Probing the interaction at the C60-SiC nanomesh interface

Abstract

Synchrotron-based high-resolution photoemission spectroscopy (PES) and in situ scanning tunneling microscopy (STM) are used to investigate the interaction at the C60-SiC nanomesh interface during the sequential deposition and subsequent desorption of C60 molecules. A weak charge transfer occurs at the C60-nanomesh interface, involving electrons transferring from nanomesh to C60 overlayer. The interface interaction originated from the weak charge transfer at the C60-nanomesh interface is stronger than C60 intermolecular interaction (e.g., van-der-Waals force), facilitating the layer-by-layer growth for the first two layers of C60 on SiC nanomesh. The highly corrugated nanomesh surface results in an anisotropic diffusion and high diffusion barrier of C60 on top, and thereby leads to the formation of irregularly shaped C60 islands under submonolayer condition. In contrast, C60 diffusion on HOPG and Ag(1 1 1) surfaces is rather isotropic, resulting in the formation of hexagonally shaped C60 islands with smooth domain boundaries. STM results show the partial desorption of C60 molecules from the SiC nanomesh surface after annealing the 1 ML C60 sample (complete wetting layer of C60 on SiC nanomesh) at around 150 °C for 20 min. Thorough desorption of C60 molecules and full recovery of the clean SiC nanomesh are observed after annealing at around 200 °C for 20 min. In situ PES and STM experiments clearly demonstrate that C60 adsorption and desorption processes do not affect the underlying SiC nanomesh structure, revealing its thermal stability and chemical inertness to C60 molecules. © 2007 Elsevier B.V. All rights reserved.