Shubnikov-de Haas oscillations in neutron-irradiated graphite

Abstract

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*10¹⁷nvt 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 m₀) 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 m₀) 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.