Rostock 2019 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 18: Posters 2: Time Resolved Spectroscopy
MO 18.9: Poster
Mittwoch, 13. März 2019, 16:15–18:15, S Foyer LLM
Ultrafast Electronic Dynamics and Optical Excitation of Phonons in Hafnium Disulfide Crystals — •Simon Unger1, Franziska Fennel1, Chris Rehhagen1, Tim Völzer1, Kai Rossnagel2, and Stefan Lochbrunner1 — 1Institute for Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock — 2Institute for Experimental and Applied Physics, University of Kiel, Leibnizstr. 19, 24118 Kiel
Transition metal dichalcogenides feature unique electronic and optical properties. Additionally, they consist of a layered structure, allowing the preparation of atomically thin crystals. Hafnium disulfide, as a representative of those materials, is considered to be a promising candidate for electronic and optoelectronic applications. To investigate the internal electronic processes and decay dynamics, static absorption and femtosecond pump-probe measurements were performed.
In the absorption spectrum, two bands are observed in the UV range. In the femtosecond pump-probe experiments, the sample is excited in the range of those bands and probed by a following white light pulse. The transient absorption signal shows a strong reduction in absorbance in the region of the original absorption, whereas at longer wavelengths a signal increase appears. This feature is an indication for a band gap renormalization induced by the population of excited charge carriers. The temporal evolution exhibits a fast sub-picosecond and a slower sub-nanosecond decay, caused by the relaxation and recombination of the charge carriers. Furthermore, the time traces show an oscillation pattern, which can be attributed to the excitation of acoustic phonons.