Thermal transport in nanoporous holey silicon membranes investigated with optically-induced transient thermal gratings

TL;DR

This study employs a non-contact optical technique to measure phonon-mediated thermal transport in nanoporous silicon membranes and compares the results with ab initio calculations, confirming the adequacy of the Casimir framework at nanoscale dimensions.

Contribution

It demonstrates that the Casimir framework accurately models thermal transport in nanoporous silicon membranes with features around 100 nm, validated by experimental data.

Findings

Casimir framework matches experimental data

Thermal transport is phonon-mediated

Membrane dimensions influence thermal behavior

Abstract

In this study, we use the transient thermal grating optical technique \textemdash a non-contact, laser-based thermal metrology technique with intrinsically high accuracy \textemdash to investigate room-temperature phonon-mediated thermal transport in two nanoporous holey silicon membranes with limiting dimensions of 100 nm and 250 nm respectively. We compare the experimental results to ab initio calculations of phonon-mediated thermal transport according to the phonon Boltzmann transport equation (BTE) using two different computational techniques. We find that the calculations conducted within the Casimir framework, i.e. based on the BTE with the bulk phonon dispersion and diffuse scattering from surfaces, are in quantitative agreement with the experimental data, and thus conclude that this framework is adequate for describing phonon-mediated thermal transport through holey silicon membranes with feature sizes on the order of 100 nm.