Robust Nanocapacitors Based on Wafer-Scale Single-Crystal Hexagonal Boron Nitride Monolayer Films

Two-dimensional wafer-scale and single-crystal hexagonal boron nitride (h-BN) films are considered a crucial part of the next generation of van der Waals (vdW) electronic devices. Progress has been made in the synthesis process recently, leading to the demonstration of electronic devices. In this work, we report an effective method to synthesize high-quality single-crystal h-BN monolayer films. Single-crystal metal substrates were produced by thermal annealing of Ni foils, followed by electropolishing to remove the passivated surface layer. Molecular beam epitaxy was employed to synthesize 1 in.2 monolayer single-crystal h-BN films. We discovered that electropolishing plays an important role in drastically increasing the speed of h-BN film growth. Robust nanocapacitors were fabricated using as-grown monolayer h-BN films. The nanocapacitance effect and tunneling current mechanism were studied in detail, and the “effective distance” concept is introduced to explain the quantum phenomenon in the (vdW) metal–insulator–metal devices using atomically thin dielectric h-BN films.