Tuning configurations and orbitals of vanadyl phthalocyanine on transition metals via surface alloy effect

Abstract

Fabrication of well-ordered molecular films and further tuning their structural and electronic properties is crucial in enhancing the performance of the on-based organic devices. Herein, by high-resolution scanning tunneling microscopy and density functional theory calculation, we demonstrate the on-surface fabrication of well-organized vanadyl phthalocyanine (VOPc) membranes with diverse characteristics on the binary alloy monolayer. The molecular configurations, structures, and orbitals are clearly clarified in the submolecular level. On Ag2Sb/Ag(111), the VOPc membrane exhibits the fourfold symmetric unit cell comprising one centered and four cornered O-up molecules with two distinct stacking orientations. On the contrary, on Cu2Sb/Cu(111), all VOPc molecules adopt the O-down configuration and uniform orientations. The tunneling conductance spectra unveil a semiconductor signature but with different occupied orbitals for both VOPc membranes. These contrasting features are resulted from the diverse molecule–substrate interaction relating to the different charge transfer of alloy surfaces. Our study may open up a new route for modifying the structures and electronic states of the molecular films by applying surface alloy effects.