I will present some new directions in synchrotron radiation soft x-ray photoemission (XPS, SXPS) and hard x-ray photoemission (HXPS, HAXPES, HIKE) [1-6], with illustrative examples of applications to a range of sample types. These involve combined SXPS and HXPS studies of buried layers and interfaces in magnetic and transition-metal oxide multilayers [1,2], as well as in semiconductor junctions [3]; solid-gas or solid-liquid interfaces with high ambient pressures [5]; band-offset measurements in multilayer structures [6]; and the use of standing waves from multilayer mirrors to enhance depth contrast in spectroscopy [1-5].
This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, the Army Research Office, under MURI Grant W911-NF-09-1-0398, the Forschungszentrum Julich, Peter Grunberg Institute, and the APTCOM project of Le Triangle de Physique, Paris.
1 “Determination of layer-resolved magnetic and electronic structure of Fe/MgO by standing-wave core- and valence- photoemission”, See-Hun Yang, Benjamin Balke, Christian Papp, Sven Döring, Ulf Berges, L. Plucinski, Carsten Westphal, Claus Schneider, Stuart S. P. Parkin, and Charles S. Fadley, Phys. Rev. B 84, 184410 (2011).
2 “Interface properties of magnetic tunnel junction La0.7Sr0.3MnO3/SrTiO3 superlattices studied by standing-wave excited photoemission spectroscopy”, A. X. Gray et al., Phys. Rev. B 82, 205116 (2010); and A.X. Gray et al., Europhysics Letters 104, 17004 (2013).
3 “Nondestructive characterization of a TiN metal gate: chemical and structural properties by means of standing-wave hard x-ray photoemission spectroscopy”, C. Papp, G. Conti, et al. J. Appl. Phys. 112, 114501 (2012).
4 “Hard X-ray Photoemission with Angular Resolution and Standing-Wave Excitation”, C. S. Fadley, invited review, J. Electron Spectrosc. 190, 165-179 (2013)
5 “Chemical-state resolved concentration profiles with sub-nm accuracy at solid/gas and solid/liquid interfaces using standing-wave ambient-pressure photoemission (SWAPPS)”, S. Nemsak et al., in preparation
6 “Band Offsets in Complex-Oxide Thin Films and Heterostructures of SrTiO3/LaNiO3 and SrTiO3/GdTiO3 by Soft and Hard X-ray Photoelectron Spectroscopy”, G. Conti, A. M. Kaiser, A. X. Gray, S. Nemšák , G. K. Pálsson, J. Son, P. Moetakef, A. Janotti, L. Bjaalie, C.S. Conlon D. Eiteneer, A.A. Greer, A. Keqi, A. Rattanachata, A.Y. Saw , A. Bostwick, W.C. Stolte, A. Gloskovskii, W. Drube, S. Ueda, M. Kobata, K. Kobayashi , C. G. Van de Walle, S. Stemmer, C. M. Schneider and C. S. Fadley, J. Appl. Phys. 113 143704 (2013).