Electrical detection of CF3Cl phase transitions on graphene

The temperature-dependent conductivity of bilayer graphene with adsorbed layers of the halocarbon molecule CF3Cl was studied under ultra high vacuum conditions. Upon warming CF3Cl sub-monolayer from 25 K, the electrical conductivity drops abruptly at 47K and exhibits additional inflection points at 60K and 69 K. CF3Cl multi-layers exhibit an abrupt conductivity gain at 54 K. These conductivity features correspond to known temperature-coverage phase boundaries for CF3Cl films measured on graphite. The changes in conductivity reflect changes in dielectric screening and disorder potential of the CF3Cl adlayer. The chemical specificity of phase transitions presents a basis for sensor selectivity. (C) 2013 AIP Publishing LLC.