Recently, the research of orgainic-semiconductor hybrid system has been intensively attracted due to the possibility which can control various surface properties such as chirality, molecular recognition, conductivity, and nonlinear optical properties. Hence, many research groups, in these days, have been studied the adsorption structure of organic molecules, either planar or rigid, onto the semiconductor surface. Because the interaction between organic molecules and semiconductor surfaces is localized and directional, its characteristic behavior on semiconductor surface is clearly different from metal surfaces that it generally shows catalytic reactions.
Ge dimers of the reconstructed Ge(100) surface have two distinguishable interactions, which were noticed by a strong σ-bond and a week π-like interaction. In special, it is well known that the π-bond across the Ge dimer is shown to work particularly for the class of attachment reaction such as cycloaddition. On the other hand, the weakness of the π-bond allows the dimer on Ge(100) to tilt and this tilt imparts a zwitterionic-like property to the dimer with the dimer characterized by one electron-deficient atom and one electron-rich atom in the dimer. Hence, this electronic property of the Ge surface opens up possibilities of using nucleophilic and electrophilic attachment reactions. Up to now, most of the work done in this area only focus on the interaction between electrophilic down Ge atom and Lewis base molecules such as ammonia, trimethylamine, and pyridine on Ge(001). So, it is necessary to be understood the interaction between up Ge atom and acid molecules.
In this presentation, we will elucidate the mechanism for constructing alternative homogeneous molecular wire with selective adsorptions of Lewis acid (AlCl3) and base molecules (pyridine) on the Ge dimer using scanning tunneling microscopy (STM) and high-resolution core-level photoemission spectroscopy (HRPES). Such a self-assembly technique for formation of the one dimensional molecular wire in nanometer scale by Lewis acid - base interaction can give a useful information to other pairs of Lewis base and acid molecules.
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