Kelvin probe microscopy and electronic transport in graphene on SiC(0001) in the minimum conductivity regime

Ambient-environment Kelvin probe microscopy of many (10 μm)2 areas of single-layer graphene on SiC(0001) shows area-to-area rms surface potential variation of 12 meV. Electronic transport data are consistent with the minimum conductivity regime. Together the data indicate a highly uniform carrier concentration with a small magnitude (<1012 cm−2). We conclude that the previously reported large spread in carrier densities from Hall measurements on similar samples is an artifact of electron–hole puddling in the minimum conductivity regime.