Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 94: Focus Session: Proximity Effects in Epitaxial Graphene I
O 94.3: Vortrag
Donnerstag, 21. März 2024, 15:45–16:00, MA 141
Pb-intercalated epitaxial graphene on SiC: Charge transfer mechanism and spin-split interlayer bands — •Bharti Matta1, Philipp Rosenzweig1, Kathrin Küster1, Craig Polley2, and Ulrich Starke1 — 1Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — 2MAX IV Laboratory, Lund, Sweden
Intercalation of epitaxial graphene is a robust way of modifying its properties and stabilizing two-dimensional (2D) interlayers at the graphene/SiC interface. Pb being a heavy element superconductor has a great potential as an intercalant due to possible proximity effects in graphene. In this work, angle-resolved photoelectron spectroscopy (ARPES) shows that the near charge-neutrality of Pb-intercalated quasi-freestanding monolayer graphene on SiC (Pb-QFMLG) involves charge transfer from both interlayer-Pb and SiC. This is based on the observation that at 20 K, the p-doping of Pb-QFMLG increases by ≈ 9 × 1010 cm-2 compared to room temperature, which can be attributed to the freezing out of SiC bulk n-dopants. The bands of interlayer-Pb cross the Fermi level, confirming its metallic nature. ARPES in the repeated Brillouin zone confirms the (1×1) alignment of Pb relative to SiC. Constant initial state mapping as a function of photon energy reveals dispersionless Pb bands, corroborating their 2D nature. Potassium adsorption results in predominant charge transfer into graphene, inducing a strong n-doping of ≈ 1014 cm-2. Further, spin-resolved ARPES uncovers a strong spin splitting of the interlayer bands. However, any proximity-induced spin splitting in graphene is still ambiguous. This ongoing work is supported by DFG through FOR 5242.
Keywords: Epitaxial graphene; Pb intercalation; Band structure; ARPES; SpinARPES