By controlling the synthesis and process conditions, we show that the oxygen vacancy channels (OVCs) of Brownmillerite-structured SrFeO2.5+? (0=??0.5) thin films can be oriented differently on the same LaAlO3(001) substrate due to either a bottom up or top down synthesis route. The brownmillerite structure formation and evolution processes yield distinctively different optical and electronic properties, owing to the difference in the oxygen content and OVC configuration in the resultant films. Moreover, we also show that in situ transmission electron microscopy (TEM) can induce oxygen loss and drive a phase transition from perovskite SrFeO3 to brownmillerite SrFeO2.5+? with mixed horizontally and vertically aligned OVCs. The dimensionality change during the TEM sample preparation makes the bottom up and top down model not applicable. Our results offer further insight into the phase stability and oxygen-diffusion mechanisms, which is important for the predictive synthesis of novel functional materials.
Revised: April 9, 2020 |
Published: June 10, 2019
Citation
Wang L., Z. Yang, M.E. Bowden, and Y. Du. 2019.Brownmillerite Phase Formation and Evolution in Epitaxial Strontium Ferrite Heterostructures.Applied Physics Letters 114, no. 23:Article No. 231602.PNNL-SA-141379.doi:10.1063/1.5096769