Electronic Conductivity Upturn of HOPG Contrast to Transport Properties of Polycrystal Graphite

TL;DR

This study compares the transport properties of HOPG and polycrystal graphite, revealing differences in conductivity, magnetoresistance, and magnetic-field-induced transitions due to distinct underlying mechanisms.

Contribution

It provides a comparative analysis of transport behaviors in HOPG and polycrystal graphite, highlighting the role of Coulomb interactions versus grain boundary scattering.

Findings

HOPG exhibits higher electrical conductivity than polycrystal graphite.

Polycrystal graphite shows semiconductor-like behavior over a wide temperature range.

HOPG uniquely exhibits magnetic-field-induced metal-semiconductor transition.

Abstract

The transport properties of highly oriented pyrolitic graphite (HOPG) and polycrystal graphite have been studied. The electric conductivity of HOPG is several times larger than that of the polycrystal graphite. Along with the large magnetoresistances (MR), the polycrystal graphite show the accordant semiconductor-like character in a wide temperature (roughly range from 20K to 120K) under 0, 4, 8, 12 T applied magnetic field, while the magnetic-field-induced metal-semiconductor-like transition was only found in HOPG. The difference of transport properties originates from the Coulomb interaction quasipartical in HOPG graphite layers in contrast with the grain boundary scattering in the polycrystal graphite.