Positron annihilation on the surfaces of SiO2 films thermally grown on single crystal of Cz–Si

Abstract

Two-detector coincidence system and mono-energetic slow positron beam has been applied to measure the Doppler broadening spectra for single crystals of SiO2, SiO2 films with different thickness thermally grown on single crystal of Cz–Si, and single crystal of Si without oxide film. Oxygen is recognized as a peak at about 11.85×10−3m0c on the ratio curves. The S parameters decrease with the increase of positron implantation energy for the single crystal of SiO2 and Si without oxide film. However, for the thermally grown SiO2–Si sample, the S parameters in near surface of the sample increase with positron implantation energy. It is due to the formation of silicon oxide at the surface, which lead to lower S value. S and W parameters vary with positron implantation depth indicate that the SiO2–Si system consist of a surface layer, a SiO2 layer, a SiO2–Si interface layer and a semi-infinite Si substrate.