My primary professional interest is in Condensed Matter Physics, which is another way to say that I study materials, crystals, and different phases of matter, typically at a very, very small scale. My work has taken me into several exciting sub fields within the discipline including magnetism, disorder, interfaces, boundaries, and crystals. The tools my collaborators and I typically work with include x-ray diffraction experiments and direct imaging of surfaces, structures and atoms with microscopy. I've been fortunate to work at some of the brightest x-ray sources in the world : the Advanced Photon Source at Argonne National Lab and the Advanced Light Source at Berkeley National Lab. I am currently a post-doctoral researcher at Argonne in the Materials Science Division.
However, my interests are not truly confined within condensed matter physics, nor necessarily within physics itself. I enjoy thinking about all sorts of questions as to the how, what, and why of Nature, even when I myself am merely a spectator in a particular subject. I suppose I just enjoy learning. I also participate, when possible, in science outreach efforts. I've particularly enjoyed answering questions for sites such as Newton : Ask a Scientist and Mad Scientist Network.
What happens at the surface of a material? At the boundary between materials, very unusual phenomena can occur. Very often the character of a surface can be quite different from the properties that exist throughout the rest of the material. At the same time, as things become smaller, the ratio of volume to surface decreases, and these effects become more and more important. This work is particularly important for the fields of electro-catalysis, nano-structures and magnetics. Our principle tools include both x-ray and electron diffraction experiments (an electron diffraction image is at left), as well as real imaging techniques from atomic and scanning tunneling microscopy. This combination of both real-space and reciprocal-space study has proven itself to be particularly powerful.
In particular, I’ve been working on projects to understand how the atomic arrangement of atoms at the surfaces of metals such as gold and platinum. Our group has been studying how these atoms respond to several different environmental properties including temperatures (all the way up to the bulk melting point) and how the atoms respond when different gases are introduced. We have been able to control the surface ordering and phases based upon different conditions never before observed. In particular we have been studying a gold surface in response in gases such as O2 and CO. The picture at left is a scanning tunneling microscope image showing long rows of gold atoms arranged along the surface steps.
One very exciting phenomena we are attempting to observe is how to cause a material to spontaneously facet in interesting ways. By creating an unstable arrangement on the surface it is sometimes possible to cause the atoms to rearrange or buckle into more energetically favorable positions. Often they create very tiny alternating facets in a semi ordered fashion. Depending upon the growth conditions (ie temperature, gas pressure/content, duration, etc... ) we are able to influence the faceting in particular ways. Hopefully this will eventually enable more controlled growth or engineering of nanoscale objects.
My thesis project at the University of Washington involved scattering coherent soft x-rays through thin magnetic films. We were able to measure some rather interesting memory properties of the films, ie the ability of a particular sample to have a reproducible microscopic magnetic domain configuration. We found that by deliberately introducing disorder it is possible to profoundly influence the magnetic character of the samples. In essence, the more disorder placed in the sample, the more likely it would "remember" its previous domain configuration and return to it. U.W. X-ray Scattering
I've been fortunate enough to participate in a proposal for a new Soft X-ray Free Electron Laser built by the University of Wisconsin and MIT. It's been great fun to "think big" about the kinds of science that would be possible when such a device is built. It has also been quite challenging to come up with solid enough ideas to support such a large proposal and reasons in favor of why such a facility for soft x-rays needs to be built.
Amateur Astronomy Fun
I really enjoy dragging a telescope out into the open and observing all the beautiful objects in the sky. A while ago, I built my own telescope for fun. This has been a great experience, both in terms of simply observing different objects in the night sky as well as my pet project to measure the speed of light using only Newtonian physics!
There has been a great deal of effort to simulate and model the behavior of magnetic domains (and indeed all kinds of systems in nature that have domains and boundaries). I have been interested in describing this behavior numerically, both through physical models as well as through non-traditional methods such as cellular automata. Until this point most of the simulations have been done as supporting work to my experimental studies. However, I'd like to eventually extend this into a substantial work in its own right.
Communicating with the public about science has always been very important to me. Being a post-doctoral researcher doesn't leave much time for outside activities, but one of the things I find most rewarding is talk with people. Often this means setting up my telescope outside for neighborhood kids (and adults) to come by and get a peak at what's above. I also enjoy answering questions on public science forums such as Newton : Ask a Scientist and Mad Scientist Network. To see the specific questions I've posted about go here and here.