Two-carrier model on the magnetotransport of epitaxial graphene containing coexisting single-layer and bilayer areas

We have performed low-temperature magnetotransport measurements on epitaxial graphene composed of domains of single-layer and bilayer areas simultaneously present on SiC(0001). Positive magnetoresistance that tends to saturate at high magnetic fields is observed for longitudinal component , while the Hall resistance exhibits sublinear behaviour. The lineshapes for both can be accounted for extremely well by the semiclassical magnetotransport model incorporating two types of carriers conducting in parallel. Two sets of mobilities and densities, corresponding to single-layer and bilayer regions, respectively, can be obtained by fitting the experimental traces to the two-carrier model formulae. From the carrier densities, in turn, the ratio of the single-layer to bilayer areas can be deduced, assuming the alignment of the Fermi levels in the two types of areas with differing dispersion relations and Dirac point energies. The ratio of areas thus obtained is consistent with the ratio directly observed in the atomic force micrograph.