Nonstoichiometric [012] dislocation in strontium titanate

Dislocations are one-dimensional lattice defects in crystalline materials, and unique atomic configurations at their core can affect functional properties of materials. Here we report on a [012] dislocation having a nonstoichiometric core structure in strontium titanate (SrTiO3). TEM and STEM observations showed that a (001) low-angle tilt grain boundary consists of two types of dislocations. One is a [001] edge dislocation that compensates a tilt angle of the boundary as found in previous studies. The other is a [012] dislocation with both edge and screw component. This dislocation is considered to be formed to compensate a slight twist angle of the boundary. It is interesting that the [012] dislocations have a specific core structure with the dissociation into three partial dislocations of b = 1/2 [011], [001] and 1/2 [011]. At stacking faults formed with the dissociation, two (001) Ti-O layers were located to be neighbors across the stacking fault plane due to missing of a (001) Sr-O layer. In addition, the energy of the stacking fault was estimated to be 0.4 J/m2 from the separation distances between partial dislocations. It is suggested that the [012] dislocation is formed due to presence of the nonstoichiometric stacking fault structure with low energy.

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