  Oxidation of SiC produces SiO2 while CO is released. A `reoxidation' step at
lower temperatures is, however, necessary to produce high-quality SiO2. This
step is believed to cleanse the oxide of residual C without further oxidation
of the SiC substrate. We report first-principles calculations that describe the
nucleation and growth of O-deficient C clusters in SiO2 under oxidation
conditions, fed by the production of CO at the advancing interface, and their
gradual dissolution by the supply of O under reoxidation conditions. We predict
that both CO and CO2 are released during both steps.
