How to Achieve High Quality Large Area Monolayer Graphene with Field Effect Mobility of 20,000 cm2/Vs

High quality graphene monolayers were grown using chemical exfoliation method by sonicating the highly ordered pyrolytic graphite in organic solvents. Properties of as exfoliated graphene layers were found to be strongly dependent on dielectric constant of the solvents. This was corroborated by confocal Raman spectroscopy and electrical measurements. Graphene samples exfoliated in solvents with low dielectric constant show diminutive D band intensities and excellent field effect mobility of 20,000 cm

2

/Vs and in solvents with high dielectric constant, D band intensity increases and mobility reduces to 11,000 cm

2

/Vs due to doping induced defects in graphene layers. Our results also show up shift in minimum conductivity point with doping level due to inhomogeneous potential induced by point defects near Dirac point.