kinetic Monte Carlo Multiscale Simulation of Atomic Layer Deposition in High-Aspect-Ratio Nanochannels

Atomic layer deposition (ALD) has become a versatile technique for atomic-level material synthesis and surface modification, with broad relevance in applications such as energy storage devices, integrated circuits, and membranes. The deposition is governed by a multitude of factors spanning multiple length/time scales, ranging from macroscopic transport phenomena to atomistic surface reactions. Owing to the intricate process coupling across these scales, a comprehensive evaluation of atomistic behavior under flow conditions remains highly challenging. To address this issue, a multiscale integrated simulation framework is developed in which precursor transport within high-aspect-ratio nanochannels is explicitly simulated using a finite volume method (FVM) and subsequently coupled with kinetic Monte Carlo (kMC) simulations to evaluate film growth characteristics. Based on the FVM results, the spatiotemporal distribution of precursor partial pressures along nanochannels is extracted and employed as input for a lattice-based kMC model, enabling atomistic resolution of the ALD process over the full deposition cycle. By coupling these two scales, key deposition metrics including step coverage and its temporal evolution under varying partial pressure conditions are quantitatively obtained, together with atomic-level smoothness and vacancy ratio. The kMC simulations further enable detailed visualization of film growth behavior on substrates under different precursor partial pressure environments. The results indicate that, within the microstructure, even when the overall precursor exposure is comparable, films formed near the entrance exhibit superior surface structure, as evidenced by higher atomic-level smoothness and reduced vacancy ratio, compared to those at the bottom. This study provides an engineering-feasible framework for evaluating atomistic film properties in ALD processes by consistently integrating fluid transport and surface reaction kinetics.