g-factor of current carriers in pyrolytic carbons with quasi-two-dimensional graphite structure

Abstract

The measurements of the g-factor in the temperature range from 3.8 to 1000 K have been carried out in highly textured pyrolytic carbons using electron spin resonance (ESR) technique. The main part of the ESR absorption is due to the current carriers whose g-factor has a considerable anisotropy (Δgc) associated with the two-dimensional orbital motion of electrons. The magnitude and temperature dependence of Δgc are determined by the fraction of unpaired electrons occupying states in the vicinity of the contact of the valence and conduction bands. An increase in the concentration of electrically active structure defects or boron admixture in the pyrocarbons results in the Fermi level shift deeper into the valence band and in a drastic drop of Δgc. To explain the Δgc behavior in pyrocarbons, especially at low temperatures, it is suggested to take into account the effective "smearing" of the density of states in the vicinity of the band contact associated with the carrier scattering by defects. © 1988.