Nucleation and growth of thin films of rod--like conjugated molecules

TL;DR

This paper investigates the nucleation and growth mechanisms of thin films made from rod-like conjugated molecules, emphasizing the effects of molecular anisotropy and orientation transitions on film morphology.

Contribution

It introduces a detailed analysis of the growth modes and orientation control of rod-like organic molecules, highlighting challenges due to their one-dimensional nature.

Findings

Identification of growth modes specific to rod-like molecules

Insights into the transition between flat and upright orientations

Methods for controlling molecular orientation during film formation

Abstract

Thin films formed from small molecules rapidly gain importance in different technological fields. To explain their growth, methods developed for zero--dimensional atoms as the film forming particles are applied. However, in organic thin film growth the dimensionality of the building blocks comes into play. Using the special case of the model molecule para--Sexiphenyl, we will emphasize the challenges that arise from the anisotropic and one--dimensional nature of building blocks. Differences or common features with other rodlike molecules will be discussed. The typical morphologies encountered for this group of molecules and the relevant growth modes will be investigated. Special attention is given to the transition between flat lying and upright orientation of the building blocks during nucleation. We will further discuss methods to control the molecular orientation and describe the involved diffusion processes qualitatively and quantitatively.