Atomistic insights into dynamic growth of pentacene thin films on metal surfaces functionalized with self-assembled monolayers

Abstract

The fabrication of high-quality organic semiconductor thin films has crucial impact on the electrical properties of organic electronic devices. Here, we provide atomistic insights into dynamic growth of pentacene thin films on different Au surfaces functionalized with self-assembled monolayers (SAMs). First, disordered crystal structures are formed on both bare Au and smooth SAM functionalized Au surfaces, while the upright crystalline islands emerge on rough SAM surfaces. During the growth process on rough SAM surfaces, organic semiconductor molecules undergo the nucleation and reorientation, and eventually form thin films with terrace morphologies. In addition, the interaction energies among pentacene molecules and between pentacene and SAM molecules will affect the formation and reorientation of the seed nucleus. Furthermore, the effect of substrate temperature on the pentacene growth is also evaluated. The high substrate temperature delays the onset of nucleus reorientation but accelerate the reorientation process. Finally, free energy calculations demonstrate that the surface roughness plays an important role in the formation and orientation of the seed nucleus. Meanwhile, the energy barrier at the step edge of the terrace morphology can prevent molecules from crossing the step edge.