Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: 2D Materials Beyond Graphene I

O 8.1: Talk

Monday, March 20, 2017, 10:30–10:45, REC/PHY C213

A monolayer of MoS₂ on Au(111) as a decoupling layer for single molecules — •Christian Lotze, Nils Krane, Robert Steyrleuthner, Robert Bittl, Jan Behrends, and Katharina J. Franke — Fachbereich Physik, Freie Universität Berlin

Thiophene based molecules are commonly used for semiconducting devices like solar cells or light emitting diodes. In order to optimize these, a detailed understanding of the molecules electronic structure and the environmental influence on the latter is of great interest.

Scanning tunneling spectroscopy (STS) allows to address individual molecules in a precisely known surrounding. However, it bears the drawback that it requires a conductive substrate. Deposition of organic molecules on a metal substrate leads to strong hybridization of the electronic states. Preservation of the molecular character requires the inclusion of thin band-gapped materials.

Here, we present STS experiments performed on 2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene-n (BTTT-n; n=1,2) molecules adsorbed on a single layer molybdenum disulfide (MoS₂) on Au(111). We show that it acts as an effective decoupling layer. Differential conductance spectra of the molecules exhibit a multitude of sharp characteristic peaks, that are connected to the highest occupied molecular orbital. We propose that these originate from a surprisingly effective excitation of vibronic resonances by the tunneling electrons.