Modeling and measuring nanoscale thermal transport in silicon membranes New Submission

The performance of semiconductor nanotechnologies is often limited by the thermal management. Across nanometer length scales and in highly confined geometries, thermal phonon transport deviates significantly from traditional diffusive descriptions, and no theoretical consensus exists on how to correctly model these systems. We review theoretical tools for modeling heat transport in silicon thin films, and present new measurements of effective in plane thermal conductivity of ultrathin silicon membranes¹. Current experimental techniques generally either obscure intrinsic behavior with interfaces, or lack sufficient spatial resolution to differentiate between transport models. Our transient grating apparatus uses a novel all reflective geometry to enable optical heterodyne measurements of a gratings generated by 200nm femtosecond pulses on the tabletop². In the context of our measurements of silicon membranes, we evaluate the merits and limitations of approximate solutions to the Boltzmann Transport Equation (BTE), including phonon hydrodynamics with the Guyer-Krumhansl equation, and a ballistic model under the relaxation time approximation (RTA).

 

 

¹Beardo et al. npj Comput. Mater. 11, 172 (2025), ²Nelson et al. Phys. Rev. Applied. 22, 054007 (2025).