ANGLE-RESOLVED XPS STUDY OF INHOMOGENEOUS SPECIMENS OF POLYCRYSTALLINE SILVER COVERED WITH UNIFORM GRAPHITE OVERLAYERS

The depth dependence of the XPS peak shape parameter is determined exp erimentally for inhomogeneous specimens of the type f(x) = 0 for x(o) > x > 0 and f(x) = constant for x > x(o), where f(x) is the electron e mitter concentration as a function of depth (x) and x, is the overlaye r thickness. In order to do this, specimens with sharp interfaces are prepared by depositing uniform overlayers of graphite on flat surfaces of polycrystalline silver. The peak shape parameter thus determined i s found to be a function of the overlayer thickness. The observed depe ndence has been explained in terms of the existing first order analyti cal expression for this parameter. Angle resolved studies have also be en done to explore the possible contributions arising out of surface e xcitation losses. Such studies clearly pointed out the presence of suc h an effect. Experimental results are discussed with a special emphasi s on the possible sources of systematic errors which may contribute to the measured values of this parameter.