A density functional study of oxygen migration processes for silicon quantum dots.

The migration kinetics of oxygen inserted into the surface back-bond network of hydrogen terminated silicon quantum dots has been examined. Diffusion both inward and lateral to the surface have been modeled. We find activation energies for migration generally far exceed the thermal energy available at room temperature, and thermodynamically the production of sub-surface oxygen is not favored. Surface dangling bonds significantly affect migration barriers, stabilize sub-surface three-fold-coordination of oxygen and surface bridging structures that red shift the onset of optical transitions. We also show that ionization enhances oxygen migration of a fully passivated dot, but does not favor sub-surface oxygen.