Mechanisms of doping graphene

We distinguish three mechanisms of doping graphene. Density functional theory is used to show that electronegative molecules like tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) and electropositive metals like K dope graphene p- and n-type, respectively. These dopants are expected to lead to a decrease in carrier mobility arising from Coulomb scattering but without any hysteresis effects. Secondly, a novel doping mechanism is exhibited by Au which dopes bilayer graphene but not single layer. Thirdly, electrochemical doping is effected by redox reactions and can result in p-doping by humid atmospheres and n-doping by NH3 and toluene. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim