Laser Induced Fast Topotactic Phase Transition in Freestanding Oxide Membranes

Materials exhibiting topotactic transitions offer unique opportunities for engineering phase‐dependent properties. Topotactic transitions between brownmillerite (BM) and perovskite (PV) oxides are potentially useful for memristive devices, electrochromic, and solid electrolyte applications. However, achieving fast and uniform topotactic phase transition simultaneously is challenging, limiting their applications. Here, fast and well‐controlled laser induced topotactic transitions are shown in freestanding SrCoO 2.5 crystalline membranes, significantly faster than conventional annealing or ionic liquid gating methods. The phase transition is identified by Raman spectroscopy, local conductive atomic force microscopy (CAFM), and confirmed by atomic scale scanning transmission electron microscope (STEM) studies. First‐principles calculations confirm that the strain‐free condition in freestanding oxide membranes is crucial for laser triggered topotactic phase transition. The phase transition induces a 6 times reduction in resistance and multilevel resistance controllable by varying the laser treatment area. The fast, direct laser writing technique works as a simple, scalable method for optically writable memory devices.