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O: Fachverband Oberflächenphysik
O 87: Mini-Symposium: Infrared nano-optics I
O 87.5: Talk
Thursday, March 4, 2021, 12:15–12:30, R2
Tunable s-SNOM for nanoscale infrared optical measurement of electronic properties of bilayer graphene — •Konstantin G. Wirth1, Heiko Linnenbank2,3, Tobias Steinle2,3, Luca Banszerus4, Eike Icking4, Christoph Stampfer4, Harald Giessen2,3, and Thomas Taubner1 — 1Institute of Physics (IA), RWTH Aachen — 24th Physics Institute and Research Center SCoPE, University of Stuttgart, 70569 Stuttgart — 3SI Stuttgart Instruments GmbH, 70771 Leinfelden-Echterdingen — 42nd Institute of Physics (IIA), RWTH Aachen University, 52074 Aachen
The stacking and rotation of individual graphene layers changes its band structure, opening up new physical properties. Local probing of their electronic properties at the nanoscale is usually done by scanning tunneling microscopy, which requires electrical contact. Optical measurements such as infrared absorption or Raman spectroscopy, work for non-contacted and encapsulated samples, but are limited in lateral resolution by diffraction to a few micrometer. Here we directly probe the electronic properties of bilayer graphene (BLG) using s-SNOM measurements with a broadly tunable laser source over the energy range from 0.3 to 0.54 eV. We tune an OPO/OPA system around the interband resonance of Bernal stacked BLG and extract amplitude and phase of the scattered light. This enables us to retrieve and reconstruct the complex optical conductivity resonance in BLG around 0.39 eV with nanoscale resolution. Our technique opens the door towards nanoscopic noncontact measurements of the electronic properties in complex hybrid 2D and van der Waals material systems.