Molecular Assemblies on Silicon via Silicon-Carbon Covalent Bonds

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Much attention is being denoted to the study on molecular-scale electronic devices. While the molecules having a S atom at the terminal are widely used to construct a two-terminal device with Au electrodes, the interface of Au-S has not been well characterized. Instead of the Au-S system, molecules covalently bound to silicon are thought to be a potential candidate to provide a stable interface for carrier injection into molecules. The advantages of the molecules/semiconductor system are as follows : (a) the interface is thermally and chemically stable, (b) the electric properties can be controlled by doping electron-donating or -withdrawing impurities, and (c) micro- and nano-fabrication techniques established in the field of semiconductor devices are applicable. We have prepared molecular assemblies on silicon via chemical reaction between molecules having double bonds at the terminal and hydrogen-terminated silicon and studied reaction mechanism and stability by attenuated total ref … More lectance infrared (ATR-IR) spectroscopy and atomic force microscopy (AFM). In this work, we have demonstrated the following results : (1) alkyl-chains on silicon have an all-trans conformation ; (2) monolayers prepared in diluted 1-alkene were identical with that prepared in neat 1-alkene ; and (3) the rate of reaction between 1-alkene and hydrogen-terminated silicon remarkably depended on the concentration of 1-alkene. We have prepared a monolayer of dye molecules on silicon through anchoring molecules. The intensity of luminescence from the molecules on silicon was found to be strongly affected by the impurity concentration of silicon wafers used. We have also demonstrated that the silicon AFM cantilevers covered with organic molecules are available for friction-force microscopy and non-contact AFM in air as well as in ultrahigh vacuum. It has been shown that the cantilevers covered with organic monolayers via covalent bonds are useful for chemical force microscopy with contact and non-contact modes AFM in various atmospheres since the interface between molecules and cantilevers is thermally and chemically stable. Less