Hexagonal boron nitride (h-BN), an isomorph of graphene, has attracted great attention owing to its potential applications as an ultra-flat substrate or gate dielectric layer in novel graphene-based devices. Besides, h-BN appears to be a promising material for deep ultraviolet (DUV) optoelectronic applications because of its extraordinary physical properties, such as wide band gap and high absorption coefficient. In this work, two-dimensional h-BN with controllable layers was synthesized on Cu foils by ion beam sputtering deposition, and DUV photodetectors were fabricated from the transferred h-BN layers on SiO/Si substrates. The h-BN layers synthesized at the higher substrate temperature possess a lower density of domain boundaries and higher crystalline quality, and the photodetectors based on a 3 nm h-BN layer exhibited high performance with an on/off ratio of >10 under DUV light illumination at 212 nm and a cutoff wavelength at around 225 nm. This work demonstrates that two-dimensional h-BN layers are promising for the construction of high-performance solar-blind photodetectors.

Atomically thin hexagonal boron nitride (h-BN) is gaining significant attention for many applications such as a dielectric layer or substrate for graphene-based devices. For these applications, synthesis of high-quality and large-area h-BN layers with few defects is strongly desirable. In this work, the aligned growth of millimeter-size single-crystal h-BN domains on epitaxial Ni (111)/sapphire substrates by ion beam sputtering deposition is demonstrated. Under the optimized growth conditions, single-crystal h-BN domains up to 0.6 mm in edge length are obtained, the largest reported to date. The formation of large-size h-BN domains results mainly from the reduced Ni-grain boundaries and the improved crystallinity of Ni film. Furthermore, the h-BN domains show well-aligned orientation and excellent dielectric properties. In addition, the sapphire substrates can be repeatedly used with almost no limit. This work provides an effective approach for synthesizing large-scale high-quality h-BN layers for electronic applications.