Molecular dynamics simulations of pentacene thin film growth: Stability of nuclei comprising standing molecules and their subsequent growth

Abstract

Molecular dynamics (MD) simulations were applied to the study of nucleation and growth of pentacene thin films, and stability of clusters (nuclei) comprising standing molecules was investigated. In simulations, the clusters consisting of more than ten standing molecules could stably exist on hydrophobic surfaces, while several tens of molecules were necessary for stabilization on hydrophilic surfaces. Furthermore, the stabilized clusters could grow by incorporating additional molecules in MD simulations. These results suggest that nucleation occurs on hydrophobic surfaces easier than on hydrophilic surfaces and the critical size of the nuclei of “standing” pentacene is about ten molecules on hydrophobic surfaces.

Cocrystal Growth in Organic Semiconductor Thin Films: Simulation of Pentacene, Perfluoropentacene, and Their 1:1 Blend Deposited On Graphite

“…In crystalline films on smooth and defect‐free graphite surfaces, the molecular long axes of PFP and PEN are expected to be parallel to the substrate, while heating or the presence of structural defects [ 41 ] that increase surface roughness favor an organization with an upright molecular orientation, typical of acenes on other rough surfaces (e.g., SiO 2 ). [ 17–42 ] In fact, while the chemical similarity between the deposited molecules and graphite promotes a recumbent alignment, an upright one allows exposing to air a lower energy surface. The unbalance between the two energies and kinetic factors determines the outcome; however, since at low submonolayer coverages the recumbent orientation is always thermodynamically favorite, for subsequently obtaining the upright one the temperature should be high enough to allow the initially recumbent molecules to overcome a collective energy barrier for reorientation.…”

“…In this context, atomistic simulations already proved to be a valid option for the prediction and the understanding of the underlying mechanisms of the on‐surface crystal growth. [ 14–22 ] Concerning the deposition of mixed systems, although simulations of solid mixtures of organic molecules are becoming increasingly popular, in particular for better understanding the functioning of organic LEDs and solar cells at the nanoscale, [ 23,24 ] we are not aware of any theoretical investigation on the formation of organic semiconductor mixed crystals from vapor phase.…”

Water permeation pathways in laminated organic single-crystal devices

“…The determined molecular structures, including the values of the partial charge, were kept during the MD simulations (rigid model). The full details of the MD simulations are explained elsewhere, 31,32 however, briefly, the water-water interaction was calculated based on the TIP5P potential, 33 and the intermolecular and molecule-substrate interactions were described by the Lennard-Jones potential, as well as Coulomb interactions that were summed up within the cut-off distance of 1 nm. Under these simulation conditions water molecules have been confirmed to form a massive aggregate on a hydrophobic surface and to spread over a hydrophilic surface, 31 which validates the employed conditions for the MD simulations.…”

Nonequilibrium Roughness Evolution of Small Molecule Mixed Films Reflecting Equilibrium Phase Behavior

“…As detailed molecular simulations of binary growth systems with realistic parameters are currently out of reach, this strategy appears to be most appropriate for elucidating the universal patterns that we see. Currently, specific growth effects in one-component systems can be investigated using molecular dynamics simulations as recent examples for C60 growth or pentacene growth ,, show. Generic effects, however, could only be addressed by extending simulations to mixtures and treating a wide range of molecular species and compositions, which appears to be unrealistic.…”