A film stripping method that allows for liquid phase exfoliation assisted by spin coating polymethyl methacrylate has been investigated, resulting in a two‐inch hexagonal boron nitride (hBN) film to be fully stripped and then transferred. A number of key factors that can influence the stripping and the transferring process of the films grown by sputtering have been systematically analyzed, including different solutions, different concentration of solution and different thickness of films. The morphology and properties of the hBN films before and after stripping have been characterized. The band edge absorption peak of the transferred film is 229 nm and the corresponding optical band gap is 5.50 eV. Such transferred hBN films have been fabricated into transparent resistive switching devices on indium‐tin‐oxide glass, demonstrating a constant resistance window of ≈102 even under different applied voltages. This work systematically studies the stripping process, characterizes the transferred films, and explores the application in the field of resistance switching, which lay a foundation for the further application of hBN materials in optoelectronic devices.

Hexagonal boron nitride (h-BN) exhibits a dangling bond-free layered structure and ultrawide band gap, which is apt to integrate with other semiconductors to form a heterojunction. Particularly, heterojunction structure is the main impetus for h-BN to broaden the horizon on deep ultraviolet optoelectronic and photovoltaic applications. Here, a series of h-BN/B 1−x Al x N heterojunctions with different Al components were fabricated by radio frequency (RF) magnetron sputtering. The performance of h-BN/B 1−x Al x N heterojunction was measured via I−V characteristic representation. The sample of h-BN/B 0.89 Al 0.11 N heterojunction was the best one due to the high lattice matching. Moreover, a type-II (staggered) band alignment was formed in this heterojunction which was elucidated by X-ray photoelectron spectroscopy (XPS). The calculated valence band offset (VBO) and conduction band offset (CBO) of h-BN/B 0.89 Al 0.11 N are 1.20 and 1.14 eV, respectively. The electronic properties and formation mechanism of h-BN/ B 0.89 Al 0.11 N heterojunction were further studied by density functional theory (DFT) calculation. The existence of a built-in field (E in ) was confirmed, and the E in direction was from the BAlN side to h-BN side. The staggered band alignment was further verified in this heterojunction, and an Al−N covalent bond existed at the interface from calculated results. This work paves a pathway to construct an ultrawide band gap heterojunction for the next-generated photovoltaic application.

Hexagonal boron nitride (h-BN) is one promising material class for applications in DUV optoelectronics due to the layered structure and ultra-wide bandgap. The synthesis of h-BN with smooth surface morphology and high quality on dielectric substrates is the key to construct efficient functional devices thereon. In this study, we reported wafer-scale h-BN on c-plane sapphire substrates by metal organic chemical vapor deposition utilizing the flow modulation epitaxy (FME) with growth interruptions. The effect of the growth interruption location within FME on the surface morphology and crystalline quality of h-BN films was systematically investigated. The interruption after the TEB injection could promote the mobility of B adatoms, and the interruption after the NH3 injection could further relieve the passivation of N terminal growth fronts and mitigate the parasitic gas-phase reaction between growth precursors. By simultaneously employing interruptions after TEB and NH3 injections, the growth rate of h-BN increased significantly from 0.16 nm/min to 4.76 nm/min, and the surface roughness of 2-nm-thick h-BN was reduced to 0.587 nm. In addition, h-BN grown with an interruption solely after the NH3 injection presented the best crystallinity because the relatively slow growth rate reduced the possibility of impurity incorporation.

Zinc oxide (ZnO) is one of the most attractive materials for the preparation of ultraviolet photodetectors (UV PDs). However, the high leakage current and slow response speed significantly limit the practical applications of ZnO-based PDs. In this study, the fabrication of UV PDs based on self-assembled ZnO film has been proposed. The device has an ultra-low dark current (25 pA@10 V) and exhibits fast response speed (190 ms/68.6 ms) and high detectivity (1.91 ×10^14 Jones) for 360 nm light. The high performance can be attributed to the operating mechanism of “light-induced reduction of junction barrier height”. The analysis based on the thermionic emission theory indicates that illumination can significantly reduce both the Schottky barrier height and series resistance of the device. The prepared flexible PD based on the self-assembled film not only maintains excellent detection performance but also has strong durability and mechanical robustness. After 1000 bending-recovery cycles, the flexible device exhibits excellent repeatable on/off photo-switching behaviors. The measured time-response curves of the flexible PD under five different bending states show unaffected photocurrent, demonstrating excellent flexibility and stability.

Subwavelength freestanding InGaN/GaN quantum well microtubes with a wall thickness of about 50 nm are formed by selective release of a coherently strained bilayer heterostructure from a hosting substrate. Highly polarized spontaneous and stimulated emissions due to whispering gallery mode oscillation were observed in photoluminescence spectra at room temperature. The quality factor was increased by a factor of 3 by elevating the microtube from the substrate and reducing light leakage before threshold. A lasing threshold was characterized as low as 3 mJ/cm2. Microtubes were immersed in different liquids with refractive index variation as small as 0.01 and tested below and above threshold. The peak positions shift obviously while exhibiting excellent repeatability. Using a simple optical probe-detect method, a 5-μm diameter microtube cavity achieves a sensitivity of 40 nm/refractive index unit (RIU) and a detection limit of 6 × 10−3 RIU.