Atomic-scale studies of native point defect and nonstoichiometry in silicon oxynitride

The native point defects and mechanism of accommodating deviations from stoichiometry of Si2N2O crystal have been investigated using atomistic simulation techniques. This work firstly provides a reliable classical interatomic potential model derived from density functional theory calculations. The force-field parameters well reproduce the crystal structure, elastic stiffness, and dielectric constants of Si2N2O. It is expected that the force-field parameters are useful in future investigations on Si2N2O by molecular dynamic simulation. The calculated formation energies for native defects suggest that intrinsic disorder in stoichiometric Si2N2O is dominated by antisites and a degree of oxygen Frenkel defect may also exist in this system. In nonstoichiometric Si2N2O, the calculated reaction energies indicate that excess SiO2 or Si3N4 is most likely accommodated by the formation of antisite in the lattice. And we also find that SiO2 excess is energetically more favorable than Si3N4 surplus in Si2N2O.