The effects of c-Si/a-SiO₂ interface atomic structure on its band alignment: an ab initio study

The crystalline-Si/amorphous-SiO₂ (c-Si/a-SiO₂) interface is an important system used in many applications. However, the question of how this interface band offset would be affected by the transition region thickness and its local atomic arrangement, has yet fully investigated. Here, by controlling the parameters of the classical Monte-Carlo bond switching algorithm, we have generated the atomic structures of the interfaces with various thickness, as well as containing Si at different oxidation states. Hybrid functional method, are used to calculate the electronic structure of the heterojunction. We find that although the systems with different thickness show quite different atomic structure near the transition region, the calculated band offset tends to be the same, unaffected by the detail interfacial structure. It is shown that our band offset calculation agrees well with the experimental measurements. When the reactive force field is used to generate the a-SiO₂ and the c-Si/a-SiO₂ interface, the band offset significantly deviates from the experimental values by about 1 eV.