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Register a new userTwo-dimensional connective nanostructures of electrodeposited Zn on Au(111) induced by spinodal decomposition
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Phase-formation of surface alloying by spinodal decomposition has been studied for the first time at an electrified interface. For this aim Zn was electrodeposited on Au(111) from the ionic liquid AlCl3-MBIC (58:42) containing 1 mM Zn(II) at different potentials in the underpotential range corresponding to submonolayer up to monolayer coverage. Structure evolution was observed by in situ electrochemical scanning tunneling microscopy (STM) at different times after starting the deposition via potential jumps and at temperatures of 298 K and 323 K. Spinodal or labyrinth two-dimensional structures predominate at middle coverage, both in deposition and dissolution experiments. They are characterized by a length scale of typically 5 nm which has been determined from the power spectral density of the STM images. Structure formation and surface alloying is governed by slow kinetics with a rate constant k with activation energy of 120 meV and preexponential factor of 0.17 Hz. The evolution of the structural features is described by a continuum model and is found to be in good agreement with the STM observations. From the experimental and model calculation results we conclude that the two-dimensional phase-formation in the Zn on Au(111) system is dominated by surface alloying. The phase separation of a Zn-rich and a Zn-Au alloy phase is governed by 2D spinodal decomposition.
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Pinning single molecules at desired positions can provide opportunities to fabricate bottom-up designed molecular machines. Using the combined approach of scanning tunneling microscopy and density functional theory, we report on tip-induced anchoring of Niphthalocyanine molecules on an Au(111) substrate. We demonstrate that the tip-induced current leads to the dehydrogenation of a benzene-like ligand in the molecule, which subsequently creates chemical bonds between the molecule and the substrate. It is also found that the diffusivity of Ni-phthalocyanine molecules is dramatically reduced when the molecules are anchored on the Au adatoms produced by bias pulsing. The tip-induced molecular anchoring would be readily applicable to other functional molecules that contain similar ligands.
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