Pentacene-based nanorods on Au(111) single crystals: Charge transfer, diffusion, and step-edge barriers

Abstract

We investigate nanorod assemblies of two δ 4-substituted pentacenes, namely (2,3-X 2-9,10-Y 2)-substituted pentacenes with X = Y = OCH3 (MOP) and with X = F, Y = OCH3 (MOPF), grown on Au(111) single crystals. By using a multi-technique approach based on ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption, we find evidence for charge transfer screening at the interface with gold. Furthermore, the MOP and MOPF nanorods show a rough surface morphology, which was investigated with atomic force microscopy. We use molecular simulation techniques to investigate the energetic barriers to diffusion and to traverse step-edges to estimate their influence on the nanorod roughness. We find that barriers to surface diffusion on a terrace are anisotropic and that their direction favors the formation of nanorods in these materials.