Strain Screening by Mobile Oxygen Vacancies in Strontium Titanate

Small variations in the concentrations of oxygen vacancies in complex-oxide materials such as SrTiO$_{3}$ produce tremendous changes in physical properties such as the carrier density. Consequently, characterizing and controlling the oxygen vacancy concentration has become of interest both technologically and fundamentally. Recently, Freedman et al [1] calculated the elastic dipole tensor for several types of point defects in SrTiO$_{3}$ and showed that the appropriately averaged tensor for an oxygen vacancy is nearly traceless, providing a mechanism whereby highly mobile oxygen vacancies screen the elastic strain field. Here, we report detailed diffuse x-ray scattering measurements of bulk SrTiO$_{3}$ crystals prepared with controlled oxygen vacancy distributions under varying uniaxial stress states, demonstrating the traceless nature of the elastic dipole tensor, correlations between vacancies, and elastic strain screening. \\[4pt] [1] D.A. Freeman, et al, Phys. Rev. B \textbf{80}, 064108 (2009)