Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 91: 2D materials beyond graphene: TMDCs, silicene and relatives III

O 91.1: Talk

Thursday, March 15, 2018, 10:30–10:45, MA 043

Structure and Electronic Properties of Intrinsic Defects in Single Layer Molybdenum Disulfide on Au(111) — •Christian Lotze, Nils Krane, Asieh Yousofnejad, Gael Reecht, and Katharina J. Franke — Fachbereich Physik, Freie Universität Berlin, Germany

Transition metal dichalcogenides (TMDCs) are two-dimensional materials with a natural band gap, making them interesting as sensors, solar cells or LEDs. Single layer molybdenum disulfide (MoS₂) is especially interesting, because it provides a direct band gap [1] and a strong spin-splitting of the valence and conduction band.

Here we grow MoS₂ epitaxially on a Au(111) surface as described in [2]. Using combined scanning tunneling/atomic force microscopy (STM/AFM) at low temperatures, we observe different kinds of defects. Particularly prominent are defects, which appear in sizes of several nanometers. NC-AFM reveals an atomically intact surface layer, suggesting that the origin of the defect is located at the gold interface. At these sites, the band gap of MoS₂ is significantly modified, pointing towards quasi-freestanding MoS₂ on a metal substrate [3]. Moreover, we identify single point defects like Mo and S vacancies by STM/AFM and tunneling spectroscopy. The latter two exhibit localized in-gap defect states, which agree well with simulations from density functional theory [4].

[1] Mak et al., PRL 105, (2010) 136805; [2] Sorensen, et al., ACS Nano 8, (2014) 6788; [3] Krane, et al., Nano Lett. 16, (2016) 5163; [4] González, al., Nanotechnology, 27 (2016), 105702