Disentangling Phonon Channels in Nanoscale Thermal Transport

TL;DR

This paper investigates how surface and lattice phonon scattering mechanisms influence nanoscale heat transport, identifying a critical temperature where surface effects dominate, aiding the design of nanoscale thermal devices.

Contribution

It introduces a framework to disentangle phonon scattering mechanisms in nanowires by controlling atomic-level disorder without altering morphology or composition.

Findings

Identified a size-dependent critical temperature for phonon scattering dominance.

Mapped the temperature-thermal conductivity-diameter parameter space.

Demonstrated surface effects dominate above the critical temperature.

Abstract

Phonon surface scattering has been at the core of heat transport engineering in nanoscale structures and devices. Herein, we demonstrate that this phonon pathway can be the sole mechanism only below a characteristic, size-dependent temperature. Above this temperature, the lattice phonon scattering co-exist along with surface effects. By artificially controlling mass disorder and lattice dynamics at the atomic-level in nanowires without affecting morphology, crystallinity, chemical composition, and electronic properties, the temperature-thermal conductivity-diameter triple parameter space is mapped, and the main phonon scattering mechanisms are disentangled. This led to the identification of the critical temperature at which the effect of lattice mass-disorder on thermal conductivity is suppressed to an extent that phonon transport becomes governed entirely by the surface. This behavior is discussed based on Landauer-Dutta-Lundstrom near-equilibrium transport model. The established framework provides the necessary input to further advance the design and modelling of phonon and heat transport in semiconductor nanoscale systems.