Regensburg 2019 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Ultra-fast phenomena
HL 46.2: Talk
Friday, April 5, 2019, 09:45–10:00, H31
Transient birefringence and dichroism of ZnO studied by femtosecond time-resolved spectroscopic ellipsometry — •Oliver Herrfurth1, Steffen Richter2, Mateusz Rȩbarz2, Shirly Espinoza2, Joshua A. Leveillee3, André Schleife3, Jakob Andreasson2,4, Marius Grundmann1, and Rüdiger Schmidt-Grund1 — 1Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Leipzig — 2ELI Beamlines, Institute of Physics, Czech Academy of Science, Prague, Czech Republic — 3Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, USA — 4Condensed Matter Physics, Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
We report on UV-pump-induced transient birefringence and dichroism of an m-plane oriented ZnO thin film measured by femtosecond pump-probe spectroscopic ellipsometry in the spectral range from 340 nm to 690 nm (1.8 eV to 3.6 eV) with approximately 100 fs time-resolution. The pump-induced density of electron-hole pairs is estimated as 3×1019cm−3. We determine the complex dielectric function tensor from measurements parallel and perpendicular to the crystal’s optic axis using a transfer matrix algorithm. Comparison to the ZnO bandstructure and first-principles dielectric function (DF) calculations provides evidence for inter-valence-band transitions of "hot" charge carriers near the M point in the Brillouin zone. They are governed by selection rules for dipole transitions for perpendicular and parallel light polarization which cause the transient optical anisotropy.