High quality hexagonal boron nitride (h‐BN) thick films are indispensable for practical deep‐ultraviolet (DUV) photodetector applications. However, the controllable synthesis of h‐BN films in terms of thickness and crystallinity often requires high growth temperatures, tedious chemical precursors and, catalytic transition metal substrates, that will eventually hinder their applicability. In this work, the direct growth of h‐BN films with thickness of 50–500 nm on silicon(100), sapphire, and quartz substrates by ion beam assisted deposition at a lower temperature (≈500 °C) without employing extra catalysis is reported. The as‐synthesized h‐BN thick films are stoichiometric, smooth, and continuous without obvious pinholes and cracks, consisting of nanocrystalline domains on the dielectric substrates, distinct from those grown on metallic substrates. More intriguingly, the DUV photodetector fabricated from a 500 nm thick h‐BN film on quartz substrate exhibits high peak responsivity (0.5 A W−1) with a ultrahigh on/off ratio of >103 at 204 nm, a high rejection ratio (R204nm/R250nm > 103), a large specific detectivity (6.92 × 109 Jones), and a sharp cutoff wavelength at 218 nm. The work herein demonstrates the great potential of this form of h‐BN thick films toward the development of DUV photodetectors.

Protection of stainless steel from water, oxygen, and chloride ions is of crucial importance for diverse industrial fields; yet, it remains challenging to develop a proper solution with improved corrosion and oxidation resistance for long-term service durability. Here, we demonstrate the direct growth of hexagonal boron nitride (h-BN) nanofilms on the surface of stainless steel (ss304) by the magnetron sputtering method, serving as barrier coatings for protection in a corrosive environment. The obtained h-BN nanofilms are ∼200 nm in thickness, with a highly densified morphology, converting the hydrophilic surface of ss304 to a hydrophobic surface. These films exhibit excellent oxidation resistance at 600 °C in the atmosphere and enhanced anticorrosion performance as compared to the bare ss304. Moreover, they show robust and stable corrosion resistance when immersed in a 3.5 wt % NaCl electrolyte for over 10 weeks. The results suggest that the direct growth of h-BN nanofilms on ss304 holds great promise for corrosion inhibition and antioxidation of steel, therefore offering a feasible and effective route for long-term corrosion protection concerning practical applications of h-BN on industry-relevant surfaces.

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Effective doping of ultra-wide band gap semiconductors is of crucial importance, yet, remains challenging. Here, we report the enhancement of n-type conductivity of nanocrystalline hexagonal boron nitride (h-BN) films with simultaneous incorporation of Si and O while deposition by radio frequency (RF) magnetron sputtering method. The resultant h-BN films are of ~50 nm in thickness, containing nitrogen vacancy (VN) defects. Incorporation of O together with Si results in effective healing of VN defects and significantly reduces electric resistivity in h-BN thin films. X-ray photoelectron spectroscopy (XPS) results reveal that under B-rich condition, the substitutional O in VN bonding with B leads to the formation of Si-N, which thus plays an important role to the n-type conductivity in h-BN films. The temperature dependent electrical resistivity measurements of the Si/O co-doped h-BN films reveal two donor levels of 130 and 520 meV at room temperature and higher temperatures, respectively. The n-h-BN/p-Si heterojunctions demonstrate apparent rectification characteristics at room temperature, where the tunnelling behaviour dominates throughout the injection regimes due to the effective carrier doping. This work proposes an effective approach to enhance the n-type conductivity of h-BN thin films for future applications in electronics, optoelectronics and photovoltaics.