SKM 2023 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 56: 2D Materials III: Growth, Structure and Substrate Interaction II (joint session O/CPP)
O 56.8: Vortrag
Mittwoch, 29. März 2023, 16:45–17:00, GER 37
Vanadium sulphides on graphene on Ir(111): polymorphs, charge density waves, layer dependency — •Camiel van Efferen1, Joshua Hall1, Virgínia Boix2, Tobias Wekking1, Nikolay Vinogradov3, Alexei Preobrajenski3, Jan Knudsen2, Jeison Fischer1, Wouter Jolie1, and Thomas Michely1 — 1Universität zu Köln — 2Lund University — 3MAX IV Laboratory
Among 2D materials, vanadium based compounds like VS2 have attracted substantial research interest due to their predicted electronically correlated and magnetic ground states. However, the charge density wave (CDW) in monolayer (ML) VS2 and VSe2 competes with predicted magnetic ground states. This has led to new research directions attempting to unlock the magnetic moment of the V atoms, e.g. via defect creation, alloying or the intercalation of atoms between VS2 layers.
Here, we present a comprehensive X-ray photoemission spectroscopy and scanning tunneling microscopy study of few-layer, quasi-freestanding V4S7 and V5S8 on Gr/Ir(111), which are created via annealing of stoichiometric VS2. Annealing ML VS2 without background S pressure removes S atoms from the top layer of VS2, creating the striped compound V4S7. In contrast, annealing ML VS2 in a S atmosphere forms V5S8, where V atoms have self-intercalated between the VS2 layers in a 2×2 pattern. Surprisingly, we find that V5S8 has a layer-dependent CDW at low temperature, with bilayer V5S8 exhibiting a √3×√3 CDW, while the trilayer hosts a striped CDW phase akin to that of ML VS2.