Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: 2D Materials Beyond Graphene IV
O 77.3: Vortrag
Mittwoch, 22. März 2017, 15:45–16:00, WIL A317
Semiconductor to Metal Transition in WS2/Ag(111) — •Charlotte E. Sanders1, Maciej Dendzik1, Albert Bruix1, Matteo Michiardi2, Arlette S. Ngankeu1, Marco Bianchi1, Bjørk Hammer1, Jill A. Miwa1, and Philip Hofmann1 — 1Department of Physics and Astronomy, Aarhus University, Denmark — 2Department of Physics and Astronomy, University of British Columbia, Canada
Substrate effects play an important role in determining electronic structure in two-dimensional materials (2DMATs). A common effect of a metallic substrate on a semiconducting 2DMAT is renormalization of the band gap, induced by metallic screening, as recently observed in MoS2/Au(111) [1]. Here we report a substrate effect that goes beyond band gap change due to screening. For WS2/Ag(111), hybridization between electronic states of Ag and WS2 leads to a non-zero density of states at the Fermi level (FL), and thus to a transition of WS2 from a direct band gap semiconductor to a metal. This is evidenced by the asymmetric lineshape observed in core-level photoemission spectra. It is associated particularly with the emergence of states at the FL near the Q point of WS2, as can be seen in measurements by angle-resolved photoemission spectroscopy (ARPES). Meanwhile, ARPES and time-resolved ARPES confirm that the WS2 conduction band minimum at K remains well defined and stays above the FL. Electronic structure calculations based on density functional theory shed further light on the reasons for these strong changes in band structure. [1] Phys. Rev. B 93, 165422 (2016)