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

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 R_K 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 R_K 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 R_K 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 R_K. It was found that the strain part of the grain-boundary energy is correlated with the measured twist-angle-dependent R_K.