physica status solidi (a)
Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Editor: Stefan Hildebrandt (Editor-in-Chief)
Online ISSN: 1862-6319
Back Cover (Phys. Status Solidi A 9/2010)
Different mechanisms of doping graphene are studied by Pinto et al. (pp. 2131–2136) using density functional theory. A first type can be called electronic doping and occurs when there is a direct exchange of electrons between graphene and an adsorbate. Examples are electronegative molecules like F4-TCNQ and electropositive metals like K which lead to p- and n-type doped graphene, respectively. The cover image shows the wavefunctions of the electronic levels of a K atom on top of graphene at the Brillouin zone point marked as A and is clearly localised on the K atom while the wavefunction of the level marked as B is delocalised over the graphene layer. Such doping occurs promptly, leads to a reduction in the carrier mobility, and there should be no hysteresis effects. Furthermore, a novel doping mechanism is exhibited by Au which dopes bilayer graphene but is less effective for a single layer. A third mechanism of doping graphene, electrochemical doping, occurs by redox reactions on the graphene surface. It can result in p-doping by humid atmosphere or n-doping by NH3 and toluene. This mechanism of doping requires appreciable time to occur and can lead to an increase in the carrier mobility and hysteresis effects.