  We present measurements of the electric potential fluctuations on the surface
of highly oriented pyrolytic graphite using electrostatic force and atomic
force microscopy. Micrometric domain-like potential distributions are observed
even when the sample is grounded. Such potential distributions are unexpected
given the good metallic conductivity of graphite because the surface should be
an equipotential. Our results indicate the coexistence of regions with metallic
and insulating behaviors showing large potential fluctuations of the order of
0.25V. We discuss the implications of these measurements in the disorder
structure of graphite.
