Thermal boundary resistance correlated with strain energy in individual Si film-wafer twist boundaries

Abstract

Nanoscale interfaces, such as grain boundaries (GBs) within a polycrystalline material, play an important role in suppressing the phonon heat transport. The interfacial thermal resistance RK of a GB has a strong dependence on the detailed interfacial atomic structure, including the misorientation between two grains and GB dislocations. Along this line, numerous molecular dynamics simulations on RK have been carried out on a twist Si GB. Owing to the challenge of measuring such a GB within a bulk material, these simulations are rarely compared with experimental data. In this work, a super-flexible 70-nm-thick Si thin film was hot pressed onto a Si wafer to represent a twist GB. The RK of the film-wafer interface was measured as a function of the rotation angle between the film and the wafer. The experimental data were further compared with an analytical model to interpret the twist angle dependence of the measured RK. It was found that the strain part of the grain-boundary energy is correlated with the measured twist-angle-dependent RK.