Effect of annealing on the transport properties of HOPG

This paper studies the effect of annealing on the transport properties for the highly oriented pyrolytic graphite.Found that the annealing procedure could smooth the R-T curve of HOPG,doubling its resistivity,reducing its magnetoresistance by 40%.These could be attributed to the stacking-fault and impurities in the HOPG sample.Temperature dependence of the basal-plane resistivity reveals that the magnetic field restrains the metallic behavior of HOPG at low temperatures.The metallic behavior disappears under H=5.57×104A/m and a reentrant metallic behavior appears under H=9.24×105A/m with no dependence on the sample annealing,indicates that the I-M transition is a magnetic field induced phenomenon.