  The interface chemistry of silicon nanocrystals (NCs) embedded in amorphous
oxide matrix is studied through molecular dynamics simulations with the
chemical environment described by the reactive force field model. Our results
indicate that the Si NC-oxide interface is more involved than the previously
proposed schemes which were based on solely simple bridge or double bonds. We
identify different types of three-coordinated oxygen complexes, previously not
noted. The abundance and the charge distribution of each oxygen complex is
determined as a function of the NC size as well as the transitions among them.
The oxidation at the surface of NC induces tensile strain to Si-Si bonds which
become significant only around the interface, while the inner core remains
unstrained. Unlike many earlier reports on the interface structure, we do not
observe any double bonds. Furthermore, our simulations and analysis reveal that
the interface bond topology evolves among different oxygen bridges through
these three-coordinated oxygen complexes.
