Electronic Properties of Well Oriented Graphite

Abstract

IT has recently become apparent that conventional interpretations1,2 of Hall effect and magnetoresistive phenomena in graphite are consistent neither with one another nor with current ideas on the locations of electrons and holes within the Brillouin zone. Our Shubnikov–de Haas measurements on irradiated pyrolytic and single-crystalline graphite support the reassignment of the positions of the electron and hole Fermi surfaces made by Schroeder et al.3. We have also obtained evidence that apparent contradictions between the low field Hall coefficients of pyrolytic and single-crystalline graphites1,2 represent genuine extremes of behaviour. Studies in this laboratory of the anisotropy of the pressure dependence of conduction4,5 have suggested that electron-hole scattering of majority carriers is more important than carrier–phonon interactions6–8 in the basal planes, while at the same time the drag effect of majority on minority carriers9 is unimportant in explaining the low field Hall effect. A potentially confusing situation has thus arisen.