Impact of defects on local optical dielectric properties of Si/SiO2 interfaces by layered capacitor modeling

We present a new method to investigate the local optical dielectric permittivity using layered capacitors. The method has been applied to study the optical dielectric constants of Si/SiO2 structures without defects, with dangling bonds, and with dangling bonds passivated by H. For each of the three structures, models composed of 5, 7, and 12 Si layers were studied, and the effect of the Si layer thickness was assessed. The different local optical dielectric constants in the adjacent Si interface region were obtained for the nine models, and the effect of the Si layer thickness, the bond lengths, and the oxidation states of Si at the interface were analyzed. The results showed that the local optical dielectric constant of the structure with dangling bonds in the region adjacent to the Si interface was larger than that of the structure with no defects; and the effect of the interface defect Si+1 on the dielectric constant is stronger than that of the Si layer thickness, and effect scope of Si+1 reached approximate 7 A in silicon region.