Verification of kinetic model for liquid molecule transport within adsorption layers on solid surfaces via molecular dynamics simulation

Abstract

In the manufacturing process of semiconductor devices, wet processes such as cleaning and chemical treatment on surfaces with nanoscale fine structures play a critical role. The mass transport within nanoscale structures exhibits properties different from those of bulk liquids, owing to the influence of layered adsorption structures of liquid molecules formed near solid–liquid interfaces. In this study, we interpreted transport phenomena near solid–liquid interfaces as successive hopping motions between adsorption layers (adsorption and desorption events) and expressed their frequency using rate constants. Furthermore, we developed a theoretical model to quantitatively predict these rate constants based on the Arrhenius equation and transition state theory (TST). To validate the constructed theoretical model, molecular dynamics (MD) simulations were performed for two representative systems: a simple model consisting of Pt as the solid wall and Ar as the liquid molecule, and a more realistic system with SiO2 and H2O. The results showed that the initial desorption from the adsorption layer can be well described by the theoretical model, whereas subsequent desorption proceeds more slowly than predicted. The observed discrepancy between the theoretical model and the simulations was attributed to the breakdown of the quasi-equilibrium assumption in TST for the molecules remaining in the adsorption layer. To interpret this mismatch, we proposed a conceptual model that focuses on molecular recrossing events at the adsorption-layer boundary. It is expected to provide useful guidance for future modeling of transport phenomena near solid surfaces.