In-situ terahertz optical Hall effect measurements of ambient effects on free charge carrier properties of epitaxial graphene

Sean Knight, Tino Hofmann, Chamseddine Bouhafs, Nerijus Armakavicius, Philipp Kühne, Vallery Stanishev, Ivan G. Ivanov, Rositsa Yakimova, Shawn Wimer, Mathias Schubert, Vanya Darakchieva

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Abstract

Unraveling the doping-related charge carrier scattering mechanisms in two-dimensional materials such as graphene is vital for limiting parasitic electrical conductivity losses in future electronic applications. While electric field doping is well understood, assessment of mobility and density as a function of chemical doping remained a challenge thus far. In this work, we investigate the effects of cyclically exposing epitaxial graphene to controlled inert gases and ambient humidity conditions, while measuring the Lorentz force-induced birefringence in graphene at Terahertz frequencies in magnetic fields. This technique, previously identified as the optical analogue of the electrical Hall effect, permits here measurement of charge carrier type, density, and mobility in epitaxial graphene on silicon-face silicon carbide. We observe a distinct, nearly linear relationship between mobility and electron charge density, similar to field-effect induced changes measured in electrical Hall bar devices previously. The observed doping process is completely reversible and independent of the type of inert gas exposure.

Original languageEnglish (US)
Article number5151
JournalScientific reports
Volume7
Issue number1
DOIs
StatePublished - Dec 1 2017

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Knight, S., Hofmann, T., Bouhafs, C., Armakavicius, N., Kühne, P., Stanishev, V., Ivanov, I. G., Yakimova, R., Wimer, S., Schubert, M., & Darakchieva, V. (2017). In-situ terahertz optical Hall effect measurements of ambient effects on free charge carrier properties of epitaxial graphene. Scientific reports, 7(1), [5151]. https://doi.org/10.1038/s41598-017-05333-w