Contactless millimeter wave method for quality assessment of large area graphene

Abstract We demonstrate that microwave absorption experiments offer a route for efficient measurements of transport properties for fast and accurate quality control of graphene. This conctactless characterization method can be used to quickly evaluate transport properties over large areas without recourse to complex lithographic methods making it suitable as a probe of quality during wafer scale fabrication. In particular, we demonstrate that absorption measurement of transport properties is sensitive to inhomogeneities in sample transport properties. This is in contrast to traditional methods using electrical contacts which tend to overestimate transport properties due to the formation of preferential conducting channels between the electrodes. Here we compare Shubnikov–de Haas oscillations simultaneously detected by microwave absorption and by conventional contact Hall bar measurements in fields up to 15 T on quasi-free standing, large area ( 25 mm ² ) monolayer graphene. We find that although the evaluated charge carrier densities from both measurements are similar, the mobility differs considerably due to electronic transport inhomogeneity.