Abstract:

The adsorption and chiral features of a self-assembled CuPc monolayer on a semi-metallic Bi(111) surface have been evaluated using the low temperature scanning tunneling microscopy (LT-STM). Under low coverage conditions, the individual CuPc molecules rotated around the molecular center at 78 K until they interacted with other molecule to form clusters, because of the relatively weak interfacial interactions between the CuPc molecules and the Bi(111) surface. As the level of molecular coverage increased, the CuPc molecules self-assembled into two-dimensional domains with each molecule exhibiting chiral features. Beyond one monolayer, the CuPc molecules underwent an orientational transition from a flat-lying to a standing-up configuration. The chiral features of the CuPc molecules were attributed to the combined effect of asymmetric charge transfer between the CuPc molecules and the Bi(111) substrate and the formation of asymmetric intermolecular van der Waals interactions.

Key words: CuPc, Scanning tunneling microscopy, Semi-metallic Bi(111), Chiral feature, Self-assembly