Isolated Oxygen Vacancies in Strontium Titanate Shine Red: Optical Identification of Ti³⁺ Polarons


Oxide perovskites exhibit fascinating physical properties that identify them as key materials for the next generation of oxide-based functional electronic devices, as well as for catalysis and photochemistry applications. In strontium titanate, substantial efforts have been devoted to elucidate the role of oxygen vacancies and localized electronic states, such as polarons, on those properties. A new model is presented that assigns a definitive red luminescence signature at 2.0 eV to Ti3+ polarons trapped at isolated oxygen vacancies. This emission provides an unequivocal identification for the oxygen vacancies, which allows monitoring their creation and annealing by a variety of physio-chemical treatments. Ionoluminescence with energetic (MeV) ion beams enables such identification by combining the sensitivity and resolution of spectroscopic techniques with their in situ character, as well as controlled incorporation of point defects, such as oxygen vacancies. Alternative models assigning the blue luminescence emission at 2.8 eV to oxygen vacancies are not supported by the experimental results. Therefore, oxygen vacancies shine red and not blue, as previously proposed.


Nuclear Engineering and Radiation Science


This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. M.L.C. and J.T.G. acknowledge support from the University of Tennessee Governor's Chair program. M.L.C. acknowledges Dr. Jianqui Xi's contribution for performing calculation of electronic density of states shown in Fig. 1 .

Keywords and Phrases

Defects; Ionoluminescence; Oxygen vacancies; Polarons; Strontium titanate

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Article - Journal

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© 2018 Elsevier, All rights reserved.

Publication Date

01 Sep 2018