Surface phonon-polaritons enhance thermal conduction in SiN nanomembranes

TL;DR

This study experimentally demonstrates that surface phonon-polaritons significantly enhance thermal conduction in thin amorphous silicon nitride membranes, especially as the membrane thickness decreases and temperature increases.

Contribution

First experimental evidence showing that surface phonon-polaritons contribute to heat conduction in dielectric membranes, with conductivity doubling at high temperatures in thin SiN membranes.

Findings

Thermal conductivity increases with temperature due to SPhPs.

SPhPs contribution is more significant in membranes thinner than 100 nm.

Thermal conductivity can be doubled by SPhPs at high temperatures.

Abstract

Surface phonon-polaritons can carry energy on the surface of dielectric films and thus are expected to contribute to heat conduction. However, the contribution of surface phonon-polaritons (SPhPs) to thermal transport has not been experimentally demonstrated yet. In this work, we experimentally measure the effective in-plane thermal conductivity of amorphous silicon nitride membrane and show that it can indeed be increased by SPhPs significantly when the membrane thickness scales down. In particular, by heating up a thin membrane (<100 nm) from 300 to 800 K, the thermal conductivity increases twice due to SPhPs contribution.