Perovskite-Derived Layered Crystal Structure in SrCo_0.26Fe_0.74O_3- Thin Films

Oxygen coordination and vacancy ordering play an important role in dictating the functionality of complex oxides. In this work, an unconventional layering of oxygen ions in a mixed conductor SrCo1-xFexO3-delta (SCFO) thin film grown epitaxially on SrTiO3 (STO) is reported. Scanning transmission electron microscopy (STEM) reveals alternating layers of oxygen deficiency along the growth direction, with the oxygen-rich layer correlated with the neighboring Co,Fe-site intensity, and contraction of the Sr-Sr distance. Density functional theory (DFT) calculations and STEM image simulations support the emergence of periodic (Co,Fe)O-6 and (Co,Fe)O-4/(Co,Fe)O-5 layers, an ordering that is also sensitive to the Co:Fe ratio.