We investigate molecular adsorption, film growth, and selfassembly for titanyl phthalocyanine (TiOPc) on Cu(110) in ultrahigh vacuum using low-temperature scanning tunneling microscopy (LT-STM). Three unique molecular adsorption configurations are identified, two of which are referred to as "O-down" and one as "O-up", each differing in the molecular registry with the surface. Even though disorder dominates film growth to coverages in excess of 1 monolayer in the native thin film, extended self-assembled 1D configuration-dependent nanoribbons form upon annealing of the film. The STM data reveal that the nanoribbons consist of "O-down" TiOPc and a Cu skeleton, anchoring cooperatively on the Cu(110) terraces. Agent-based simulations show that nanoribbons grow and elongate due to anisotropic adatom attachment rates along the two major surface directions. The study reveals the importance of molecule− adatom interactions for novel approaches toward nanostructuring organic semiconductor/metal interfaces.

Switching the magnetic properties of organic semiconductors on a metal surface has thus far largely been limited to molecule-by-molecule tip-induced transformations in scanned probe experiments. Here we demonstrate with molecular resolution that collective control of activated Kondo screening can be achieved in thin-films of the organic semiconductor titanyl phthalocyanine on Cu(110) to obtain tunable concentrations of Kondo impurities. Using low-temperature scanning tunneling microscopy and spectroscopy, we show that a thermally activated molecular distortion dramatically shifts surface-molecule coupling and enables ensemble-level control of Kondo screening in the interfacial spin system. This is accompanied by the formation of a temperature-dependent Abrikosov-Suhl-Kondo resonance in the local density of states of the activated molecules. This enables coverage-dependent control over activation to the Kondo screening state. Our study thus advances the versatility of molecular switching for Kondo physics and opens new avenues for scalable bottom-up tailoring of the electronic structure and magnetic texture of organic semiconductor interfaces at the nanoscale.

We use low-temperature scanning tunneling microscopy in combination with angle-resolved ultraviolet and two-photon photoemission spectroscopy to investigate the interfacial electronic structure of titanyl phthalocyanine (TiOPc) on Cu(110). We show that the presence of two unique molecular adsorption configurations is crucial for a molecular-level analysis of the hybridized interfacial electronic structure. Specifically, thermally induced selfassembly exposes marked adsorbate-configuration-specific contributions to the interfacial electronic structure. The results of this work demonstrate an avenue towards understanding and controlling interfacial electronic structure in chemisorbed films even for the case of complex film structure.

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While it is becoming apparent that organic semiconductor / metal interfaces may exhibit a variety of different structural phases, it is at present unclear to what extent these different thin film structures determine the interfacial electronic structure. Here, we observe large changes in the interfacial electronic structure for the case of copper(II) phthalocyanine (CuPc) on Cu(110)-O(2x1). This striking evolution of the interfacial electronic structure occurs beyond the first monolayer of CuPc and is particularly evident in the frontier orbital region. Using scanning tunneling microscopy in conjunction with photoemission spectroscopy, we characterize ultrathin films of CuPc grown on oxygen reconstructed Cu(110). We propose that the observed unique changes to the electronic structure result from an abrupt transition in film structure between the first and second layers: An interface layer of ordered, face-on molecules templates a largely vertical, edge-on orientation of molecules in the subsequent layer. The quadrupole moment of the molecule accounts for the sizeable and unusual change in ionization energy between molecules in the two layers. Our results demonstrate that the precise structure of the organic semiconductor film exerts an important role in determining the interfacial electronic structure that must be considered and may be harnessed for tailoring energy level alignment at such interfaces.