Self-Rolling-Up Enabled Ultrahigh-Density Information Storage in Freestanding Single-Crystalline Ferroic Oxide Films

Ferroelectric memory is one of the most attractive emerging nonvolatile memory. Conventional methods to increase storage density in ferroelectrics include reducing the storage bit size or fabricating 3D stacks. However, the former will face a physical limit finally, and the integration of single-crystalline ferroelectric oxide following the latter still remains a great challenge. Here, a new method is introduced to construct a scroll-like 3D memory structure by self-rolling-up single-crystalline ferroelectric oxides. PbZr_0.3Ti_0.7O₃ single-crystalline thin film is chosen as a prototype and epitaxially grown on another oxide stressor layer with a few lattice-mismatch. Releasing such “Pb(Zr, Ti)O₃/stressor” bilayered structure from the substrate induces self-rolling-up due to the internal stress from the lattice-mismatch. High-density information can be written in the form of switched ferroelectric domains on those flat “Pb(Zr, Ti)O₃/stressor” membranes via piezoelectric force microscopy. In self-rolling-up membranes, information density can be experimentally enhanced up to 45 times. Theoretically, the freestanding “Pb(Zr, Ti)O₃/stressor” membranes have a strongly driven force to self-rolling-up, and the area ratio can enhance 100–450 times, corresponding to an ultra-high density information storage of 10² Tbit In⁻². This study provides a new and general method to develop compact, high-density, and 3D memories from oxide materials.