Size-dependent electrical and thermal conductivities of electro-mechanically-spun glassy carbon wires

While electrical and thermal properties of glassy carbon are critical to performance metrics and fabrication processes of various carbon-based electronic and sensing devices, their size and process dependencies remain unclear due to limited experimental reports. In particular, the thermal conductivity of glassy carbon has received very little attention. Here, we have simultaneously characterized the electrical and thermal conductivities of individual glassy carbon wires (GCWs) using controlled electromechanical-spinning and electrical-resistance thermometry techniques. Despite the lack of electron or phonon boundary scattering, the GCW electrical conductivity varies from 477 to 18,100 S/m and its thermal conductivity varies from 0.7 to 4Wm(-1)K(-1) at room temperature, and these variations present no direct correlations with the GCW's diameter (630 nm -3.5 mu m), length (28-220 mu m) or composition. We have identified empirical correlation fits with a volume change ratio that is induced by the carbonization process and we attribute the electrical and thermal conductivity variations to strain-driven volumetric changes in porosity and structural order. The experimental findings of this work enable precise understanding of electrical and thermal transport phenomena in glassy carbon and support developments of carbon-based micro-electro-mechanical systems for advanced electronic and sensing applications. (C) 2018 Elsevier Ltd. All rights reserved.