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TT: Fachverband Tiefe Temperaturen

TT 66: 2D Materials: Electronic structure, excitations, etc. – Poster (joint session O/TT)

TT 66.23: Poster

Mittwoch, 11. März 2026, 18:00–20:00, P2

Layer thickness dependent band gap of MBE grown single- to few-layer MoS₂ — •Maciej Bazarnik¹, Marta Przychodnia^1,2, Thorsten Deilmann³, and Anika Schlenhoff¹ — ¹Institute of Physics, University of Münster, Germany — ²Institute of Physics, Poznan University of Technology, Poland — ³Institute of Solid State Theory, University of Münster, Germany

In light of the rise of transition metal dichalcogenides as 2D semiconductors for device applications, band engineering becomes very important from an application point of view. In many of these materials, such as the canonical example of MoS₂, the semiconductor band gap depends on the layer number. There is a transition from an indirect band gap semiconductor in bulk to a direct band gap for a monolayer. Interestingly, it was predicted and experimentally confirmed that, by thinning the material from bulk to a bilayer, the indirect transition blue-shifts.

Here, we present the results of scanning tunnelling spectroscopy measurements on MoS₂ that has been grown in situ via molecular beam epitaxy (MBE) on graphene on Ir(111) at thicknesses ranging from 1 to 6 layers. We observe a decrease in the band gap with increasing layer number. We also find a pinning of the conduction band, which vanishes for layer thicknesses beyond 4 layers. Comparing our experimental data with DFT and GW calculations indicates that a screening in addition to that of the substrate needs to be introduced to explain the experimentally obtained relation. We discuss possible sources of this additional screening in light of our findings.

Keywords: scanning tunneling spectroscopy; transition metal dichalcogenides; electronic structure; 2D materials