Graphene transport at high carrier densities using a polymer electrolyte gate

We report the study of graphene devices in Hall-bar geometry, gated with a polymer electrolyte. High densities of 6×10 13 /cm 2 are consistently reached, significantly higher than with conventional back-gating. The mobility follows an inverse dependence on density, which can be correlated to a dominant scattering from weak scatterers. Furthermore, our measurements show a Bloch-Grüneisen regime until 100 K (at 6.2×10 13 /cm 2 ), consistent with an increase of the density. Ubiquitous in our experiments is a small upturn in resistivity around 3×10 13 /cm 2 , whose origin is discussed. We identify two potential causes for the upturn: the renormalization of Fermi velocity and an electrochemically enhanced scattering rate.