Esquinazi

"The intrinsic carrier density of Graphite, a
two-dimensional gapless semiconductor"

A. Arndt, D. Spoddig, P. Esquinazi, J. Barzola-Quiquia, and T. Butz


We investigate the dependence of the electrical resistivity of  $\sim
60~$nm thick single crystalline graphite samples on the defect
concentration produced by a microbeam of 2.25 MeV protons at
very low fluences. We show that the resistivity decreases few
percent at room temperature
after inducing defects at concentrations as low as $\sim 0.1~$ppm due
to the increase in the carrier density, in agreement with theoretical
estimates. The overall results indicate that the usual carrier densities
measured in graphite are not intrinsic but related to defects and
impurities.