Berlin 2024 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 8: Ultrafast Phenomena I
HL 8.5: Vortrag
Montag, 18. März 2024, 16:00–16:15, EW 015
Polaron Formation Dynamics in BiOI Nanoplatelets Studied by Time-Resolved PEEM — •Matthias Franz Kestler1,2, Kyung Chul Woo2, Justin W. X. Lim2, Lucas M. Prins1, Jochen Feldmann1, and Zhi-Heng Loh2 — 1Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstr. 10, 80539 Munich, Germany — 2School of Chemistry, Chemical Engineering and Biotechnology, and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
BiOI is a nontoxic, stable and polar semiconductor, which shows high conversion efficiencies in photocatalytic water splitting. This is due to an ultrafast and effective charge separation also launching coherent phonons after short laser pulse excitation. The coupling of electronic excitations and phonons should also manifest itself in polaronic effects. To gain unambiguous experimental evidence for polaronic effects we have carried out time-resolved photoemission electron microscopy (TR-PEEM) experiments. This technique offers the unique possibility to learn about the dispersion E(k) of the conduction band (CB) and its occupation with electrons as a function of time after pulsed optical excitation. In order to interpret our data it is not sufficient to describe merely the temporal evolution of the electron distributions in a static CB. We observe that the dispersion of the CB changes itself in time. This is in particular monitored around the Gamma point of the CB. This combined temporal change in band-structure and electron distribution can be explained by the formation of a polaronic excitation.
Keywords: Polaron; PEEM; Polaron Formation; BiOI; Hot Carrier Cooling