution of ≈30 Å for a primary beam of 2–3 keV with an infinitesimal diameter and a resolution of the order of the beam size for Gaussian and columnar beams. Extrapolation of this method to a primary beam energy of 20 keV is discussed and leads to results similar to those obtained by Monte Carlo simulation.