Dillon Fong1,Qingteng Zhang1,Guoxiang Hu2,Vitalii Starchenko3,Gang Wan1,Eric Dufresne1,Yongqi Dong1,Huajun Liu4,Hua Zhou1,Hyoungjeen Jeen3,Kayahan Saritas3,Jaron Krogel3,Fernando Reboredo3,Ho Nyung Lee3,Alec Sandy1,Irene Almazan1,Panchapakesan Ganesh3
Argonne National Laboratory1,The City University of New York2,Oak Ridge National Laboratory3,Institute of Materials Research and Engineering, A*STAR4
Dillon Fong1,Qingteng Zhang1,Guoxiang Hu2,Vitalii Starchenko3,Gang Wan1,Eric Dufresne1,Yongqi Dong1,Huajun Liu4,Hua Zhou1,Hyoungjeen Jeen3,Kayahan Saritas3,Jaron Krogel3,Fernando Reboredo3,Ho Nyung Lee3,Alec Sandy1,Irene Almazan1,Panchapakesan Ganesh3
Argonne National Laboratory1,The City University of New York2,Oak Ridge National Laboratory3,Institute of Materials Research and Engineering, A*STAR4
The brownmillerite phase of strontium cobaltite (SrCoO<sub>2.5</sub>) is an insulating antiferromagnet while the perovskite phase (SrCoO<sub>3</sub>) is a ferromagnetic metal. Relatively small changes to the oxygen concentration can drive a reversible, topotactic phase transition, making SrCoO<sub>3-δ</sub> a material of interest for neuromorphic applications. While the redox behavior of such oxides has been the subject of considerable interest, much concerning the kinetics and dynamics of these materials remain unknown.<br/><br/>Utilizing in situ coherent X-ray scattering at the Advanced Photon Source, we monitored speckle from epitaxial SrCoO<sub>3-δ </sub>thin films grown on both SrTiO<sub>3</sub>(001) and (LaAlO<sub>3</sub>)<sub>0.3</sub>(Sr<sub>2</sub>TaAlO<sub>6</sub>)<sub>0.7</sub>(001) as oxygen was incorporated and evolved (switching the environment from O<sub>2</sub> to N<sub>2</sub>) to gain insight into the dynamics of oxygen-induced phase evolution in complex oxide materials. We found that the kinetics of the brownmillerite to the perovskite phase transition could be varied from tens of minutes to several hours over a small temperature range (300°C to 350°C), observing pronounced differences between the oxidation and reduction behaviors, the latter involving substantial incubation times to re-nucleate the brownmillerite phase. From X-ray photon correlation spectroscopy performed at the brownmillerite superlattice reflection, we find that the two-time correlation function differs greatly between the two different substrates. We will discuss the kinetics and dynamics of the oxygen ion / vacancy-ordering phase transition and the methods used to distinguish the different atomic and electronic mechanisms taking place.