Temperature dependence of thermal resistance at the water/silicon interface

摘要

Molecular dynamics (MD) simulations of heat transport through a water-silicon system are performed to investigate the thermal resistance at water/silicon interface. Interaction strength between water and silicon is varied in order to understand its effects while the proper strength value is characterized by matching the nano-scale contact angle value with the micro-scale experimental measurements through a water droplet study. Depending on surface wettability, different water distributions are developed near the surface, creating different couplings between water and silicon molecules for phonon transport. In addition, near surface water density is found to be dependent on the surface temperature for high wetting cases that closer packing of water molecules is observed near the cold surface. Interface thermal resistance values measured as Kapitza length (L_K) showed strong dependence on water density structure formed next to the surface. Hence, variation of L_K with temperature is not only measured due to the temperature dependence of phonon transport, but also due to the variation of near surface density with temperature. For studied water/silicon system (slightly hydrophobic with contact angle of 88°), density is independent of surface temperature, and L_K decreases with increased temperature similar to the theoretical phonon transport predictions. MD predicted L_K values (≈9 nm) are found to be consistent with experimental measurements.