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We have shown that STM-tip-induced chain polymerization of 10,12-tricosadiynoic acid (TCDA) in a self-organized monolayer at the liquid-solid interface of TCDA on highly oriented pyrolytic graphite is possible. The oligomers thus produced started at the point where a voltage pulse was applied between the STM tip and the sample during a short period when the feedback condition was momentarily suspended (as it is for scanning tunneling spectroscopy). Polymerization probabilities depended upon the length of the applied voltage pulse and were generally higher for longer pulse widths in the 10-ms to 100-micros time scales, approaching unit probability for the former and decreasing quickly to a few tens of percent for the latter. The polymerization could be confined to certain nanometer-sized areas by using "molecule corrals,"and polymerization appeared to be governed by topochemical constraints. Polymerization across domain boundaries, or over molecule corral edges, was never observed in over approximately 150 observations. Due to the constant supply of nonpolymerized molecules from the covering solution, a dynamic exchange between molecules on the surface and in the solution was possible. This exchange occurred on a time scale that was comparable to the image acquisition time (approximately 10(1) s), and appeared to depend weakly upon the length of the desorbing oligomer. The desorption process was probably also influenced by interactions with the STM tip.

Etch pits on highly oriented pyrolytic graphite (HOPG) were used as templates for the formation of gold nanostructures, which were characterized using STM (scanning tunneling microscopy), AFM (atomic force microscopy), XPS (X-ray photoelectron spectroscopy) and TOF-SIMS (time-of-flight secondary ion mass spectrometry). Controlled production of defects on HOPG by ion bombardment leads to the formation of nanometer-size etch pits by thermal oxidation in a controlled fashion. Etch pits act as nucleation and growth sites for gold nanostructures and also play a role in fixing gold nanostructures in place for study by scanning probe techniques. Hexagonal-shaped, flat-topped, and other gold nanostructures were formed in multilayer etch pits. XPS showed that the atomic percentage of gold on a pitted HOPG surface was higher than that on an unpitted HOPG surface for the same amount of deposited gold after annealing at an elevated temperature, indicating that more HOPG surface area was covered by gold on pitted HOPG than on unpitted HOPG. XPS O 1s spectra showed that there are two chemical states of oxygen on gold-covered HOPG samples, corresponding to oxygen adsorbed on gold nanostructures and oxygen adsorbed on HOPG. Oxygen adsorbs molecularly onto surfaces of gold nanostructures, where the coverage of molecular oxygen on gold nanostructures is 0.25 ML for adsorption at room temperature and atmospheric pressure. In contrast, no oxygen adsorption was observed on the surface of a Au(111) single crystal as reported in the literature. This relatively high molecular oxygen coverage is explained by the small size (20−50 nm) of the gold nanostructures. Additionally, two-dimensional gold nanostructure arrays were produced by depositing gold onto pit-patterned HOPG surfaces. These patterned gold nanostructures on HOPG have potential applications in fields such as catalysis, sensors, and nanoelectronics.

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