Nonequilibrium classical molecular dynamics simulations were employed to investigate thermal transport across crystalline and amorphous silicon (a-Si) surfaces in contact with water for different interfacial bonding strengths. A spectral analysis of heat transfer across the different interfaces revealed the characteristics of the phonon modes contributing to thermal transport. Low-frequency modes contributed the most in hydrophobic interfaces, while a shift toward contribution from higher frequency modes was found for hydrophilic surfaces. The shift to higher frequency modes was not significant for a-Si and crystalline Si(111) interfaces. In-plane phonon modes significantly contributed to heat transfer in Si(100), less significantly in a-Si, and had a minimum contribution in Si(111) hydrophilic interfaces. While the wettability and solid-liquid bonding strength failed in explaining these observations, the interfacial liquid density depletion helped to understand the differences between Si(100) and a-Si interfaces with respect to the Si(111) interface. The interface liquid structure observed in the Si(100) but not in the a-Si system served as an explanation for the dominant contribution of in-plane modes in Si(100). These observations posed the density depletion and liquid structure at solid-liquid interfaces as useful parameters for explaining the underlying mechanisms of phonon transport at solid-liquid interfaces.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films