Thermal Transport across Liquid-Solid Interface with a Single-Atomic Structure Based on the Radial Density Depletion Length at a Surface Solid Atom

Thermal management of interfaces is crucial because thermal boundary resistance (TBR) is dominant in the overall thermal resistance. Most studies on thermal transport at solid-liquid interfaces have focused on solid surfaces with crystal planes or structures measuring a few nanometers in size, and the influence of the surface structure of a single-atomic structure on the interfacial thermal transport remains unclear. This study investigated the TBR at Si-H2O interfaces with single-atomic structures (steps, clusters, and adatoms). Conventional density depletion length (DDL) was found to be unsuitable for evaluating thermal transport performance of surfaces with atomic structures. Therefore, we developed radial DDL, defined at each surface solid atom (RDDL), which is applicable to cases wherein single-atomic structures exist on a planar solid surface. The TBR decreased when single-atomic structures were attached to a surface with a high surface density at the atomistic scale. The developed RDDL, calculated focusing on each surface solid atom, exhibited a property similar to that exhibited by conventional DDL. The thermal transport decreased with an increase in the RDDL. Thus, RDDL facilitated a comprehensive understanding of precise thermal transport properties at the single-atomic scale via the simple measurement of the density distribution at solid-liquid interfaces.