Chemical Functionalization and Surface Nanopatterning

Abstract

Single atom control on semiconducting surfaces represents a challenging task and an appealing strategy towards the development of hybrid organic–inorganic nanoelectronics at the atomic scale and the design of quantum information devices. It also offers the possibility to control chemical reactions selectively at the nanoscale. In particular, silicon dangling bonds (DBs) that are band gap electronic states in the Si(001) surface play a key role in these processes. Thus, in this article we present methods to generate patterns of DBs using water functionalization of the Si(001) surface. While hydrogen-saturated Si(001) surface requires scanning tunneling microscopy (STM) tip manipulation to generate localized DBs, a water-passivated Si(001) surface, (H, OH)-Si(001), offers virtually unlimited silicon isolated DBs (iDBs) and distinctive monohydrides (H–Si) and hydroxyl (HO–Si) patterns that can be identified clearly on this surface. They represent localized electronic sites with interesting chemical reactivity that was used for preferential growth of organic molecules. For example, the adsorption of benzaldehyde illustrates the role of iDBs as preferential nucleation sites without the risk of dissociation. In addition, the iDBs are described as remarkable localized atomic quantum states with unique electronic features. In addition, we show that atomic silicon DB nanowires can be generated when water is leaked at low doses in UHV on a pristine Si(001) surface. The (1D) atomic silicon DB nanowires which run along the dimer rows appear with bright protrusions in the empty-states STM image with remarkably high aspect ratio, with a maximum length of 30Å. Finally, patterning of a pristine Si(001)-(2×1) was achieved at room temperature using covalent dative bonding adsorption of triethylamine (TEA) molecules. Remarkably, this adsorption conserves the electronic coupling between the reacted dimer levels and those of the adjacent bare dimers. The patterning consists of a transition from the dynamic (2×1) structure, in which up-and-down oscillations of dimers takes place, to a statically buckled c(4×2) at room temperature. The geometric motion of TEA molecules were monitored in real time across this patterned c(4×2) surface.