Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 13: Poster Session I
HL 13.66: Poster
Monday, March 12, 2018, 17:30–19:30, Poster B
Time-resolved dielectric function tensor of m-plane ZnO studied by femtosecond spectroscopic ellipsometry — •Oliver Herrfurth1, Steffen Richter1, Mateusz Rȩbarz2, Miroslav Kloz2, Shirly Espinoza2, Jakob Andreasson2,3, Marius Grundmann1, and Rüdiger Schmidt-Grund1 — 1Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Linnéstraße 5, 04103 Leipzig — 2ELI Beamlines, Institute of Physics, Czech Academy of Science, Na Slovance 2, 182 21 Prague, Czech Republic — 3Condensed Matter Physics, Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
We report on femtosecond time-resolved spectroscopic ellipsometry measurements on a m-plane oriented ZnO single crystal. Our recently developed technique relies on a pump-probe scheme employing an amplified Ti:Sa laser (6 mJ,35 fs). Its third harmonic is used as pump pulse and its fundamental wavelength is used to create a supercontinuum white light probe by focussing onto CaF2. This method allows to probe a spectral range from 340 nm to 1000 nm with a single shot. The time resolution is estimated as 170 fs. We determine the complex dielectric function tensor from measurements parallel and perpendicular to the crystal’s optic axis using a transfer matrix algorithm. A crucial point is the depth-dependence of the model parameters imposed by the finite, temporally varying penetration depth of the pump and probe beam. The relaxation dynamics of the excited charge carriers are observed. In particular, the resonances of excitons and exciton-phonon complexes are suppressed and spectrally shifted.