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O: Fachverband Oberflächenphysik
O 84: Electronic Structure of Surfaces I: Spectroscopy, Surface States
O 84.2: Talk
Thursday, March 21, 2024, 10:45–11:00, MA 144
Recent progress in ToF-XPEEM and Momentum Microscopy: Theory and Experiment — •O. Tkach1,2, Q. Nguyen3, O. Fedchenko1, S. Chernov4, D. Kutnyakhov4, F. Pressacco4, J. Dilling4,5, L. Bruckmeier4,5, F. Scholz4, M. Scholz4, M. Hoesch4, K. Rossnagel4,5, H.-J. Elmers1, and G. Schönhense1 — 1Univ., Mainz — 2SumDU, Ukraine — 3SLAC Nat. Accel. Lab., USA — 4DESY, Hamburg — 5CAU Kiel
Cathode-lens instruments (PEEM, LEEM, momentum microscopes MM) usually have a strong accelerating electric field in front of the sample. Here we present an alternative route towards good performance in k-imaging mode. It is based on *field shaping* in the region close to the sample by planar concentric ring electrodes. Ray-tracing reveals: (i) An accelerating lens in front of the sample reduces spherical aberration and field curvature, enabling large k-fields of view. (ii) A retarding lens can tune the field to zero, enabling studies of non-planar objects in zero field. (iii) Stronger retarding fields direct all slow electrons back to the surface, reducing space-charge effects in pump-probe experiments. Simulations are confirmed by first experiments at PETRA-III and FLASH.
Keywords: Momentum Microscopy; ToF-XPEEM; Space-charge effects