Probing the interaction at the C60-SiC nanomesh interface

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.