First-principles study of migration, restructuring, and dissociation energies of oxygen complexes in silicon

Abstract

Migration, restructuring, and dissociation energies of oxygen complexes in silicon are studied theoretically through density-functional total-energy calculations. We find that the stablest oxygen complexes are straight chains that also have the lowest migration energies. The calculated migration energies decrease from 2.3 eV for an interstitial oxygen atom $({\mathrm{O}}_{i})$ to low values of 0.4--1.6 eV for ${\mathrm{O}}_{2}--{\mathrm{O}}_{9}$ chains and 1.9--2.2 eV for longer chains. The oxygen chains (which are thermal double donors) are expected to grow so that the migrating oxygen chains capture less-mobile but abundant ${\mathrm{O}}_{i}'\mathrm{s}:$ ${\mathrm{O}}_{n}+{\mathrm{O}}_{i}\ensuremath{\rightarrow}{\mathrm{O}}_{n+1}.$ Restructuring energies of chains with a side ${\mathrm{O}}_{i}$ into straight oxygen chains are $1.9--2.5 \mathrm{eV}.$ Restructuring gives an essential contribution to the fast diffusion. We find that the shorter ${\mathrm{O}}_{2}--{\mathrm{O}}_{9}$ chains dissociate primarily by ejecting one of the outermost oxygen atoms.