Structure Simulation on Twisted Boundaries in SrTiO3 Bicrystals by Molecular Dynamics Calculation

Bicrystals of SrTiO3 with twisted boundaries were prepared by a HIP method and were observed with a transmission electron microscope (TEM). The bicrystals exhibited different nonlinear current-voltage characteristics depending on twist angle. A Molecular dynamics calculation was applied in order to understand the detailed interface structure. The periodicity of the Σ5 twisted boundary was calculated to be 1.58 times longer than the lattice constant of SrTiO3 along the (130) axis, and agreed with the periodicity observed by TEM, i.e., 1.57. Coincidence sites formed between Ti ions of the TiO2 layer and O ions of the SrO layer at the interface and did not shift the positions predicted by a coincidence sites lattice model; such coincidence sites caused the structural periodicity along the interface.