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O: Fachverband Oberflächenphysik

O 109: Focus Session: Proximity Effects in Epitaxial Graphene II

O 109.6: Talk

Friday, March 22, 2024, 12:15–12:30, MA 141

Conductivity of intercalated Pb-monolayer in proximity to graphene — •Markus Gruschwitz, Andreas Cordier, Tim Güldenpfennig, Sergii Sologub, and Christoph Tegenkamp — Institut für Physik, TU Chemnitz, Chemnitz, Germany

Densely-packed monolayer of Pb, intercalated below the buffer layer on 4H-SiC(0001), reveals a long range ordered quasi (10× 10) reconstruction, revealing charge neutral graphene and providing further exotic effects, e.g. spin-orbit coupling or a superconducting phase [1]. We investigated this 2D heterostructure in detail by means of in-situ multiprobe-STM as a function of tip geometry, tip spacing and temperature. Thereby, around 3.5 µm wide parallel terraces of intercalated graphene separated by narrow and less conductive barriers are formed, causing a tip-spacing dependent behavior from 1D to 2D and strong lateral anisotropy. We utilize finite element simulations to disentangle the different contributions and finally reveal the conductivity of the 2D heterosystem.

At room temperature the conductivity amounts to 600 kS/m. As the temperature is lowered, the conductivity decreases below 100 K similar to previous results [2]. Assuming combined transport channels in the metallic Pb layer and graphene, the increase in resistance is not in agreement with former T-dependent resistance measurements of monolayer graphene. We rather assume a small gap in the range of 2.5 meV in graphene, e.g. induced by spin-orbit coupling into graphene.

[1] Adv. Mater. Interfaces 10, 2300471 (2023); [2] Materials 14, 7706 (2021)