Selective Adsorption of Pyridine at Isolated Reactive Sites on Si(100)

Abstract

Dative bonding of nitrogen-containing heterocycles offers a strategy for the controlled attachment of aromatic molecules to silicon surfaces. However, while scanning tunneling microscopy shows that pyridine on clean Si(100) initially binds via a dative bonding configuration, slow conversion to a more stable bridging state, destroying the aromaticity, is observed. To restrict adsorption to the dative bonded form, we investigated the interaction of pyridine with isolated reactive sites on partially H-terminated Si(100). While dative bonding on isolated clean dimers is observed, single dangling bonds remain unreacted. This selectivity can be accounted for by the ability of the Si-Si dimers to act as electron acceptors that stabilize the dative bonded species. This observation has important implications for the controlled positioning of single molecules on silicon via dative bonding. Recent adsorption studies of organic molecules on silicon surfaces have been largely motivated by the prospect of fabricating hybrid organic/silicon molecular devices.1-4 Aro-matic molecules are of particular interest for such applications because of their potential use as molecular wires or switches. Numerous studies have demonstrated that unsaturated molecule