Influence of ion mixing on the depth resolution of sputter depth profiling

During sputter depth profiling, the bombarding ions for sputtering also produce ion mixing at interfaces. As a result, ion bombardment changes the original composition profile of the specimen, setting a limit on the depth resolution of the sputter depth profiling technique. The origin and magnitude of the effect of ion mixing on the depth resolution of sputter depth profiling have been studied using x-ray photoelectron spectroscopy, Auger electron spectroscopy, and Ar+sputter depth profiling of Pt/Zr, Pt/Mo, Pt/Ti, and Pt/Ni interfaces. It is shown that the effect of ion mixing is an intrinsic limitation on the depth resolution; it depends on the thermodynamic properties, such as the heat of mixing and the cohesive energy, of the solids under examination. The magnitude of the effect of ion mixing is compared with that of the instrument-dependent limitations on the depth resolution of sputter depth profiling.