Formation of Oriented Bilayer Motif: Vanadyl Phthalocyanine on Ag(100)

Abstract

The adsorption and self-assembly of vanadyl phthalocyanine molecules on Ag(100) has been investigated using a combination of scanning tunneling microscopy and density functional theory. At submonolayer coverage, we observe two distinct adsorption configurations of isolated molecules, corresponding to the central O atom pointing toward (“O-down”) or away (“O-up”) from the substrate. Upon adsorption in the O-up orientation, the otherwise achiral molecules take on a windmill-like chiral appearance due to their interaction with the substrate. At monolayer coverage, we observe a self-assembled square lattice with a mixture of O-up and O-down molecules. At higher coverage we find a strong preference for bilayer formation with O-up and O-down molecules in alternating layers, suggesting stabilization by dipolar interactions. Close inspection of the multilayer surface reveals grain boundaries separating domains of opposite organizational chirality, and long-range ordering. © 2024 American Chemical Society.