Extended Defect Control in Stannate Perovskite Oxide Thin Films Using Nanoscale Patterning

Stannate perovskite oxides like BaSnO₃ and SrSnO₃ are known to have a wide-range of extended defects in their structures, introducing unique and desirable properties for application in devices. Hence, understanding the origins of their formation and methods to control defect concentration are important. In this work, we use nanoscale patterning of the substrate surface, SrTiO₃ using a Ga ion beam in a focused ion beam instrument, to create localized atomic-scale roughness for controlling defect nucleation. By adjusting the Ga ion-beam doses, different surface structures are created onto the substrate, which is utilized in the growth of SrSnO₃ and La: BaSnO₃ thin films by hybrid molecular beam epitaxy (MBE). X-ray diffraction and scanning electron microscopy (SEM) of the films after growth show in both cases, films are epitaxial, high-quality and grow over the ion-beam modified areas of the substrate. Atomic structure of the films in the patterned areas are studied using analytical scanning transmission electron microscopy (STEM), which reveals: (i) planar Ruddlesden Popper type of faults present in the SrSnO₃ growing in the patterned channels with a five-fold higher density when compared to the bulk defect free film, and (ii) four-fold higher concentration of line defects, namely single and dissociated dislocations in the case for La: BaSnO₃, thus demonstrating the use of this method to control defect growth.