Some new directions in materials and nanostructure studies with photoemission: standing waves and hard x-rays
Prof. Dr. C. Fadley (Dept. of Physics, UC Davis, zurzeit Forschungszentrum Jülich)

I will discuss several recent developments in studies of magnetic nanostructures, complex materials, and buried interfaces using synchrotron-radiation-excited photoemission, with special emphasis on work in the soft x-ray regime at the Berkeley Advanced Light Source, but consideration also of some emerging hard x-ray experiments. Instrumentation that has been developed to carrying out multiple soft x-ray spectroscopies with varying degrees of surface sensitivity (photoemission, x-ray absorption, and x-ray emission/inelastic scattering) on a single sample will be introduced, together with future prospects for photoemission making use of much higher-speed detection. Then a new standing wave-wedge method for non-destructively studying buried interfaces in multilayer nanostructures will be considered. This method has to date permitted determining concentration and magnetization profiles through an Fe/Cr giant magnetoresistive interface, as well as layer-specific densities of states in a magnetic tunnel junction consisting of FeCoB/FeCo/Al₂O₃. This approach should also be useful in a variety of other interface studies, e.g. of liquid-solid interfaces. Application of the multi-spectroscopy experimental system to the colossal magnetoresistive oxide materials La_1-xSr_xMnO₃ (x = 0.3, 0.4) will also be discussed. Finally, throughout the talk, the relatively new field of photoemission with excitation energies in the 5-15 keV range will be considered, including the possibility of band structure mapping or densities of states measurements with more bulk sensitivity.