High-resolution hard-x-ray photoelectron diffraction in a momentum microscope—the model case of graphite

New journal of physics 21(11), 113031 - (2019). doi:10.1088/1367-2630/ab51fe
Hard x-ray photoelectron diffraction (hXPD) patterns recorded with a momentum microscope withhigh k-resolution (0.025 Å−1 equivalent to an angular resolution of 0.034° at 7 keV) revealunprecedented rich fine structure.Wehave studied hXPD of theC1s core level in the prototypicallow-Z material Graphite at 20 photon energies between 2.8 and 7.3 keV. Sharp bright and dark linesshift with energy; regions of Kikuchi band crossings near zone axis exhibit a filigree structure whichvaries rapidly with energy. Calculations based on the Bloch wave approach to electron diffraction fromlattice planes show excellent agreement with the experimental results throughout the entire energyrange. The main Kikuchi bands in the [001] zone axis appear fixed on the momentum scale with awidth of the corresponding reciprocal lattice vector, allowing to reconstruct the size of the projectedBrillouin zone. The newly developed high-energy k-microscope allows full-field imaging of(kx, ky)-distributions in large k-fields (up to>22 Å−1 dia.) and time-of-flight energy recording.
Published by IOP, [London]