Single-crystal rhombohedral boron nitride wafers for integrated sliding ferroelectric memory

Two-dimensional rhombohedral boron nitride (rBN) has emerged as a promising sliding ferroelectric material for high-density, fast-speed and non-volatile memories. However, the batch production of ferroelectric rBN wafers has remained a critical challenge due to the thermodynamic instability of the rhombohedral phase and the inherent difficulties in maintaining consistent growth kinetics. Here we report a step-templated interfacial epitaxy strategy that enables the reproducible fabrication of 4-inch rBN wafers from nickel-boron films sputtered on the stepped sapphires. Comprehensive structural characterizations across multiple scales confirm the high phase purity and batch-to-batch consistent quality of produced rBN wafers. The intrinsic sliding ferroelectricity is verified in a unified ferroelectric field-effect transistor (FeFET), which exhibits ultrafast switching speed (at the nanosecond scale), high fatigue resistance (>2 × 10⁹ cycles) and long-term non-volatility (10 years). FeFET arrays are also constructed based on rBN wafers, featuring a high integration density with significant on/off ratios (10⁶). Remarkably, the rBN FeFETs can maintain large memory windows (4 V) and excellent thermal stability (>470 K), even at an ultrashort channel length of 30 nm. These results establish rBN as a scalable platform for next-generation sliding ferroelectric memories, facilitating their applications in high-density memory chips and artificial intelligence accelerators.