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Homoepitaxial Sr1+xTiO3+δ films with -0.2 ≤ x ≤ 0.25 grown by reactive molecular-beam epitaxy on SrTiO3 (001) substrates have been studied by ultraviolet Raman spectroscopy. Non-stoichiometry for strontium- deficient compositions leads to the appearance of strong first-order Raman scattering at low temperatures, which decreases with increasing temperature and disappears at about 350 K. This indicates the appearance of a spontaneous polarization with a paraelectric-to-ferroelectric transition temperature above room temperature. Strontium-rich samples also show a strong first-order Raman signal, but the peaks are significantly broader and exhibit a less pronounced temperature dependence, indicating a stronger contribution of the disorder- activated mechanism in Raman scattering.

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This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Applied Physics Letters, published by American Institute of Physics. Copyright restrictions may apply. DOI: 10.1063/1.3499273

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