Dresden 2020 – wissenschaftliches Programm
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MM 42.4: Vortrag
Mittwoch, 18. März 2020, 16:30–16:45, IFW D
Electronic structure and core electron fingerprints of caesium-based antimonides for ultra-bright electron sources — Caterina Cocchi1,2, Sonal Mistry3, Martin Schmeisser3, •Raymond Amador1,2, Julius Kuehn3, and Thorsten Kamps1,3 — 1Humboldt-Universität zu Berlin, Institut für Physik, 12489 Berlin, DE — 2Humboldt-Universität zu Berlin, IRIS Adlershof, 12489 Berlin, DE — 3Helmholz-Zentrum Berlin, 12489 Berlin, DE
The development of novel photocathode materials for ultra-bright electron sources demands understanding of intrinsic material properties, given constraints of growth and operational conditions. In a joint ab initio and experimental work, we propose a method to relate computed and measured core-level shifts and quantum efficiency of three alkali antimonides, which are particularly appealing for their absorption in the visible region. In our density-functional theory calculations we focus on Cs3Sb, Cs2KSb, and CsK2Sb. Experimentally, Cs-K-Sb samples with different stoichiometries and relative elemental content are investigated using x-ray photoemission spectroscopy (XPS). The largest core-level shifts (2 eV and 0.5 eV for K 2p and Sb 3d, respectively) can be correlated to XPS survey spectra, where such peaks are clearly visible. Core-level shifts can thus be used to identify specific compositions of Cs-K-Sb materials and their relation to measured values of quantum efficiency. Our results represent the first step towards a robust connection between the experimental preparation and characterisation of photocathodes, the ab initio prediction of their electronic structure, and the modeling of emission and beam formation processes.