Regular Article – Atomic and Molecular Collisions
Effect of thermochemical treatments on laser-induced luminescence spectra from strontium titanate: comparison with swift ion-beam irradiation experiments
Centro de Microanálisis de Materiales, CMAM-UAM, 28049, Cantoblanco, Madrid, Spain
2 Department of Materials Science and Engineering, University of Tennessee, 37996, Knoxville, TN, USA
3 Department of Nuclear Engineering and Radiation Science, Missouri University of Science and Technology, 65409, Rolla, MO, USA
4 Materials Science and Technology Division, Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA
Accepted: 29 November 2021
Published online: 28 December 2021
Results recently reported on the effect of thermochemical treatments on the (He-Cd) laser-excited emission spectra of strontium titanate (STO) are re-analyzed here and compared with results obtained under ion-beam irradiation. Contributing bands centered at 2.4 eV and 2.8 eV, which appear under laser excitation, present intensities dependent upon previous thermal treatments in oxidizing (O2) or reducing atmosphere (H2). As a key result, the emission band centered at 2.8 eV is clearly enhanced in samples exposed to a reducing atmosphere. From a comparison with the ionoluminescence data, it is concluded that the laser-excited experiments can be rationalized within a framework developed from ion-beam excitation studies. In particular, the band at 2.8 eV, sometimes attributed to oxygen vacancies, behaves as expected for optical transitions from conduction-band (CB) states to the ground state level of the self-trapped exciton center. The band at 2.0 eV reported in ion-beam irradiated STO, and attributed to oxygen vacancies, is not observed in laser-excited crystals. As a consequence of our analysis, a consistent scheme of electronic energy levels and optical transitions can now be reliably offered for strontium titanate.
© The Author(s) 2021
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