Review of the Fabrication of SrFeO_2.5 Thin Film and Its Functionalities

Brownmillerite transition metal oxides are materials with alternating layers of transition metal–oxygen octahedral (MO6) and transition metal–oxygen tetrahedral (MO4), which have attracted considerable attention because of their various physical properties, for example, ion conductors, catalysts, synaptic device properties, metal-insulator transition, and multiferroicity. In particular, we can easily control the structure of the SrFeO2.5 thin film through pulsed laser epitaxy conditions and heat treatment. In this paper, we will discuss the fabrication and properties of SrFeO2.5 thin films deposited using pulsed laser epitaxy. The developmental trend of SrFeO2.5 thin-film devices based on topotactic phase transition and the behavior of atoms will be examined to promote oxygen diffusion during the topotactic phase transition. Furthermore, the room-temperature ferroelectric and ferromagnetic phenomena utilizing the low-dimensional tetrahedral network within the brownmillerite structure will be discussed.