A novel Monte-Carlo based method for quantitative thin film X-ray microanalysis

A novel approach to the quantitative analysis of thinned samples, which exploits the finite and variable width of the incident beam of an analytical electron microscope (AEM), is reported. For a binary alloy AB, the method requires two measurements of the I(AK alpha)/l(BK alpha) X-ray intensity ratios, obtained with two different beam diameters. The digital image of the beam is also recorded by a slow-scan CCD camera; its pixel intensities are converted into probability densities by our Monte Carlo code, which has been modified to simulate the electron trajectories crossing the vertical boundaries of the sample. The result of the simulation consists of two thickness t vs concentration C matrices for the two different spot sizes; the unique t-C combination, corresponding to the analyzed region, is obtained through the convergence routine described in our previous papers, This method has been applied to the analysis of Si-Ge alloys in AEM cross sections of Si/Si1-xGex/Si heterostructures. The Ge concentrations obtained by this method on samples of different composition and thickness are in agreement with those deduced from other experimental techniques.