Structure and energetics of c-Si∕a-SiO₂ systems: Planar interfaces and embedded Si nanocrystals

We use Monte Carlo simulations to study the properties of the interfaces between c-Si and a-SiO₂, more specifically planar interfaces and interfaces between a-SiO₂ and embedded Si nanocrystals (NCs). We find that the Si(111)∕a-SiO₂ interface with suboxide Si⁺¹ only has the lowest interfacial energy among the planar cases considered. We also find that embedded NCs smaller than ∼20 Å have even lower interfacial energy, suggesting that a faceted shape is favorable only for large NCs. No significant differences are observed between normal and twinned NCs, indicating that the experimentally observed stacking faults might result from the coalescence of small defect-free NCs.