Nanocrystals and atomic layer deposition (ALD).
Nanocrystals are small crystalline particles of condensed matter with a characteristic size on the order of 1 billionth of a meter. Nanocrystals have very large surface-area-to-volume ratio. In fact, as much as 50% of the atoms in a nanocrystal may reside at the surface. As a result, interfaces play a central role, and the behavior of these small bits of matter can be dramatically different compared to bulk materials with the same chemical composition. We make use of atomic layer deposition, which is a conformal thin film deposition method with angstrom-level control over thickness, to tailor the surfaces of nanocrystals.
Electron transport in assemblies of nanocrystals.
Nanocrystals are being explored for a variety of optoelectronic applications in which electron transport is critical to performance. And yet, structure-property relationships are not understood at a level that allows design of the material to achieve a desired outcome. We are interested in developing such structure-property relationships to allow nanostructure to be designed to meet the needs of various optoelectronic applications.
Nanocrystals also present an opportunity to study collective effects and emergence. Since nanocrystals have such small size, a typical thin film sample may contain as many as 100 trillion particles. We are interested in understanding how electrons are transported at the mesoscopic scale through the network comprised of nanocrystals. Preliminary evidence suggests it is different from our intuitive expectations.
Low temperature plasmas for the processing of materials.
Low temperature plasmas are partially ionized gases that may contain suspended particles of condensed matter. In nonthermal plasma, the neutral gas molecules and ions are relatively cool (near room temperature), but free electrons are very hot with kinetic energy from 1 to 10 eV. These hot electrons can promote chemical reactions at high rates despite the low gas temperature. Particles suspended in the plasma experience intense ion bombardment, which is a unique feature of dusty plasma that we are exploring for material processing.
The high balance-of-systems costs for photovoltaic panels necessitates that solar cells must have high energy conversion efficiency and long-term stability. For this reason, our focus is on manufacturing innovation for established high performance materials such as silicon and GaAs. We focus on understanding the fundamentals of new processes that are viable alternatives to the important steps in established manufacturing approaches..