Transport properties of bilayer graphene decorated by K adatoms in the framework of Thomas-Fermi screening

Abstract

We report the transport properties of bilayer graphene (BLG) due to the increase of Coulomb potential fluctuations and the decrease of K adatom concentration $({\mathrm{n}}_{\mathrm{K}})$ induced by diffusion and cluster formation of the K adatom as a function of temperature (20--300 K) and time at room temperature (RT). Upon K adatom deposition on BLG at $T=20$ K, conductivity decreased due to the emergence of Coulomb scatterers, and the dependence of conductivity transformed from linear $(\ensuremath{\sigma}\ensuremath{\sim}{n}^{\ensuremath{\alpha}},\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha}\ensuremath{\sim}1)$ to superlinear $(\ensuremath{\alpha}\ensuremath{\sim}1.5)$. As the inhomogeneity of the Coulomb potential on BLG increased by cluster formation of K adatoms, the magnitude of the conductivity increased, and the dependence of conductivity on charge carrier density (curvature) shifted towards linear behavior. We fit the experimental data with Boltzmann transport theory to show that the changes in the transport properties of BLG in the presence of charged impurities originate from two factors, ${\mathrm{n}}_{\mathrm{K}}$ and the Thomas-Fermi screening vector $({\mathrm{q}}_{\mathrm{TF}})$, which are both affected by cluster formation of K adatoms on BLG and the subsequent increase of Coulomb potential inhomogeneity.