Quantitative analysis of mixed (Mo,W) carbides by means of least-squares minimization performed on auger spectra simulations

Surface analysis was performed by Auger spectroscopy on mixed (Mo,W) carbid es that were synthesized with a 50:50 molar ratio of both metals. Because o f the molybdenum and tungsten Auger peak overlap in the energy window betwe en 100 and 230 eV, a linear combination of appropriately chosen standard sp ectra was requested in order to determine their composition quantitatively. Therefore, molybdenum, tungsten and mixed (Mo,W) carbides were prepared an d characterized by electron and x-ray diffractions. The diffraction techniq ues allowed the determination of the carbide phases corresponding to specif ic metal/carbon stoichiometries. The Auger spectra of mixed (Mo,W) carbides were simulated by weighted sums of the Auger spectra of alpha-WC and MoC. A least-squares method was applied on the simulated Auger spectra, in the w hole energy window, in order to determine the best simulation revealing the true composition of the mixed (Mo,W) carbides. This technique requires the homogeneity of the sample over a larger depth than the inelastic mean free path of the Auger electrons. Moreover, it allowed the determination of dif ferent compositions of mixed (Mo,W) carbides resulting from different prepa ration routes. (C) 1999 John Wiley & Sons, Ltd.