A single-phase epitaxially grown ferroelectric perovskite nitride.

The integration of ferroelectrics with semiconductors is crucial for developing functional devices, such as field-effect transistors, tunnel junctions, and nonvolatile memories. However, the synthesis of high-quality single-crystalline ferroelectric nitride perovskites has been limited, hindering a comprehensive understanding of their switching dynamics. Here we report the synthesis and characterizations of epitaxial single-phase ferroelectric cerium tantalum nitride (CeTaN) on both oxides and semiconductors. The polar symmetry of CeTaN was confirmed by observing the atomic displacement of central ions relative to the center of the TaN octahedra, as well as through optical second harmonic generation. We observed switchable ferroelectric domains using piezoresponse force microscopy, complemented by the characterization of square-like polarization-electric field hysteresis loops. The remanent polarization of CeTaN reaches approximately 20 microcoulomb per square centimeter at room temperature, consistent with theoretical calculations. This work establishes a vital link between ferroelectric nitride perovskites and their practical applications, paving the way for next-generation information and energy storage devices.