Study of oxygen vacancies in SrTiO3 by positron annihilation

Oxygen vacancies introduced by homoepitaxial growth of thin films on strontium titanate (SrTiO3) substrates were studied by means of positron annihilation. The SrTiO3 films were grown by molecular-beam epitaxy without using an oxidant. The Doppler broadening spectra of the annihilation radiation wer...

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Veröffentlicht in:Journal of applied physics 2002-09, Vol.92 (5), p.2697-2702
Hauptverfasser: Uedono, Akira, Shimayama, Kazuo, Kiyohara, Masahiro, Chen, Zhi Quan, Yamabe, Kikuo
Format: Artikel
Sprache:eng
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Zusammenfassung:Oxygen vacancies introduced by homoepitaxial growth of thin films on strontium titanate (SrTiO3) substrates were studied by means of positron annihilation. The SrTiO3 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 incident positron energy for the SrTiO3/SrTiO3 samples fabricated by various growth conditions. The line shape parameter S, corresponding to the annihilation of positrons in the substrate, was found to be increased by the growth of the film. This increase was attributed to the diffusion of oxygen from the substrate into the film, and the resultant introduction of oxygen vacancies in the substrate. Two different types of defects in the substrate were identified: one is oxygen multivacancies, such as oxygen divacancies, and the other is their complexes with Sr vacancies. The concentration of oxygen vacancies in the subsurface region increased as the substrate temperature during the growth decreased (⩽320 °C). This fact was attributed to the decrease in the diffusion length of oxygen at low temperatures, and the resultant accumulation of oxygen vacancies in the subsurface region.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1498889