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Hydrogen‐Intercalated Graphene on SiC as Platform for Hybrid Superconductor Devices

F. Paschke, T. Birk, S. Forti, U. Starke, and M. Fonin

Advanced Quantum Technologies 2020, 3, 2000082, DOI:10.1002/qute.202000082

Nanodevices based on hybrid graphene–superconductor structures have recently attracted much attention owing to both fundamental and application aspects. However, atomic‐level investigations of proximity‐induced superconductivity in graphene, especially on technologically relevant substrates remain rare. Here, the atomic‐scale study of electronic properties and the superconducting proximity effect in hydrogen‐intercalated single‐layer graphene on SiC decorated with epitaxial lead (Pb) islands is reported. The graphene layer is thoroughly characterized by means of Landau level spectroscopy which confirms its quasi‐free‐standing nature. Scanning tunneling spectroscopy performed at 1.8 K on the graphene layer in the vicinity of Pb islands shows a reduced superconducting gap of Δ_gr=0.20(1) meV, which points to a graphene/superconductor junction of moderate transparency. The variations of the proximity‐induced superconducting gap on graphene are measured as function of spatial position as well as of magnetic field strength. Spatially resolved measurements yield a coherence length of about 175 nm in the graphene monolayer. The study provides a foundation for realization of graphene–superconductor heterostructures on large‐scale SiC(0001) wafers suitable for future technological applications.