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We propose and demonstrate a cost-effective and facile electrochemical procedure to detach films with (In,Ga)N nanowires from the original Si substrate used for growth. Without ultraviolet illumination and mechanical force, this lift-off process can be completed quickly within a few seconds. The key element for the underlying mechanism is a thin AlN layer, which acts both as a buffer layer in the epitaxial process and as a sacrificial layer in the etching process. Taking advantage of the high etching selectivity of AlN over GaN, the AlN layer can be etched quickly whereas only few reactants remain on the GaN NWs, and the latter do not suffer from corrosion. Based on this lift-off procedure, a film comprising a dense ensemble of (In,Ga)N nanowires with good flexibility and transmittance can be obtained easily. We show both light emission and mechanical–electrical energy conversion for such detached films, hence substantiating perspectives for future applications. Therefore, this lift-off method for GaN-based nanowire films is promising for mass production and various devices requiring high flexibility and/or high transmittance, including wearable intelligent electronics and piezoelectric devices.

The (Al,Ga)N nanowire film with good flexibility and transparency has been achieved by a electrochemical procedure with low cost. Detaching such films can enhance the peak responsivity and decrease the decay time of ultraviolet photodetectors.

Spherical perovskite-type bismuth ferritic nanocrystals with diameters of 10-50 nm and hexagonal-shaped sillenite-type ones with sizes of 18-33 nm were synthesized at low temperatures by microwave hydrothermal process. Their structural, optical, and photocatalytic properties were investigated. The single-crystalline nature of the as-synthesized nanocrystals was confirmed by X-ray diffraction, selected area electron diffraction, and high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy investigations show that Fe element exists as the Fe 31 valence state, as well as Bi element as Bi 31 in the as-prepared bismuth ferritic nanocrystals. The visible-light photocatalytic activities evaluated by the degradation of rhodamine B in aqueous solution show that the sillenitetype bismuth ferritic nanocrystals exhibit higher photocatalytic ability than the perovskite-type ones, which can be ascribed to their small mean particle size and the unique hexagonal-shape morphology, and also the structural characteristics of sillenitetype compound. The present results demonstrate that the hexagonal-shaped sillenite-type bismuth ferritic nanocrystals can be used as novel visible-light-responsive photocatalysts for degradation of organic compounds.

The compact and low-cost surface-emitting lasers in the 3−5 μm mid-infrared (MIR) range are highly desirable for important applications such as gas detection, noninvasive medical diagnosis, and infrared scene projection. Due to the intrinsic noise of general narrow-bandgap semiconductors, the MIR is a challenging region for photonics. Here, we demonstrate the first black phosphorus (BP)-based MIR surface-emitting laser operating at room temperature fabricated with BP as the active gain materials embedded into a SiO 2 /Si 3 N 4 open microcavity on silicon. Optically pumped lasing at ∼3765 nm is successfully realized in the demonstrated device by significantly increased luminescence efficiency in the BP lamellar structure and resolving the general issues for processing BP and other two-dimensional materials as gain medium with the specific design of an open cavity. This is the first demonstration of a BP-based light-emitting device and thus paves a pathway toward monolithic integration of Si-photonics in the MIR range.

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The influence of ramp-up time of barrier growth temperature on optical properties is investigated for InGaN∕GaN quantum wells deposited on sapphire substrate by metal organic chemical vapor deposition. Three ramp-up times are used from the low and high growth temperatures for the well and barrier, respectively. The results indicate that increasing the ramp-up time leads to a blueshift of the photoluminescence (PL) peak position and a broadening of the PL emission linewidth. Similarly, “S-shaped” temperature dependences of the PL peak energy are observed in all the samples. However, very different temperature dependences of PL linewidth, such as the conventional shaped, “U-shaped,” and S-shaped, are observed in the samples with different ramp-up time. These effects are attributed to the redistribution of the In-rich clusters in the wells. Small quantum-dot-like In-rich clusters with high density are considered to be formed in the wells for the sample with a long ramp-up time, leading to the unconventional PL linewidth behavior and enhanced internal quantum efficiency.