Phonon transport effects in one-dimensional width-modulated graphene nanoribbons

Abstract

We investigate the thermal conductance of one-dimensional periodic widthmodulated graphene nanoribbons using lattice dynamics for the phonon spectrum and the Landauer formalism for phonon transport. We conduct a full investigation considering all relevant geometrical features, i.e. the various lengths and widths of the narrow and wide regions that form the channel. In all cases that we examine, we find that widthmodulation suppresses the thermal conductance at values even up to ~70 % below those of the corresponding uniform narrow nanoribbon. We show that this can be explained by the fact that the phonon spectrum of the width-modulated channels acquires less dispersive bands with lower group velocities and several narrow bandgaps, which reduce the phonon transmission function significantly. The largest degradation in thermal conductance is determined by the geometry of the narrow regions. The geometry of the wider regions also influences thermal conductance, although modestly. Our results add to the ongoing efforts in understanding the details of phonon transport at the nanoscale, and our conclusions are generic and could also apply to other one-dimensional channel materials.