Berlin 2024 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 33: 2D Materials and Heterostructures: Optoelectronics
HL 33.3: Talk
Wednesday, March 20, 2024, 15:30–15:45, EW 201
Near field photocurrent nanoscopy at a biased graphene interface junction — •Francesca Falorsi1, Marco Dembecki2, Christian Eckel1, Monica Kolek Martinez de Azagra1, and R. Thomas Weitz1 — 11st Institute of Physics, Faculty of Physics, Georg-August-University Göttingen, Göttingen — 2Physics of Nanosystems, Faculty of Physics, LMU Munich, Germany; current address. WSI, TUM, Garching, Germany
The nanoscale analysis of photocurrent is a versatile tool to gain information about electronic states, quantum processes, and device characteristics of quantum materials. When photocurrent is studied with a near-field scattering microscope (s-SNOM), it is possible to overcome the diffraction limit. Thus one can image the local characteristic of the devices with a 20 nm resolution. In this work, the analysis of s-SNOM images of the local photocurrent generated at mono-bi layer graphene interfaces is performed to gain a more profound knowledge of the specific mechanisms governing electronic flow and resistivity at a nanoscopic level. In particular, by analyzing the polarity of the photocurrent concerning the source-drain voltage applied across the device, it was possible to indirectly image the charge carrier accumulation around a defect during electronic charge flow, predicted by Landauer in 1957. It was found that for values of the Fermi energies in proximity to the charge neutrality point (i.e. at low hole or electron doping) the photocurrent has the same polarity as the applied source-drain voltage, as it would be expected for changes in carrier concentration induced by the LRD.
Keywords: Photo-current; Near field scattering microscope; Graphene