Structure formation of C60 on insulating CaF2 substrates : matching experiments with simulations

Abstract

The epitaxial growth of metallic thin films has been studied intensively, leading to computational models that can predict diverse morphologies depending on thermodynamic and kinetic growth parameters. Much less is known about thin films of organic molecules. Here kinetic Monte Carlo simulations to study buckyball C60 molecules on dielectric CaF2(111) substrates is employed. This system undergoes a transition from mostly one-layered growth to two-layered growth of triangular cluster morphologies as the temperature is raised. Even though simplified, these simulations still require a large set of parametrized rates for the elementary transitions, the determination of which has been challenging. Here recent results for these parameters to measure cluster densities and second layer occupations are employed. Simulation snapshots of cluster morphologies are compared in a wide range of temperatures to test to which extent rate models can match the experimental observations. While adjustments to free diffusion parameters are necessary to reproduce the experimentally observed cluster densities and sizes, the cluster morphologies are excellently reproduced without further adjustments.