Regensburg 2019 – wissenschaftliches Programm
O 17.1: Poster
Montag, 1. April 2019, 17:45–20:00, Poster F
Local charge transport in graphene devices mapped using Kelvin probe force microscopy — •Sayanti Samaddar1, Kevin Janßen1, Kai Sotthewes2, Zhenxing Wang3, Daniel Neumaier3, Marcus Liebmann1, and Markus Morgenstern1 — 1II. Institute of Physics B, RWTH Aachen University and JARA-FIT, Otto-Blumenthal-Str., 52074 Aachen, Germany — 2Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands — 3Advanced Microelectronic Center Aachen (AMICA), AMO GmbH, Otto-Blumenthal-Str. 25, 52074 Aachen
Graphene based field effect transistors (FETs) and diodes were investigated using KPFM in combination with transport. Imaging FETs, at different source to drain voltages, enables a mapping of local voltage drops occurring at various surface perturbations like defects, impurities, and wrinkles. In the regions between graphene wrinkles and the contacts, a strong enhancement of the potential gradients along the direction of current flow is observed. The response of these local voltage drops to a global back-gate is also investigated. In the second part, diodes comprised of titanium - titanium oxide - graphene heterostructures are studied, where gate voltages induce variations in the graphene work-function resulting in their superior asymmetry in comparison to metal-insulator-metal diodes . We observe significant doping disorder ~ 50 meV on the graphene, which systematically decrease as the diode is tuned from the off state to the on state.
 M. Shaygan et al., Nanoscale 9, 11944 (2017)