Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 99: 2D materials beyond graphene: TMDCs, silicene and relatives IV
O 99.3: Talk
Thursday, March 15, 2018, 15:30–15:45, MA 043
Direct determination of monolayer MoS2 and WSe2 exciton binding energies on insulating and metallic substrates — •Soohyung Park1,2, Niklas Mutz1, Thorsten Schultz1, Ali Han3,4, Areej Areej3,4, Lain-Jong Li3,4, Emil J. W. List-Kratochvil1, Patrick Amsalem1, and Norbert Koch1,2 — 1Humboldt-Universität, Berlin, Germany — 2Helmholtz-Zentrum für Materialien und Energie, Berlin, Germany — 3Research Center for Applied Sciences, Taipei, Taiwan — 4King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
Two-dimensional transition-metal dichalcogenides (2D TMDCs) are attractive candidates for next-generation optoelectronic devices due to their unique electronic and optical properties. To employ 2D TMDCs in optoelectronic devices, understanding the fundamental physical properties is necessary. In this regard, one key parameter is the exciton binding energy. It is the energy difference between the lowest-energy optical absorption (optical gap) and the charge transport energy gap (transport gap). In this contribution, we will present an experimental study combining angle-resolved direct and inverse photoelectron spectroscopy in order to measure the transport gap, and reflectance measurements for a determination of the optical gap. In this manner we are able to determine the exciton binding energy for two common 2D TMDCs, MoS2 and WSe2, on insulator and metal substrates. In addition, we will show that the dielectric environment of 2D TMDCs strongly impacts the transport gap while the optical gap is barely affected, indicating large exciton binding energy change.