Flux-Selected Titanyl Phthalocyanine Monolayer Architecture on Ag (111)

The adsorption and molecular architecture of titanyl phthalocyanine (TiOPc) monolayer films on Ag (111) have been studied with scanning tunneling microscopy. Depending on deposition flux, TiOPc selectively forms three distinct ordered monolayer structures. At lower (<0.1 ML/min) fluxes, molecules assemble into a well-ordered (2 root 13 x 2 root 13)R13.9 degrees honeycomb phase comprised of interlocked molecular pairs. This pairing effectively reduces the repulsion between the intrinsic molecular dipole and enhances the attraction between aromatic rings. At intermediate (0.2 ML/min) fluxes, molecules form a metastable (root 21 x root 21)R10.9 degrees hexagonal phase of uniformly tilted TiOPc. At higher (0.4 ML/min) fluxes, a misfit dislocation triangular network appears, consisting of uniformly sized TiOPc domains. Molecular models for the three distinct monolayer films are developed. We describe how local electrostatic intermolecular interactions stabilize kinetically accessible structures, driving phase selection.