Temperature dependence of electrical characteristics of metal-carbon nanowall contacts

Abstract

Electrical contacts to vertically-aligned nanographite structures, the so-called carbon nanowalls (CNWs), are studied in a temperature range of 25 °C to 300 °C using Ag, Au, and Mg as contact materials. The total resistance between a pair of metal electrodes on CNWs is regarded as the combination of serial resistances of CNWs and two metal-CNW contacts. The contact resistance and specific contact resistivity measured by the transmission line method and transfer line method, respectively, decrease with increasing temperature, with low thermal activation energies of the order of 10−2 eV. The contact resistance occupies a large portion of the total resistance between a pair of electrodes and dominates the current transport even at high temperatures, thus affecting electrical signal measurement in device applications profoundly. Little dependence of contact resistance upon work function of metal species is attributed to a semi-metallic feature of CNWs with a high degree of delocalization, overlap, and continuity of defect bands.