Positron annihilation states at SiO₂/Si interfaces: Evidence of divacancies

We present a method based on positron annihilation to investigate defects at interfaces formed between a thin 10-50 Å overlayer and a substrate. The method applied to 38 SiO₂/Si interfaces gives evidence that (i) high concentrations of divacancies exist in Si domains at the interfaces formed with natural oxides obtained after etching and that (ii) positrons see the same annihilation state at various SiO₂/Si interfaces where the oxides are either commercial, thermally grown, native or obtained after rapid thermal annealing treatments.