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O: Fachverband Oberflächenphysik

O 72: Scanning Probe Techniques I: STM-ESR and Method Development (joint session O/CPP)

O 72.7: Vortrag

Mittwoch, 18. März 2020, 16:30–16:45, TRE Ma

Mapping the perturbation potential of metallic and dipolar tips in tunneling spectroscopy on MoS₂ — •Christian Lotze, Nils Krane, Gaël Reecht, Nils Bogdanoff, and Katharina J. Franke — Freie Universität Berlin, Germany

Single layer molybdenum disulfide (MoS₂) features a direct band gap and strong spin-splitting of the valence band at the K-point, which make it an interesting material for optoelectronic applications.

We grow a single layer of MoS₂ epitaxially on a Au(111) surface, adopting a recipe from [1], and employ its decoupling properties for high resolution scanning tunneling spectroscopy of single molecules [2]. Because of the band gap and small electron-phonon coupling strength of MoS₂, it is possible to resolve spectral features down to few meV. Differential conductance spectra of 2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene (BTTT) molecules exhibit a multitude of sharp characteristic peaks, originating from vibronic states. Indeed, these allow even for an identification of different rotamers [2].

Here, we make use of these vibronic fingerprints to investigate the influence of the tip potential on the apparently shifted molecular states along the extended molecular backbone of BTTT. Our analysis further allows us to distinguish between the inhomogeneous shape of the bias potential in the junction and possible intrinsic tip dipoles [3].

[1] Sørensen, et al., Langmuir, 31, 35, 9700 (2015)

[2] Krane, et al., ACS Nano, 12, 11, 11698 (2018)

[3] Krane, et al., Phys. Rev. B, 100, 035410 (2019)