Zinc(II) Tetraphenylporphyrin on Ag(100) and Ag(111): Multilayer Desorption and Dehydrogenation

The interactions between zinc­(II) tetraphenylporphyrin (ZnTPP) molecules and the Ag(100) and Ag(111) surfaces were investigated using a combination of scanning tunneling microscopy as a local probe of the molecular adsorption configuration and X-ray, ultraviolet, and inverse photoemission spectroscopies as probes of the electronic structure. For each surface, a monolayer of ZnTPP, formed by multilayer desorption, exhibits a highly ordered structure in registry with the underlying surface lattice. Subsequent annealing leads to a transition from intact molecular adsorption to dehydrogenation and subsequent rehybridization. This rehybridization is both intramolecular, with a flattening of the molecules and a measurable alteration of the electronic structure, and intermolecular, leading to two-dimensional growth of extended covalently bound structures

Chemical Interaction, Space-Charge Layer, and Molecule Charging Energy for a TiO₂/TCNQ Interface

Three driving forces control the energy level alignment between transition-metal oxides and organic materials: the chemical interaction between the two materials, the organic electronegativity, and the possible space charge layer formed in the oxide. This is illustrated in this study by analyzing experimentally and theoretically a paradigmatic case, the TiO₂(110)/TCNQ interface; due to the chemical interaction between the two materials, the organic electron affinity level is located below the Fermi energy of the <i>n</i>-doped TiO₂. Then, one electron is transferred from the oxide to this level and a space charge layer is developed in the oxide, inducing an important increase in the interface dipole and in the oxide work function