A CONFIRMATION OF THE DOUBLE-EXPONENTIAL APPROXIMATION OF THE DEPTH DISTRIBUTION FUNCTION FOR AES XPS USING RECIPROCAL 2-STREAM METHODS

The depth distribution function (DDF) for Auger/XPS spectroscopy obtai ned in the two-stream approximation contains little useful information . This situation may be improved considerably by invoking the principl es of reciprocity and solving instead the reciprocal problem. Doing so produces an approximate DDF of the same two-exponential form as the a pproximate DDF obtained in the transport approximation lending further credence to this result. There are many forms of the two stream metho d. However, from the literature it is clear that the delta-Eddington v ersion gives the best combination of accuracy and simplicity for the r eciprocal problem. Two forms of the delta-Eddington version are compar ed to the DDF from the transport approximation, leading to the conclus ion that the three DDF's which include elastic scattering are remarkab ly close to one another and substantially different from the DDF used in standard quantitative procedures. Using these forms of the DDF shou ld allow quantitative Auger/XPS spectroscopy to include elastic scatte ring in a simple yet accurate way.