Below you can find descriptions of the research projects that are currently going on in our group. Surface Science is a wide field, and there are many topics that intersect in some way or another with our main interests. Smaller side projects often spring from our need to gain a better understanding of a particular item.

I. Mechanisms of Nanoscale Pattern Formation during Electropolishing

Nanoscale surface patterning is of great importance for applications ranging from catalysts to biomaterials. We have shown the formation of ordered nanoscale dimple arrays on tantalum, titanium, tungsten and zirconium during electropolishing. This is a rare example of an electrochemical pattern formation process that can be translated to other materials. The dimpled surfaces have been characterized with a variety of techniques including scanning electron microscopy, transmission electron microscopy, atomic force microscopy, nuclear reaction analysis and x-ray photoelectron spectroscopy. The electrochemical conditions were optimized for each material. While conditions for titanium and tungsten resemble those for tantalum, zirconium requires a different type of electrolyte. Given the appropriate electropolishing chemistry, formation of these patterns should be possible on any metal surface. The process is very robust on homogeneous surfaces, but sensitive to inhomogeneities in chemical composition, such as in the case of differentially etched alloys. Of particular interest are the understanding of the underlying mechanism (selective oxide growth or dynamics of the liquid phase) and possible extensions to other materials systems.

II. Atomic and Molecular Mobility at Interfaces

We like to think of surfaces and interfaces as static and stable systems, but even the gold atoms at the surface of that ring on your finger are far from settled into place. Surface diffusion at clean gold surfaces has been documented at just a few degrees above room temperature, and adsorbates only make the gold atoms more mobile. Surface diffusion of a range of organic molecules on silica has been frequently reported in the past as well. Now, this behavior can be a major nuisance if you are trying to make a stable organic electronic device or improve the resolution of your chromatographic column. But it is also an opportunity if you are interested in nanostructuring of surfaces, certain types of chromatography, drug delivery or self-healing protective coatings. We are studying the mobility of atomic and molecular species at a variety of surfaces with a range of applications.