Epitaxial Growth of Aurivillius Bi₃Fe₂Mn₂O_x Supercell Thin Films on Silicon

Nanoelectronic devices integrated with functional complex oxides have drawn much attention in recent years. However, due to material and processing compatibility issues, integrating functional complex oxides with Si-based devices is challenging, and success has been limited. As an example, the Bi3Fe2Mn2Ox (BFMO) supercell system, a single-phase layered oxide made by compositing BiFeO3 and BiMnO3, has been studied for much of the past decade for its unusual layered Aurivillius structure and magnetic and ferroelectric properties. However, most of the BFMO thin film growth has been demonstrated on single-crystal oxide substrates such as SrTiO3 and LaAlO3. In this work, we demonstrate that the BFMO layered supercell phase can be integrated on Si with high epitaxial quality using a buffer stack of TiN/SrTiO3/CeO2. Further understanding of the strain-controlled growth of the BFMO supercell phase has allowed such Si integration. Microstructure, magnetic, ferroelectric, and optical properties of the BFMO films on Si have been characterized and compared with those of BFMO on SrTiO3 single-crystal substrates, demonstrating comparable epitaxial quality and physical properties. Integrating multiferroic BFMO oxides on Si demonstrates the potential of layered supercell oxides in practical device applications such as ferroelectric field effect transistors.