Carrier mobility and chemical doping level are essential figures of merit for graphene, and large-scale characterization of these properties and their uniformity is a prerequisite for commercialization of graphene for electronics and electrodes. However, existing mapping techniques cannot directly assess these vital parameters in a non-destructive way. By deconvoluting carrier mobility and density from non-contact terahertz spectroscopic measurements of conductance in graphene samples with terahertz-transparent backgates, we are able to present maps of the spatial variation of both quantities over large areas. The demonstrated non-contact approach provides a drastically more efficient alternative to measurements in contacted devices, with potential for aggressive scaling towards wafers/minute. The observed linear relation between conductance and carrier density in chemical vapour deposition graphene indicates dominance by charged scatterers. Unexpectedly, significant variations in mobility rather than doping are the cause of large conductance inhomogeneities, highlighting the importance of statistical approaches when assessing large-area graphene transport properties. 

1.  J. D. Buron et al., Nano Lett., 2012, 12, pp. 5074-5081

Jonas Buron is currently a Post Doctoral fellow at the Technical University of Denmark.  He is primarily interested in the ultrafast electronic and optical properties of atomically thin materials such as graphene. He received his M.Sc. degree in Physics from the Technical University of Denmark (2010) and a Ph.D. in Physics (2013) from the Technical University of Denmark where he studied the terahertz transport dynamics of graphene charge carriers. During his Ph.D, he spent 4 months in the Teraherz Optical Science laboratory at the iCeMS (Institute for Integrated Cell-Material Sciences) studying the terahertz nearfirled response of graphene flakes.