Evidence for semiconducting behavior with a narrow band gap of Bernal graphite

We have studied the resistance of a large number of highly oriented graphite samples with areas ranging from several mm(2) to a few mu m(2) and thickness from similar to 10 nm to several tens of micrometers. The measured resistance can be explained by the parallel contribution of semiconducting graphene layers with low carrier density < 10(9) cm(-2) and the one from metallic-like internal interfaces. The results indicate that ideal graphite with Bernal stacking structure is a semiconductor with a narrow band gap E-g similar to 40 meV.