Epitaxial integration of tetragonal BiFeO3 with silicon for nonvolatile memory applications

Ferroelectric field-effect transistor has long been considered as a promising nonvolatile memory technology, but its application is limited by the poor scalability. Here we show that this problem can be solved by epitaxially integrating tetragonal BiFeO3, a stress-induced metastable phase which exhibits remarkably low dielectric permittivity and high coercive field, on the silicon platform. Tetragonal BiFeO3 was stabilized on (001)-oriented silicon by using Bi2SiO5, which is chemically and structurally compatible with both silicon and tetragonal BiFeO3, as the buffer layer. Unlike the commonly observed M-C structure, the obtained BiFeO3 layer exhibits a true tetragonal symmetry. An unprecedented high memory window of 6.5 V was observed for the Au/BiFeO3/Bi2SiO5/Si capacitor with BiFeO3 thickness of 135 nm. The epitaxial integration of tetragonal BiFeO3 with silicon may pave a possible avenue for nanosized, power-efficient ferroelectric nonvolatile memories.