C-Axis Thermoelectric Power of Highly Oriented Pyrolytic Graphite

Abstract

Thermoelectric power in c-direction (S_c) of highly oriented pyrolytic graphite (HOPG) exhibits a sharp negative dip around 20–30 K. This anomaly is ascribed to the phonon drag thermoelectric power (S_p) related to the out-of-plane vibration and S_p is calculated in close relation to the mechanism of c-axis conduction. Major contribution to S_c comes from S_p which can provide a qualitative explanation of the observed results.