Wafer-Scale Fabrication of Uniform Few-Layer Hexagonal Boron Nitride Stacks for Memristor Applications.

Few-layer hexagonal boron nitride (hBN) is a promising two-dimensional dielectric for electronic and neuromorphic devices. However, its practical deployment is often hindered by the thickness nonuniformity of as-grown samples and by defects introduced during the transfer-stacking process of assembled samples. In particular, the influence of the initial hBN quality on the final stacked-film quality remains insufficiently understood. Here, we report a wafer-scale strategy for fabricating high-quality few-layer hBN based on ultraflat single-crystal hBN (USC-hBN) monolayers. Compared with transfer-stacked hBN grown on Cu foil (rough hBN), stacked few-layer USC-hBN shows a much lower surface roughness and a drastically reduced wrinkle density, indicating superior flatness and interfacial cleanliness. Furthermore, memristors fabricated from six-layer USC-hBN exhibit clearer resistive-switching behavior and a higher ON/OFF ratio than those based on rough hBN, owing to the more uniform surface/interface. These results demonstrate that source-material flatness is a critical determinant of transfer-stacked hBN quality and device performance. This work provides an effective route toward reliable integration of high-quality two-dimensional dielectric films.