Ordered Structure and Ion Migration in Silicon Dioxide Films

Abstract

Structure of silicon dioxide films thermally grown on silicon was studied with electron diffraction and the effect of impurities intentionally added during oxidation was examined. The local polycrystallization of SiO₂ films is enhanced by protons or boron atoms. Phosphor, on the contrary, suppresses the crystallization and antimony behaves in a similar way. Gallium has no influence on the phenomenon. Diffusion coefficient of sodium ions in these samples was also measured and activation energy for diffusion was obtained 1.0 to 1.4 eV which coincides well with those reported by other workers. These values are not affected by the presence of impurities or structural anomalies, but the diffusion coefficient itself is large where the crystallization is marked. Phosphor immoblized sodium ions and the diffusion of protons was observed instead. These effects of impurities can be explained considering their valency and sites they occupy in SiO₂ network.