Silicon interstitials at Si SiO2 interfaces: Density functional calculations

Using density functional theory calculations within the generalized gradient approximation, we have examined the behavior of single Si interstitials in the vicinity of Si SiO2 interfaces. We have identified three stable interstitial configurations at the interfaces, including (111)-split, Si2+-O bond centered, and Si4+-O bond centered. The interface interstitials turn out to be substantially more stable than bulk interstitials in Si, mainly due to bond formation with neighboring lattice Si and/or O atoms. We have calculated the diffusion of interstitials from Si to the Si SiO2 interface, showing the ease of the interface stabilization with no sizable barrier. We also discuss the migration of Si interstitials into the SiO2 layer at the c-Si c-SiO2 and c-Si a-2 interfaces.