Invited Paper SA+AS-MoA1
Photoemission with Soft and Hard X-Rays: Past, Present, and Future

Monday, November 7, 2016, 1:40 pm, Room 103C

In this talk, I will begin by briefly reviewing some of the key early developments in soft x-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS), x-ray photoelectron diffraction (XPD), and soft x-ray angle-resolved photoemission (ARPES). I will then consider combining these well-established methods with more recent techniques involving the tailoring of the x-ray wavefield through standing-wave (SW) excitation or total-reflection (TRXPS) to provide enhanced depth resolution and the use of hard x-ray excitation in the multi-keV regime (HXPS, HAXPES) to study bulk materials and buried layers and interfaces [1-5]. Applications to semiconductor- [1], oxide- [2.4,5], and magnetic- [2] heterostructures, as well as liquid/solid interfaces [3] will be considered. Future possibilities combining these approaches with variable polarization, as well as spin-, space-, and time- resolution will also be discussed.

Acknowledgements:

This work was supported by the U.S. Department of Energy, Contracts DE-AC02-05CH11231 at LBNL and DE-SC0014697 at UC Davis, and through the LDRD Program of LBNL.

References:

[1] “Bulk Electronic Structure of the Dilute Near-Ferromagnetic Semiconductor Ga_1-xMn_xAs via Hard X-Ray Angle-Resolved Photoemission” A. X. Gray, J. Minar, S. Ueda, P. R. Stone, Y. Yamashita, J. Fujii, J. Braun, L. Plucinski, C. M. Schneider, G. Panaccione, H. Ebert, O. D. Dubon, K. Kobayashi, and C. S. Fadley, Nature Materials 11, 957 (2012).

[2] “Interface properties of magnetic tunnel junction La_0.7Sr_0.3MnO₃/SrTiO₃ superlattices studied by standing-wave excited photoemission spectroscopy”, A. X. Gray et al., Phys. Rev. B 82, 205116 (2010);“Momentum-resolved electronic structure at a buried interface from soft X-ray standing-wave angle-resolved photoemission”,A.X. Gray et al., Europhysics Letters 104, 17004 (2013).

[3] “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., Nature Communications 5, 5441 (2014).

[4] “Depth profiling charge accumulation from a ferroelectric into a doped Mott insulator”,M. Marinova, J. E. Rault, et al., Nano Letters 15, 2533−2541 (2015).

[5] “Energetic, spatial and momentum character of a two-dimensional electron gas at the buried interface between GdTiO₃ and SrTiO₃”, S. Nemšák et al., Phys. Rev. B, to appear, http://arxiv.org/abs/1508.01832 .