Si thin film with nanohole structures to improve thermoelectric performance Part 1: Effects of shape and arrangement in periodic holes

Improvements in thermoelectric energy conversion are expected to enhance the performance of thermoelectric generators. The effective control of thermal transport is essential for such improvements. One of the popular methods is utilization of phonon scattering at nanoscale structural interfaces, an approach based on the differences in the mean free path (MFP) between phonons and electric charge carriers. Nanoscale structures effectively impede the transport of phonons with long MFPs by selectively reducing thermal conductivity while minimizing the impact on electrical conductivity. In this study, we investigated the effect of periodic holes in a two-dimensional silicon thin film on thermoelectric performance. Using the Boltzmann transport equation with relaxation time approximation, we simulated the effects of hole shapes and arrangements on thermal conductivity. We unexpectedly found that H-shaped holes, the notches of which are oriented perpendicularly to the heat flow, most effectively reduce thermal conductivity.