Simple Method to Obtain Large‐Size Single‐Crystalline Oxide Sheets

Synthetic techniques to prepare large‐size, flexible, and high‐quality single‐crystalline sheets of transition metal oxides are crucial to developing low‐energy consumption devices. One promising way is a lift‐off and transfer technique using a heterostructure of polymer supporting oxide and Sr₃Al₂O₆ (SAO) layers grown on a single‐crystalline substrate. By removing the water‐soluble SAO and the supporting layers, the oxide sheet is obtained. Although some ferroelectric flexible sheets are prepared by this method, a simpler method for obtaining large‐size sheets is required. Herein, a lift‐off and transfer method is proposed without a supporting layer. With this simple method, single‐crystalline SrRuO₃ and BaTiO₃ flexible sheets with a lateral size of a few millimeters are successfully prepared. The SrRuO₃ sheet exhibits high crystallinity and conductivity. Meanwhile, the ferroelectricity of the BaTiO₃ sheet is successfully observed via polarization hysteresis loop measurements. In addition to the simplicity, this method has low costs and the substrate is reusable. Accordingly, the proposed method could enhance the development of various kinds of large‐size functional oxide sheets.