I’m back in Richmond now, having just returned from a year-long research sabbatical in France working on a new project involving “Black Silicon.” When a smooth surface of pure silicon is subjected to plasma etching under certain special conditions, it can spontaneously form a dense forest of microscopic spikes and holes, typically a few hundred nanometers across and a handful of microns high. As a result of this extreme roughness, light which is incident on the surface becomes trapped, and is eventually absorbed by the material, making it appear black to the naked eye. Beyond the many interesting physics questions this material raises (How does this happen? What determines the length scale?) this material has several potential applications, including the possibility for more efficient solar cells.
My work in France was at ESIEE Paris, an engineering school in the eastern suburbs of Paris. I will continue to work on this project here at Richmond, collaborating with my French colleagues remotely. Although we don’t have the plasma etching equipment here, we do have access to microscopy and analysis tools. I also expect to return to Paris for several weeks at a time during the summers.