Defect engineering in BaSnO₃ and SrSnO₃ thin films through nanoscale substrate patterning

Creating 1D or 2D extended defects in thin films that propagate throughout the film thickness enables engineering nanoscale materials with anisotropic properties governed by these defects. Performing defect engineering of thin films with location specificity facilitates new nanoscale device architectures that harness the unique properties of these anisotropic extended defects. Here we demonstrate that, by combining Ga focused ion-beam (FIB) exposure and subsequent heat treatment, it is possible to pattern nanoscale structural perturbations on the substrate surface that promote nucleation and propagation of extended defects in thin films epitaxially grown on these substrates. Using SrTiO₃ as a substrate for growing perovskite BaSnO₃ and SrSnO₃ thin films, we demonstrate engineering ultra-high densities of threading 1D dislocations and 2D Ruddlesden-Popper faults with nanometer-level location specificity limited only by the resolution of the patterning Ga ion-beam of the FIB. Given the versatility of this method, it can be applied to different substrates and films, serving as a flexible means of defect-driven material engineering.