Structural Defects and the Origin of the Second Length Scale inSrTiO3

To understand the origin of the second long-length scale in $\mathrm{SrTiO}{}_{3}$, we studied structural defects in Verneuil-grown single crystals by transmission electron microscopy. The density of the dislocations was observed to decrease with increasing depth from the original cut surface of the crystals. The high density of dislocations in the skin region is most likely responsible for the second length scale.