Strongly Reduced Thermal Conductivity of Supported Multilayer-Graphene Nanowires

Abstract

The thermal properties of two-dimensional (2D) materials are of fundamental interest for energy recovery and electron cooling at the nanoscale. Exploring thermal transport in 2D systems is a challenging issue particularly in the substrate-supported architecture, which is the most relevant for applications. In this configuration, heat diffusion is strongly affected by thermal losses through the substrate and highly depends on interfacial properties. Here we investigate thermal transport of supported few-layer graphene nanowires by the Joule self-heating method in the high-temperature range (400 K $<T<$ 500 K). This method is valuable for the substrate-supported sample configuration. By using a thick and rough oxide layer, we find that thermal losses through the substrate are reduced by almost 1 order of magnitude with respect to the expected theoretical values. Most importantly, we unveil an effective reduction of the thermal conductivity, with values as low as 40 W ${\mathrm{m}}^{\ensuremath{-}1}$ ${\mathrm{K}}^{\ensuremath{-}1}$, comparable to reported values for supported graphene nanoribbons. Such a reduction can be induced by increased phonon scattering with the substrate and impurities in the system, which is inherent to the device fabrication. Our findings should stimulate research on alternative solutions for energy conversion at the nanoscale using graphene and other 2D materials when deposited on substrates.