Achievement

IGERT Fellow Will Tipton has studied the energetics of defect formation in the semiconductor zinc-oxide (ZnO) which holds promise for many applications including next-generation solar cells. An understanding of the material's defects is crucial for controlling its electronic properties and engineering useful devices. Prior theoretical studies of this system relied on density functional theory (DFT); however, Tipton and coworkers showed that energies calculated in this way depend strongly on the choice of parameters, and that it is unknown which methodological choice, if any, is reliable. This discovery led to the application of a more accurate method, quantum Monte Carlo (QMC), to calculate the pertinent energies. These results are useful both for understanding the conductivity of ZnO and for evaluating the various computational methods. Preliminary results of this ongoing study were presented at the 2010 American Physical Society March Meeting.