▎ 摘　　要

Ambient-environment Kelvin probe microscopy of many (10 mu m)(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 (<10(12) 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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3595360]