Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 19: 2D Materials Beyond Graphene II

O 19.5: Talk

Monday, March 20, 2017, 17:00–17:15, REC/PHY C213

Second-harmonic imaging microscopy: a powerful tool for time-resolved investigation of electron dynamics in TMDC heterostructures — •Jonas Zimmermann, Gerson Mette, and Ulrich Höfer — Philipps-Universität Marburg, Germany

Since the discovery of extraordinary luminescence of MoS2 monolayers, 2D transition metal dichalcogenides (TMDC) have been in the spotlight of the materials science community. In particular, heterostructures of different 2D materials attract attention due to their possible application in optoelectronics. As the efficiency of such devices is expected to depend strongly on the relative orientation of the individual layers, experimental techniques to characterize the electron transfer dynamics in dependence on the stacking angle are required.
Here, we present results of our new SHG imaging microscopy setup for time-resolved studies on interfaces of 2D materials. This technique allows us to quantify the crystal structure via polarization dependent measurements and gives us access to the electron dynamics via time-resolved pump-probe experiments. We demonstrate its capabilities with measurements performed on CVD grown WS2 and MoS2 monolayer flakes. The optical excitation tuned to 2.1 eV matches the energies of A- and B-exciton of WS2 and MoS2, respectively. Strong pump-induced features are observed and assigned to exciton generation. The excitonic lifetimes of the two materials correspond to values obtained in linear optical spectroscopy. The results reveal that SHG imaging microscopy is ideally suited to explore the effects of layer stacking on the charge transfer within 2D heterostructures.