Validity of the bond-energy picture for the energetics atSi−SiO2interfaces

Using a first-principles approach, we assess the validity of a picture for the energetics at $\mathrm{Si}-{\mathrm{SiO}}_2$ interfaces based on bond energies complemented with penalty energies for silicon atoms in intermediate oxidation states. By total-energy calculations on cluster models, we demonstrate that such penalty energies only depend on the composition of the first-neighbor shell of the silicon atoms and can thus be taken as additive contributions to the total energy. Considering oxygen incorporation processes in $\mathrm{Si}-{\mathrm{SiO}}_2$ interface models, we show that variations in the interface energy result from suboxide and strain contributions of comparable magnitude. Hence, simplified schemes for the energetics at $\mathrm{Si}-{\mathrm{SiO}}_2$ interfaces should account for both contributions with similar accuracy.