Invited Paper AS-MoA7
Looking Beneath the Surface: Electron Spectroscopy with X-ray Standing Waves and Hard X-rays

Monday, October 20, 2008, 4:00 pm, Room 207

I will discuss two relatively new developments in photoemission: the use of nanometer-scale standing-wave (SW) excitation so as to selectively look at different depths below the surface^1-3 and the use of harder x-ray excitation in the multi-keV range so as to probe more deeply below the surface, in what has been termed HAXPES or HXPS.⁴ Both of these approaches have the potential for enhancing the sensitivity of photoemission to both bulk and buried interface properties, while at the same time permitting the study of near-surface phenomena. After a brief overview of basic concepts, I will discuss several recent applications of these methods, separately and in concert. These will include: variable-temperature HXPS measurements at the ESRF on fractured cubic and cleaved bilayer lanthanum strontium manganite samples,^5,6 SW HXPS measurements at both BESSY⁷ and SPring8⁸ on systems of relevance to spintronic and semiconductor IC applications, the possibility of doing angle-resolved HXPS so as to carry out band mapping,⁹ and the possible benefits of photoelectron diffraction in the hard x-ray regime for local structure determinations.¹⁰

Work supported by the U.S. Dept. of Energy under Contract No. DE-AC03-76SF00098, and by the Helmholtz Association and the Humboldt Foundation.
¹S.-H. Yang, B.S. Mun et al., J. Phys. Cond. Matt. 14, L406 (2002).
²S.-H. Yang, B.S. Mun, and C.S. Fadley, Synchrotron Radiation News 17 (3), 24 (2004).
³S.-H. Yang, B. S. Mun et al., J. Phys.: Condens. Matter 18, L259–L267 (2006).
⁴C. S. Fadley, Nucl. Inst. and Meth. A 547, 24-41 (2005), and other papers in this special journal issue edited by J. Zegenhagen and C. Kunz.
⁵F. Offi et al., Phys. Rev. B 75, 014422 (2007).
⁶F. Offi, N. Mannella et al., Phys. Rev. B, in press.
⁷F. Kronast, S. Döring, M. Gorgoi, R. Ovsyannikov, A. Kaiser, C. Wiemann, S.-H. Yang, M. Huijben, A. Locatelli, D. E. Bürgler, R. Schreiber, F. Schäfers, W. Braun, H.A. Dűrr, C. M. Schneider, C. Westphal, C. S. Fadley, BESSY Highlight 2007, and to be published.
⁸C. Papp, B. Balke, et al., to be published.
⁹L. Plucinski, J. Minár, et al., Phys. Rev. B, submitted.
¹⁰A. Winkelman and C.S. Fadley, to be published.