Control And Regulation Of Phase Transition And Physical Properties In SrCoO_3-? Thin Films By Electrochemical Reaction

Transition metal oxides have been studied for a couple of years due to their peculiar electrical properties,magnetic properties and promising applications.Oxygen vacancy,a kind of defects commonly occurring in oxides,can significantly affect the properties of these materials,particularly the ordered ones.Many researchers employed varieties of methods to manipulate the concentration of oxygen vacancy in oxides,such as doping,strain engineering,post treating,ions gating and so on.Here,we proposed a method utilizing electrochemical reaction to adjust the oxygen content and phase transition in SrCoO_3-??SCO?thin films.The high-quality brownmillerite-like structure SrCoO_3-??BM-SCO?thin films studied in this study were deposited on SrTiO₃?STO?substrates by pulsed laser deposition?PLD?.The optimized growth parameters are as follows:the energy density of laser is 1.7 J/cm²;frequency of pulsed laser is 6Hz;the distance between target and substrate is 5 cm;the temperature of substrate is 800?;the oxygen pressure is 13 Pa;the growth time is 200 seconds.The phase transition was achieved by electrochemical reaction driving while being observed in-situ by X-ray diffraction?XRD?.It is shown that SCO can be switched continuously by either step or constant applied electric field.The phase transition between brownmillerite SrCoO_3-?and perovskite SrCoO_3-??P-SCO?can be completed in less than2 minutes.The resistivity,magnetization and optical transmittance of thin film were measured during the phase transition process.The resistance of an as-deposited BM-SCO thin film is 2 M?,while it fell to 2 K?when the film was transformed to P-SCO.The antiferromagnetic BM-SCO was transformed to ferromagnetic P-SCO,and the saturation magnetization reaches 100 emu/cm³ from near-zero with a transition temperature T_c at²02K.The infrared light optical transmittance of the SCO films can be changed between30%and 98%and the visible light transmittance is ranging from 30% to 80%.