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O: Fachverband Oberflächenphysik

O 77: Poster Session - 2D Materials: Stacking and Heterostructures

O 77.6: Poster

Mittwoch, 18. März 2020, 18:15–20:00, P2/EG

A setup for time-resolved second-harmonic imaging microscopy to study charge-transfer processes in 2D heterostructures at cryogenic temperature. — •Marleen Axt, Ulrich Höfer, and Gerson Mette — Fachbereich Physik, Philipps Universität Marburg, Germany

Two dimensional materials like transition metal dichalcogenides (TMDC) have attracted tremendous interest in designing opto-electronic devices. Of special interest are vertically stacked 2D Van-der-Waals heterostructures and their charge-transfer processes including the formation of strongly bonded interlayer excitons. However charge transfer at atomically sharp interfaces has been found to be extremely rapid, occuring on a femtosecond time scale and therefore is rarely observed.

Here, we present an experimental setup to study ultrafast charge-transfer dynamics at cryogenic temperatures with time-resolved second-harmonic imaging microscopy. Symmetry-based nonlinear optical properties of 2D materials are used to determine the crystallographic orientation of individual layers. Pump-probe experiments are performed using a new laser system providing ultrashort laser pulses (< 30 fs) with tunable energies for both, pump and probe laser pulses. With high temporal and spatial resolution we investigate TMDC-monolayers and heterostructures including temperature-dependent measurements for systematic studies.