Simple Functionalization of a Donor Monomer to Enhance Charge Transfer in Porous Polymer Networks for Photocatalytic Hydrogen Evolution.

Porous polymer networks (PPNs) are promising candidates as photocatalysts for hydrogen production. Constructing a donor-acceptor structure is known to be an effective approach for improving photocatalytic activity. However, the process of how a functional group of a monomer can ensure photoexcited charges transfer and improve the hydrogen evolution rate (HER) has not yet been studied on the molecular level.

Ultrathin Tactile Sensors with Directional Sensitivity and a High Spatial Resolution.

An ultrathin tactile sensor with directional sensitivity and capable of mapping at a high spatial resolution is proposed and demonstrated. Each sensor node consists of two gallium nitride (GaN) nanopillar light-emitting diodes. Shear stress applied on the nanopillars causes the electrons and holes to separate in the radial direction and reduces the light intensity emitted from the nanopillars.

High sensitivity bolometers based on metal nanoantenna dimers with a nanogap filled with vanadium dioxide.

One critical factor for bolometer sensitivity is efficient electromagnetic heating of thermistor materials, which plasmonic nanogap structures can provide through the electric field enhancement. In this report, using finite element method simulation, electromagnetic heating of nanorod dimer antennas with a nanogap filled with vanadium dioxide (VO) was studied for long-wavelength infrared detection. Because VO is a thermistor material, the electrical resistance between the two dimer ends depends on the dimer's temperature.

Feasibility study of nanopillar LED array for color-tunable lighting and beyond.

An LED chip containing monolithically integrated red, green, and blue channels was fabricated and characterized. Using local strain engineering in gallium nitride p-i-n nanopillar structures, each color channel emits a distinct color with emission wavelength determined entirely by the diameter of the nanopillar. The crosstalk between color channels is negligible.

Integrated parabolic nanolenses on MicroLED color pixels.

A parabolic nanolens array coupled to the emission of a nanopillar micro-light emitting diode (LED) color pixel is shown to reduce the far field divergence. For a blue wavelength LED, the total emission is 95% collimated within a 0.5 numerical aperture zone, a 3.

Flexible resistive random access memory devices by using NiO /GaN microdisk arrays fabricated on graphene films.

We report flexible resistive random access memory (ReRAM) arrays fabricated by using NiO /GaN microdisk arrays on graphene films. The ReRAM device was created from discrete GaN microdisk arrays grown on graphene films produced by chemical vapor deposition, followed by deposition of NiO thin layers and Au metal contacts. The microdisk ReRAM arrays were transferred to flexible plastic substrates by a simple lift-off technique.

Flexible GaN Light-Emitting Diodes Using GaN Microdisks Epitaxial Laterally Overgrown on Graphene Dots.

The epitaxial lateral overgrowth (ELOG) of GaN microdisks on graphene microdots and the fabrication of flexible light-emitting diodes (LEDs) using these microdisks is reported. An ELOG technique with only patterned graphene microdots is used, without any growth mask. The discrete micro-LED arrays are transferred onto Cu foil by a simple lift-off technique, which works reliably under various bending conditions.

Real-time device-scale imaging of conducting filament dynamics in resistive switching materials.

ReRAM is a compelling candidate for next-generation non-volatile memory owing to its various advantages. However, fluctuation of operation parameters are critical weakness occurring failures in 'reading' and 'writing' operations. To enhance the stability, it is important to understand the mechanism of the devices.

Microtube Light-Emitting Diode Arrays with Metal Cores.

We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (In(x)Ga(1-x)N)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al2O3) substrate. The microtube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO2) layer.

Epitaxial GaN microdisk lasers grown on graphene microdots.

Direct epitaxial growth of inorganic compound semiconductors on lattice-matched single-crystal substrates has provided an important way to fabricate light sources for various applications including lighting, displays and optical communications. Nevertheless, unconventional substrates such as silicon, amorphous glass, plastics, and metals must be used for emerging optoelectronic applications, such as high-speed photonic circuitry and flexible displays. However, high-quality film growth requires good matching of lattice constants and thermal expansion coefficients between the film and the supporting substrate.

Catalyst-free metal-organic chemical vapor deposition growth of InN nanorods.

We demonstrated the successful growth of catalyst-free InN nanorods on (0001) Al2O3 substrates using metal-organic chemical vapor deposition. Morphological evolution was significantly affected by growth temperature. At 710 degrees C, complete InN nanorods with typical diameters of 150 nm and length of approximately 3.

Microstructures of GaN thin films grown on graphene layers.

Plan-view and cross-sectional transmission electron microscopy images show the microstructural properties of GaN thin films grown on graphene layers, including dislocation types and density, crystalline orientation and grain boundaries. The roles of ZnO nanowalls and GaN intermediate layers in the heteroepitaxial growth of GaN on graphene, revealed by cross-sectional transmission electron microscopy, are also discussed.

Transferable GaN layers grown on ZnO-coated graphene layers for optoelectronic devices.

We fabricated transferable gallium nitride (GaN) thin films and light-emitting diodes (LEDs) using graphene-layered sheets. Heteroepitaxial nitride thin films were grown on graphene layers by using high-density, vertically aligned zinc oxide nanowalls as an intermediate layer. The nitride thin films on graphene layers show excellent optical characteristics at room temperature, such as stimulated emission.