Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 78: Electronic Structure of Surfaces I: Photoelectron Spectroscopy

O 78.4: Vortrag

Donnerstag, 4. April 2019, 11:30–11:45, H14

Breakthrough in HAXPES Performance Combining Full-Field k-Imaging with Time-of-Flight Recording — •K. Medjanik¹, S. Babenkov¹, D. Vasilyev¹, S. Chernov¹, O. Fedchenko¹, B. Schönhense², C. Schlueter³, A. Gloskowskii³, Yu. Matveyev³, W. Drube³, H.J. Elmers¹, and G. Schönhense¹ — ¹JGU, Inst. für Physik, Mainz — ²Imperial College, London — ³DESY, Hamburg

In order to overcome the intensity/resolution problem of hard X-ray angular-resolved photoelectron spectroscopy (HARPES), we have developed a k-microscope with a modified lens system optimized for high kinetic energies (>7 keV) and very large field of view in k-space (up to 20 Å⁻¹ diameter) [1]. First results with this instrument have been taken at the new beamline P22 at PETRA III (Hamburg) [2]. The high X-ray brilliance (1.1x10¹³ hν/s in a spot of < 20x15 µm²) allows mapping of the 3D bulk Brillouin zone in a few hours. We found that the concept of tomographic k-space mapping previously demonstrated in the soft X-ray regime [3] works equally well in the hard X-ray range. Sharp valence band k-patterns of Re collected at an excitation energy of 6 keV correspond to direct transitions to the 28^th repeated Brillouin zone. X-ray photoelectron diffraction (XPD) patterns with < 0.1^∘ resolution are recorded within minutes. The high count rates pave the way towards spin-resolved HAXPES using an imaging spin filter.

[1] K. Medjanik et al., arXiv:1810.11366 (2018); [2] C. Schlueter et al., Synchr. Radiation News 31, 29 (2018); [3] K. Medjanik et al., Nature Materials 16, 615 (2017).