Raman study of oxygen reduced and re-oxidized strontium titanate

Abstract

We report Raman study of oxygen reduced single crystal strontium titanate. Oxygen reduction leads to the appearance of the forbidden first-order Raman peaks, as well as spectral features attributed to the local vibrational modes associated with oxygen vacancies. This assignment is supported by ab initio calculations of phonon modes in $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ with introduced oxygen vacancies. Raman studies of re-oxidized samples show the same spectra as the initial single crystals. Comparison of Raman spectra of $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ thin films and reduced $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ single crystals demonstrates the importance of other factors such as polar grain boundaries in the lattice dynamical behavior of thin films.