  Graphene devices on standard SiO2 substrates are highly disordered,
exhibiting characteristics far inferior to the expected intrinsic properties of
graphene[1-12]. While suspending graphene above the substrate yields
substantial improvement in device quality[13,14], this geometry imposes severe
limitations on device architecture and functionality. Realization of
suspended-like sample quality in a substrate supported geometry is essential to
the future progress of graphene technology. In this Letter, we report the
fabrication and characterization of high quality exfoliated mono- and bilayer
graphene (MLG and BLG) devices on single crystal hexagonal boron nitride (h-BN)
substrates, by a mechanical transfer process. Variable-temperature
magnetotransport measurements demonstrate that graphene devices on h-BN exhibit
enhanced mobility, reduced carrier inhomogeneity, and reduced intrinsic doping
in comparison with SiO2-supported devices. The ability to assemble crystalline
layered materials in a controlled way sets the stage for new advancements in
graphene electronics and enables realization of more complex graphene
heterostructres.
