Combined application of AES and XPS to study carbon diffusion through the selvedge of a Fe(100)-surface

Diffusion of carbon from an Fe(lOO) surface into the bulk, following halocarbon adsorption; is modelled using experimental data from AES and XPS experiments. The mean free path of C ZCLL Auger electrons (272 eV) in a dense monolayer of halogen atoms (Cl, Br) is found by a variety of experimental methods to be -3 A, a value substantially smaller than expected from tabulated data. As inferred from the combined information provided by the AES and XPS experiments, the concentration profile of carbon perpendicular to the surface follows a smooth distribution rather than a step function. The importance of accurate data for electron escape depths and of experimental detection limits for quantitative electron spectroscopy of a surface is indicated