Correlated conductivity and work function changes in epitaxial graphene

Correlation between conductance and surface work function (SWF) changes caused by molecular adsorption on epitaxial graphene on both faces of 6 H-SiC has been investigated. The SWF and conductance changes, explained on the basis of graphene band diagram, indicate C-face multilayer and Si-face few layer graphene behave as p and n-type sensing layers, respectively. A quantitative model correlating conductance and SWF changes has been proposed within the framework of Boltzmann transport theory. Our results further indicate that for epitaxial graphene, the charge interaction by the adsorbed molecules and related work function changes can be strongly influenced by the SiC substrate. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691628]