Shubnikov-de Haas oscillations in neutron-irradiated graphite

Shubnikov-de Haas oscillations have been observed in rho xx (H) with single-crystalline graphite and in rho zz (H) with well oriented pyrolytic graphite. Exposure to fast neutron bombardment at approximately 303 K up to a total dose of 1.12*10 17 nvt produces electron acceptors which lower the Fermi energy, thus expanding the hole Fermi surface and contracting the electron Fermi surface. The long period (ca. 2.1*10 -5 G -1 ) previously associated with majority electrons (m* c =0.039 m 0 ) is reduced by pre-irradiation, while the short period (ca. 1.6*10 -5 G -1 ) which had been attributed to majority holes (m* c =0.061 m 0 ) is increased. Electron and hole assignments must therefore be interchanged, with electron states now appearing at point K and hole states near point H of the Billouin zone.