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The annealing behaviors of oxygen vacancies introduced by the epitaxial growth of thin SrTiO3 and Al2O3 films on SrTiO3 substrates were studied by using a monoenergetic positron beam. The films were grown by molecular-beam epitaxy without using an oxidant. The Doppler broadening spectra of the annihilation radiation were measured as a function of the incident positron energy for samples fabricated under various growth conditions. The line-shape parameter S, corresponding to the annihilation of positrons in the substrate, was increased by the film growth, suggesting diffusion of oxygen from the substrate into the film and a resultant introduction of vacancies (mainly oxygen vacancies). A clear correlation between the value of S and the substrate conductivity was obtained. From isochronal annealing experiments, the Al2O3 thin film was found to suppress the penetration of oxygen from the atmosphere for annealing temperatures below 600 °C. Degradation of the film’s oxygen blocking property occurred due to the annealing at 700 °C, and this was attributed to the oxidation of the Al2O3 by the atmosphere and the resultant introduction of vacancy-type defects. [ABSTRACT FROM AUTHOR]

Vacancy-type defects in the CeO[sub 2]/SrTiO[sub 3] structure were studied by means of positron annihilation. Thin CeO[sub 2] films were grown on SrTiO[sub 3] substrates by molecular-beam epitaxy without using an oxidant; oxygen was supplied by diffusion from the substrate (this process is referred to as automatic feeding epitaxy). A preferential epitaxial growth of CeO[sub 2](001) on SrTiO[sub 3](001) was observed, but an increase in the film thickness or annealing in an O[sub 2] atmosphere caused a partial growth of CeO[sub 2](110). The introduction of this phase was found to correlate with the reduction in the concentration of vacancy-type defects. The species of defects introduced into the SrTiO[sub 3] substrate was found to be not only oxygen vacancies but also Sr vacancies or their complexes. We discuss the mechanism that introduced cation vacancies in terms of oxygen nonstoichiometry. We found the trapping rate of positrons by Sr vacancies to depend on the sample temperature. This was associated with the temperature dependence of the dielectric constant near the defects or the presence of shallow trapping centers. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Vacancy-type defects in CeO2/SrTiO3 structure are studied using positron annihilation. The findings show that the value of the S parameter corresponding to the annihilation of positrons in the SrTiO2 substrate is increased by the formation of the CeO2 film.