Invited Paper SS2-MoA3
The Cycloaddition of Organic Molecules to the Si(100)c(4x2) Surface: Microscopic Mechanism and Tunneling Properties of Single Molecules
Chemical modification of Si surfaces has attracted much attention from the view point of coating, sensors, molecule-based microelectronics and so on. The cycloaddition of organic molecules to the Si(100) surface is the most important family of chemical reactions for the modification of the Si surface as well as Lewis acid-base reaction, because the stable Si-C covalent bonds are formed between molecules and the surface. In the cycloaddition, the asymmetric dimer on the reconstructed Si(100) surface plays an important, in which a partial charge transfer occurs from a down dimer atom (Sd) to an up dimer atom (Su). The chemical nature of Sd and Su is electrophilic and nucleophilic, respectively; the asymmetric dimer may act as a zwitter ion. In this talk, first, we show some examples of regioselective cycloaddition reaction between asymmetric alkene molecules and the asymmetric dimer on Si(100)c(4x2) using low-temperature STM. The regioselective cycloaddition product may be controlled by a precursor state. Next, scanning tunneling spectroscopy (STS) results of a single adsorbed molecule will be presented. In some cases, interesting features are observed in I vs.V characteristics, which may be due to adsorbate derived local electronic states.