New Quadratic Self-Assembly of Double-Decker Phthalocyanine on Gold(111) Surface: From Macroscopic to Microscopic Scale

Unveiling the self-organization mechanism of semiconducting organic molecules onto metallic surfaces is the first step to design hybrid devices in which the self-assembling is exploited to tailor magnetic properties. In this study, double-decker rare-earth phthalocyanines, namely, lutetium phthalocyanine (LuPc2), are deposited on Au(111) gold surface forming large-scale self-assemblies. Global and local experimental techniques, namely, grazing incidence X-ray diffraction and scanning tunneling microscopy, supplemented by density functional theory calculations with van der Waals corrections, give insight into the molecular structural arrangement of the thin film and the self organization at the surface. Our results show unambiguously that the two plateaus of the double-decker phthalocyanine present a different rotation than the isolated molecule. This is evidenced by density functional theory simulations of optimized LuPc2 monolayer showing a perfect agreement with experimental findings. Moreover, the stabilized structure of double layers reveals an eclipsed configuration of the molecules in the stacking, having the ligand plateaus parallel to the gold surface. The high crystallinity of the molecular assembly and its weak electronic coupling with the metallic substrate is expected to open new perspective in magnetic devices.