Simulation of atomic layer deposition on cohesive porous particles during fluidization by coupling CFD-DEM with particle surface reactions

Abstract

Fluidized bed reactor atomic layer deposition (FBR-ALD) is a high-flux ALD for micro and nanoparticle substrates. The coverage uniformity and precursor utilization are critical factors in evaluating the quality and cost-effectiveness of FBR-ALD. In this study, the computational fluid dynamics-discrete element model (CFD-DEM) is employed to simulate the fluidization-ALD process of porous microparticles in a tiny fluidized bed. The mass gain of particles and evolution of gas species during completed ALD cycles including precursor exposures and inert gas purges are revealed. Effects of particle cohesion and precursor concentration on coating uniformity, particle growth rate, and precursor utilization are investigated. Both fluidization and reaction rate affect coating uniformity, while precursor utilization mainly depends on the precursor concentration during exposures. A decrease in cohesion or precursor concentration leads to improved coating uniformity. It is found that the correlation between precursor concentration and utilization is almost negative linear. Furthermore, based on the simulation data a prediction surface for recommended exposure time is proposed to minimize precursor waste. This study provides insights into precursor reactions and coating behaviors in ALD on fluidized particles.