Lattice relaxations around individual dopant atoms in SrTiO3

The local atomic structure around individual dopant atoms can directly influence the electronic properties of a doped material. Here, we use quantitative scanning transmission electron microscopy to study the local lattice relaxations around Sm dopant atoms in SrTiO3 thin films. These films have recently been shown to undergo successive ferroelectric and superconducting transitions when strained. We show that neighboring Ti-O columns move away from the columns that contain Sm dopants. The observed displacements are, however, more complex than a simple outward expansion of all four surrounding Ti-O columns. We discuss potential implications, especially for the ferroelectric transition observed in strained films.