Two-Dimensional Island Shape Determined by Detachment

TL;DR

This study uses kinetic Monte Carlo simulations to show how anisotropic molecular detachment influences heteroepitaxial island shapes, revealing mechanisms behind observed asymmetries and alignments in island growth.

Contribution

It introduces a model incorporating anisotropic detachment to explain experimentally observed asymmetric island shapes in heteroepitaxial growth.

Findings

Detachment leads to more compact islands compared to purely diffusive growth.

Asymmetry in detachment causes one island edge to be smooth and the other dendritic.

Proximity of islands results in alignment due to detachment-driven molecule transfer.

Abstract

Effect of an anisotropic detachment on a heteroepitaxial island shape is studied by means of a kinetic Monte Carlo simulation of a square lattice gas model. Only with molecular deposition followed by surface diffusion, islands grow in a ramified dendritic shape, similar to DLA. Introduction of molecular detachment from edges makes islands compact. To understand an anisotropic island shape observed in the experiment of pentacene growth on a hydrogen-terminated Si(111) vicinal surface, asymmetry in detachment around the substrate step is assumed. Edge molecules detach more to the higher terrace than to the lower terrace. The island edge from which molecules are easy to detach is smooth and the one hard to detach is dendritic. If islands are close to each other, islands tend to align in a line, since detached molecules from the smooth edge of the right island are fed to the dendritic and fast growing edge of the left island.