In addition to XPS, LEIS measurements were conducted, which exhibit an even greater surface sensitivity. Briefly, the measurement principle of LEIS is the scattering of noble gas ions from the sample surface. As these measured low energy ions show nearly no penetration into the sample material, the obtained information concerns exclusively the outer most atomic surface layer. In Fig. , the distribution of the elements with increasing sputter ion dose is shown (depth profile). The individual element intensities are normalized to the total intensity for each measurement. The total thickness removed by sputtering is between 20 and 30 nm, depending on the sample morphology.