Anisotropic In-Plane Phonon Transport in Ultrathin Silicon Membranes Guided by Nano-Surface-Resonators

TL;DR

This paper introduces a novel method to induce anisotropic phonon transport in ultrathin silicon membranes using surface nanostructures, significantly affecting thermal conductivity directionally.

Contribution

The study demonstrates that surface nanofins can guide phonon transport anisotropically in quasi-2D silicon, a mechanism not previously established for isotropic 2D materials.

Findings

Thermal conductivity is ~50% higher parallel to nanofins.

Resonance hybridization with surface nanostructures guides phonons.

Anisotropic transport is achieved in ultrathin silicon membranes.

Abstract

Anisotropic phonon transport along different lattice directions of two-dimensional (2D) materials has been observed, however, the effect decreases with increasing the thickness beyond a few atomic layers. Here we establish a novel mechanism to induce anisotropic phonon transport in quasi-2D materials with isotropic symmetry. The phonon propagation is guided by resonance hybridization with surface nanostructures. We demonstrate that the thermal conductivity of 3 nm-thick silicon membrane with surface nanofins is greater by $\sim50\%$ parallel to the fins than that perpendicular to the fins.