Non-destructive depth profile analysis using synchrotron radiation excited XPS

We have used synchrotron radiation as excitation source in an X-ray photoelectron spectroscopy (XPS) experiment to analyse surface-near element depth profiles non-dectructively. By tuning the photon energy one can vary the kinetic energy of the photoelectrons and in turn the information depth of the measurement. To quantify the sample geometry (e.g. layer thicknesses) model calculations similar as for angle-resolved XPS (ARXPS) measurements are necessary. We have successfully applied this technique to several samples. We will show how to calculate the relative intensities of the peaks, using photoionization cross sections and an experimentally determined analyzer transmission function and the procedure to quantify the geometry for a model sample: natively oxidized Ta covered by carbon contamination. At Sn-doped indium oxide samples we found a sub-monolayer of segregated Sn at the surface which was expected from previous investigations.