Suppressing phonon transport in nanowires: a simple model for phonon-surface roughness interaction

TL;DR

This paper presents a simple analytical model to understand how surface roughness suppresses phonon transport in nanowires, aiming to improve thermoelectric device efficiency by reducing thermal conductivity.

Contribution

The paper introduces a new, analytically tractable model for phonon-surface roughness interaction that explains experimental observations of reduced thermal conductivity in nanowires.

Findings

Surface roughness significantly reduces phonon thermal conductivity.

The model aligns well with experimental data on silicon nanowires.

Insights from the model can guide the design of more efficient thermoelectric materials.

Abstract

Suppressing phonon propagation in nanowires is an essential goal towards achieving efficient thermoelectric devices. Recent experiments have shown unambiguously that surface roughness is a key factor that can reduce the thermal conductivity well below the Casimir limit in thin crystalline silicon nanowires. We use insights gained from the experimental studies to construct a simple analytically tractable model of the phonon-surface roughness interaction that provides a better theoretical understanding of the effects of surface roughness on the thermal conductivity, which could potentially help in designing better thermoelectric devices.