Carrier Densities and Mobilities in Pyrolytic Graphite

Abstract

Based on conductivity, Hall effect, and magnetoresistance measurements an attempt is made to describe the behavior of current carriers in the layer planes of well-ordered pyrolytic graphite. The total carrier concentration decreases from approximately 11\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ at room temperature to less than 4\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ at very low temperatures, in good agreement with single-crystal results. The average mobility, which is strongly dependent upon the crystallite size, was found to exceed 3000 ${\mathrm{cm}}^{2}$/v-sec at liquid nitrogen temperature in specimens deposited at 2500\ifmmode^\circ\else\textdegree\fi{}C; the mobility ratio ($\frac{{\ensuremath{\mu}}_{e}}{{\ensuremath{\mu}}_{h}}$) appears to remain temperature independent and equal to 1.08\ifmmode\pm\else\textpm\fi{}0.01.