Ballistic transport at room temperature in micrometer-size graphite flakes

The intrinsic values of the carriers mobility and density of the graphene layers inside graphite, the well-known structure built on these layers in the Bernal stacking configuration, are not well known mainly because most of the research was done in rather bulk samples where lattice defects hide their intrinsic values. By measuring the electrical resistance through microfabricated constrictions in micrometer small graphite flakes of a few tens of nanometers thickness we studied the ballistic behavior of the carriers. We found that the carriers' mean-free path is greater than or similar to 1 mu m large with a mobility mu similar or equal to 6 x 10(6) cm(2)/Vs and a carrier density n similar or equal to 7 x 10(8) cm(-2) per graphene layer at room temperature. These distinctive transport and ballistic properties have important implications for understanding the values obtained in single graphene and in graphite as well as for implementing this last in nanoelectronic devices.