Charged impurity scattering in bilayer graphene

TL;DR

This study investigates how charged impurities affect charge transport in bilayer graphene, showing experimental results consistent with theory but indicating other factors also influence pristine material properties.

Contribution

It provides experimental evidence on charged impurity effects in bilayer graphene and compares findings with theoretical models, highlighting additional factors in pristine samples.

Findings

Charged impurity scattering causes supra-linear conductivity in BLG.

Minimum conductivity decreases with impurity concentration as n_imp^-1/2.

Impurity effects align with theory but do not fully explain pristine BLG transport.

Abstract

We have examined the impact of charged impurity scattering on charge carrier transport in bilayer graphene (BLG) by deposition of potassium in ultra-high vacuum at low temperature. Charged impurity scattering gives a conductivity which is supra-linear in carrier density, with a magnitude similar to single-layer graphene for the measured range of carrier densities of 2-4 x 10^12 cm^-2. Upon addition of charged impurities of concentration n_imp, the minimum conductivity Sigma_min decreases proportional to n_imp^-1/2, while the electron and hole puddle carrier density increases proportional to n_imp^1/2. These results for the intentional deposition of potassium on BLG are in good agreement with theoretical predictions for charged impurity scattering. However, our results also suggest that charged impurity scattering alone cannot explain the observed transport properties of pristine BLG on SiO2 before potassium doping.