Saturday, September 9, 2017
Abstract-Contactless graphene conductivity mapping on a wide range of substrates with terahertz time-domain reflection spectroscopy
Hungyen Lin, Philipp Braeuninger-Weimer, Varun S. Kamboj, David S. Jessop, Riccardo Degl’Innocenti, Harvey E. Beere, David A. Ritchie, J. Axel Zeitler, Stephan Hofmann
We demonstrate how terahertz time-domain spectroscopy (THz-TDS) operating in reflection geometry can be used for quantitative conductivity mapping of large area chemical vapour deposited graphene films on sapphire, silicon dioxide/silicon and germanium. We validate the technique against measurements performed with previously established conventional transmission based THz-TDS and are able to resolve conductivity changes in response to induced back-gate voltages. Compared to the transmission geometry, measurement in reflection mode requires careful alignment and complex analysis, but circumvents the need of a terahertz transparent substrate, potentially enabling fast, contactless, in-line characterisation of graphene films on non-insulating substrates such as germanium.