Role of interface suboxide Si atoms on the electronic properties of Si/SiO2 superlattices

Silicon/SiO2 superlattices (SLs) are nanostructured thin films bearing multiple Si/SiO2 interfaces. In such materials, silicon is walled by its oxide in order to generate multiple quantum wells. Here, the structural and electronic properties of a structurally-relaxed Si/SiO2 SL model are studied using a first principles approach; the Si/SiO2 interfaces contain all suboxide Si atoms (Si1+, Si2+, and Si3+). The valence and conduction band offsets (VBO and CBO) are evaluated from the relative shift between densities of states (DOSs) of Si atoms in bulk SiO2 and in the SL. The CBO is shown to be reduced compared to the VBO. The DOSs of the three suboxide Si atoms are also calculated. It is shown that there are contributions from all suboxides at the threshold of the gap