Polaron coupling in graphene field effect transistors on patterned self-assembled monolayer

Abstract

We investigated the device characteristics of a graphene field effect transistor (FET) of which interfaces were controlled by a self-assembled monolayer (SAM). Electrical transport measurements together with Raman spectroscopy characterizations for bilayer graphene (BLG) and single layer graphene (SLG) on micro-patterned SAM (mp-SAM), respectively, elucidate spatial carrier modulations on the graphene sheets driven by mp-SAM. The SLG–mp-SAM-FET device exhibits unconventional graphene p–n junction characteristics depending on the polarity of source–drain voltage. The observed characteristics can be interpreted as a velocity saturation of hole carriers coupled with polaron states, of which phonon energy is around 30 meV, on the SAM molecules at the graphene p–n junction. The SAM-based micro fabrication techniques presented in this report not only provide a spatial control of electronic properties for graphene but also lend a new perspective in the understanding of graphene–substrate interface based molecular self-assembled systems.