Regensburg 2019 – wissenschaftliches Programm
KFM 5: Instrumentation for Micro-/Nano-Analysis and Lithography/Structuring (joint session KFM/DS/O)
KFM 5.3: Vortrag
Montag, 1. April 2019, 15:50–16:10, PHY 5.0.21
Hard X-ray Photoelectron Diffraction in Graphite — •Olena Fedchenko1, Sergey Chernov1, Katerina Medjanik1, Sergey Babenkov1, Dmitry Vasilyev1, Aimo Winkelmann2, Hans-Joachim Elmers1, and Gerd Schönhense1 — 1JGU, Institut für Physik, Mainz — 2Laser Zentrum, Hannover
A new high-energy momentum microscope (kinetic energies up to >7 keV) allows full-field imaging of the (kx-ky) photoelectron distribution with a large field of view (up to 20 Å−1 dia.) in momentum space and ToF energy recording. Avoiding symmetry-varying rotation of sample and/or analyser, "full-field k-imaging" provides an ideal means for X-ray photoelectron diffraction (XPD) studies. High-resolution (< 0.1∘) diffractograms can be recorded within minutes thanks to the high brilliance of beamline P22 at PETRA III . We present an XPD study for electrons from the C 1s core level in graphite in a wide energy range from 2840 to 7283 eV. Fine details in the diffractograms reflect the large number of scatterers (105-106) due to the large inelastic mean free path. A calculation based on the Bloch wave approach to electron diffraction by lattice planes  shows excellent agreement. The short photoelectron wavelength (10% of the interatomic distance) "amplifies" phase differences and turns hard X-ray XPD into a very sensitive structural tool. The results are important for valence band XPD .
 C. Schlueter et al., Synchr. Radiation News 31, 29 (2018);  A. Winkelmann et al., New J. of Phys. 10, 113002 (2008);  G. Schönhense et al., arXiv 1806.05871 (2018).