Quantitative non‐destructive in‐depth composition information from XPS

The XPS peak shape from inhomogeneous transition metals is studied theoretically under variation of the path length R travelled by the photoelectron in the solid, the XPS peak energy E p , and the particular metal M . The variation in peak shape is characterized by a single parameter D = A p / B which is the ratio of the peak area to the increase in background signal 30 eV below the peak energy. It is found that D is a strong function of R , a moderate function of E p and to first order independent of M . This gives theoretical support to the idea suggested previously of using D for fast non‐destructive extraction of in‐depth composition information. To a good approximation we have D ( R,E p ) = (425+ E p ) × R , with E p in eV, R in Å and D ( R,E p ) in eV. The practical use of this function in the analysis of experimental data is discussed.