A generalized synthesis method for freestanding multiferroic two-dimensional layered supercell oxide films via a sacrificial buffer layer

Multiferroics are an intriguing family of materials due to the simultaneous presence of two ferroic orderings, namely, ferroelectricity and ferromagnetism. They are scientifically and technologically important and have numerous potential applications, such as four-state logic memories and multiferroic tunneling junctions. However, the growth of epitaxial single-phase multiferroic thin films typically requires single crystalline oxide substrates, which hinders their future integration with Si-based devices. In this study, we report a generalized synthesis method that uses the polydimethylsiloxane (PDMS)-assisted wet-etching method with an Sr₃Al₂O₆ (SAO) sacrificial layer to transfer freestanding single-phase multiferroic Bi₂NiMnO₆ (BNMO) films from conventional SrTiO₃ (STO) substrates onto a Si wafer. The structures and properties of the films have been characterized before and after the transfer. These transferred films possess good multiferroic properties on Si wafers, indicating full compatibility with modern Si technology. This method can be generally applicable to other Bi-based multiferroic materials as well. Lastly, the original STO substrates after the transfer process have been recycled for preparing new batches of freestanding BNMO films, indicating a low-cost and sustainable method for manufacturing large-volume freestanding complex oxide thin films.