CHARACTERIZATION OF SIO2-FILMS GROWN ON SI SUBSTRATES BY MONOENERGETIC POSITRON BEAMS

Variable-energy positron beams were utilized to characterize SiO2 films grown on Si substrates. For a SiO2 film grown by wet oxidation, a high formation probability of positronium (Ps) was found by measurements of Doppler broadening profiles of the annihilation radiation and those of lifetime spectra. For the SiO2 films grown by a chemical vapor deposition technique, the formation probability of Ps was found to decrease. This was attributed to interactions between positrons and -OH bonds and to the trapping of positrons by point defects. In order to know annihilation characteristics of Ps in the SiO2 films in more detail, a lifetime spectrum for a vitreous silica glass was also measured.