  The intrinsic channel properties of monolayer and multilayer graphene were
systematically investigated as a function of layer number by the exclusion of
contact resistance using four-probe measurements. We show that the continuous
change in normalized sheet resistivity from graphite to a bilayer graphene is
governed by one unique property, i.e., the band overlap, which markedly
increases from 1 meV for a bilayer graphene to 11 meV for eight layers and
eventually reaches 40 meV for graphite. The monolayer graphene, however, showed
a deviation in temperature dependence due to a peculiar linear dispersion.
Additionally, contact resistivity was extracted for the case of typical Cr/Au
electrodes. The observed high contact resistivity, which varies by three orders
of magnitude (from ~103 to 106 Ohm micron), might significantly mask the
outstanding performance of the monolayer graphene channel, suggesting its
importance in future research.
