Self-assembled monolayers (SAMs) offer many useful applications in the form of parallel nanostructure fabrication, lubricants for MEMS, corrosion protection and sensing. Thioethers are more resilient to oxidation than thiols and offer the potential for control over nanoscale assembly in two dimensions parallel to the surface. Low-temperature scanning tunneling microscopy (LT-STM) data demonstrates that thioethers form large, very well ordered domains with little or no defects that cover areas >1,000nm2. In contrast to alkane thiol assembly on the same surface, thioethers do not lift the Au {111} herringbone reconstruction. This feature facilitates defect-free thioether assembly which is not disrupted by etch-pit formation that alkane thiol SAMs suffer from. These data suggest the potential use of thioethers for a variety of self-assembly applications that require very perfect assembly and control over molecular spacing parallel to the surface.

Thioethers also constitute a simple, robust system with which molecular rotation can be actuated thermally, mechanically and electrically. By monitoring the rate of rotation as a function of tunneling electron energy (action spectroscopy) we have demonstrated that the rotors can be driven electrically via a mechanism that involves excitation of a C-H stretch. Forming ordered arrays of molecular rotors may provide entirely new approaches to signal processing, sensing, and energy modulation. For this application, an array of dibutyl sulfide rotors has been formed on a Ag/Cu{111} surface alloy. Molecular rotors can also act as standards by which scanning probe chirality can be measured and assigned. Such atomic-scale geometric data about the STM tip allows unambiguous chirality assignment on individual, isolated, molecule basis for the first time.

Palladium and its alloys play a central role in a wide variety of industrially important applications such as hydrogen reactions, separations, storage devices, and fuel cell components. The exact mechanisms by which many of these processes operate have yet to be discovered. LT-STM has been used to investigate the atomic-scale structure of Pd/Au and Pd/Cu bimetallics created by depositing Pd on both Au(111) and Cu(111) at a variety of surface temperatures. We demonstrate that individual Pd atoms in an inert Cu matrix are active for the dissociation of hydrogen and subsequent spillover onto Cu sites. Our results indicated that H spillover was facile on Pd/Cu at 400 K but that no H was found under the same H2 flux on a Pd/Au sample with identical atomic composition and geometry.