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HL: Fachverband Halbleiterphysik

HL 47: 2D Materials: Heterostuctures

HL 47.4: Vortrag

Donnerstag, 21. März 2024, 15:45–16:00, EW 201

Distance dependence of the energy transfer mechanism in WS₂-graphene heterostructures — •David Tebbe¹, Marc Schütte¹, Kenji Watanabe², Takashi Taniguchi³, Christoph Stampfer¹, Bernd Beschoten¹, and Lutz Waldecker¹ — ¹2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany — ²Research Center for Functional Materials, National Institute for Materials Science, Japan — ³International Center for Materials Nanoarchitectonics, Japan

We investigate the mechanism of energy transfer in heterostructures of the two-dimensional semiconductor WS₂ and graphene with variable interlayer distances achieved through spacer layers of hexagonal boron nitride (hBN). Our analysis of the emission and absorption line widths reveals that the energy transfer is dominated by states outside the light cone, indicating a Förster transfer process. The dependence of luminescence intensity on interlayer distances above 1 nm can be quantitatively reproduced using recently calculated values of the Förster transfer rates of thermalized charge carriers and a constant radiative rate. However, at smaller interlayer distances, the experimentally observed transfer rates exceed the predictions and depend on excess energy and excitation density. We conclude that at these distances, the transfer is driven by non-thermalized charge carrier distributions, as the transfer probability of the Förster mechanism depends on the momentum of electron-hole pairs.

Keywords: TMDc; 2D materials; Energy transfer; Photoluminescence spectroscopy; Heterostructures