Interplay of orientational order and roughness in simulated thin film growth of anisotropically interacting particles

TL;DR

This study uses kinetic Monte Carlo simulations to explore how anisotropic interactions influence the roughness and orientational order in thin film growth, revealing a transition from preferred orientation to non-equilibrium roughening and domain formation.

Contribution

It introduces a detailed simulation approach to analyze the interplay of anisotropic interactions, roughness, and order in thin film growth, highlighting the emergence of non-equilibrium effects at high anisotropy.

Findings

Anisotropy induces preferred molecular orientation in films.

Strong anisotropy leads to non-equilibrium roughening effects.

Domain nucleation and growth occur at high anisotropy levels.

Abstract

Roughness and orientational order in thin films of anisotropic particles are investigated using kinetic Monte Carlo simulations on a cubic lattice. Anisotropic next-neighbor interactions between the lattice particles were chosen to mimic the effects of shape anisotropy in the interactions of disc- or rod-like molecules with van-der-Waals attractions. Increasing anisotropy leads first to a preferred orientation in the film (which is close to the corresponding equilibrium transition) while the qualitative mode of roughness evolution (known from isotropic systems) does not change. At strong anisotropies, an effective step-edge (Ehrlich-Schwoebel) barrier appears and a non-equilibrium roughening effect is found, accompanied by re-ordering in the film which can be interpreted as the nucleation and growth of domains of lying-down discs or rods. The information on order and roughness is combined into a diagram of dynamic growth modes.