Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Graphene: Electronic Structure and Excitations (joint session O/HL)

O 28.5: Talk

Tuesday, March 18, 2025, 11:30–11:45, H6

Polymorphism of a two-dimensional Pb layer underneath charge neutral graphene on SiC — •Markus Gruschwitz, Sergii Sologub, Zamin Mamiyev, Chitran Ghosal, and Christoph Tegenkamp — Institut für Physik, TU Chemnitz, Germany

Since the first studies on graphene, researchers strive to implement its unique properties in industrial relevant processes. The intercalation of epitaxially grown buffer layers on SiC results in high quality, quasi-freestanding graphene, which allows the electronic properties to be modified by varying the intercalants and their arrangement. Pb recently sparked a great interest by reliably providing almost perfectly charge neutral graphene. The Pb layer effectively screens the substrate induced doping. In a novel approach using differential phase contrast in cross-sectional scanning transmission electron microscopy we reveal their vertical charge density distribution. Surprisingly, the charge neutrality is robust against variations in the Pb interface reconstruction. Depending on the preparation, a Pb monolayer often reconstructed in two coexisting phases, the so-called stripe [1] or bubble [2] phase. Intercalated multilayers reveal a similar striped phase arising from two twisted plumbene layers [3]. Here we combine structural investigations by scanning tunneling microscopy and high-resolution low-energy electron diffraction in a model of flexibly arranged grain boundaries releasing lattice mismatch stress.

[1] Materials 14, 7706 (2021), [2] Adv. Mater. Interfaces 10, 2300471 (2023), [3] Phys. Rev. Lett. 129, 116802 (2022)

Keywords: epitaxial graphene; intercalation; high resolution electron diffraction; scanning tunneling microscopy; scanning transmission electron microscopy