Chemical state resolved depth-profiling using XPS and the maximum entropy method

Harries, J.; Tode, Mayumi; Inoue, Keisuke; Sumimoto, Yuichi; Yoshigoe, Akitaka ; Teraoka, Yuden

There are many available methods for determining the elemental distributions within a sample in the depth direction, but angle-resolved X-ray photoelectron spectroscopy offers the advantage of chemica-state specificity. At the surface chemistry station at BL23SU, SPring-8, we have recorded depth-profiles for thin films generated using supersonic molecular beams and ion beams. To extract the depth-direction information from the angular resolved spectra we use the maximum entropy method. We explain the techniques, and present the specific example of the natural oxide of VCrTi, a hydrogen storage material. Also, we investigate the thermal stability of the oxide by generating depth profiles during annealing of the sample.