Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 66: Poster Wednesday: 2D Materials

O 66.10: Poster

Mittwoch, 3. April 2019, 17:45–20:00, Poster B2

Layer dependent properties of quasi-freestanding 2H-TaS₂ investigated with STM and STS — •Camiel van Efferen¹, Joshua Hall¹, Clifford Murray¹, Matthias Rolf¹, Niels Ehlen¹, Jun Li¹, Jan Berges², Erik van Loon², Tim Wehling², Alexander Grüneis¹, and Thomas Michely¹ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Institut für Theoretische Physik, Bremen Center for Computational Materials Science, Universität Bremen, Germany

We epitaxially grow quasi-freestanding TaS₂ multilayers on graphene on Ir(111) and investigate their thickness dependent properties up to three layers.
Using scanning tunnelling microscopy we observe the monolayer to be in the expected 3 × 3 charge density wave (CDW) phase, whereas the bilayer unexpectedly shows a 2 × 2 superstructure. Furthermore, the moiré of Gr on Ir(111) is no longer visible through the bilayer. Due to finite bilayer island sizes confinement effects occur, which interact with the superstructure.
We probe the electronic structure with low temperature scanning tunnelling spectroscopy, and find a strongly decreased density of states around the Fermi energy, as would be expected for a CDW. The width of the gap is compared with its monolayer analogue. We disentangle contributions from intrinsic bilayer properties, stacking effects and local confinement effects to the electronic structure.