 In this study, researchers have discovered that strain-free, freestanding two-dimensional strontium titanate, SRTIO3, membranes exhibit spontaneous out-of-plane polarization when subjected to an electric field. This phenomenon was attributed to the presence of oxygen vacancies in the lattice structure of the membrane, which were caused by the strain-free nature of the membrane. These findings suggest that the spontaneous polarization in these membranes can be further enhanced by applying an electric field, opening up new possibilities for applications in logic and memory devices. This article was authored by Yuying Zhang, Jimmingly, Kuyang, and others.