Convergence Gas Sensors with One-Dimensional Nanotubes and Pt Nanoparticles Based on Ultraviolet Photonic Energy for Room-Temperature NO Gas Sensing.

Zinc oxide (ZnO) is a promising material for nitrogen dioxide (NO) gas sensors because of its nontoxicity, low cost, and small size. We fabricated one-dimensional (1D) and zero-dimensional (0D) convergence gas sensors activated via ultraviolet (UV) photonic energy to sense NO gas at room temperature. One-dimensional ZnO nanorod (ZNR)-based and ZnO nanotube (ZNT)-based gas sensors were synthesized using a simple hydrothermal method.

Self-array of one-dimensional GaN nanorods using the electric field on dielectrophoresis for the photonic emitters of display pixel.

Recently, high-efficiency III-nitride photonic emitters (PEs) for next-generation displays have been studied. Although micro-light-emitting diodes (μ-LEDs), one of the III-nitride PEs, have attracted considerable attention because of their high efficiency and size flexibility, they have encountered technical limitations such as high defect rate, high processing cost, and low yield. To overcome these drawbacks of μ-LEDs, a lot of research on PEs using one-dimensional (1D) gallium nitride-related nanorods (GNRs) capable of horizontally self-positioning on the electrodes has been carried out.

Ultraviolet light-emitting diode-assisted highly sensitive room temperature NO gas sensors based on low-temperature solution-processed ZnO/TiO nanorods decorated with plasmonic Au nanoparticles.

Nanostructured semiconducting metal oxides such as SnO, ZnO, TiO, and CuO have been widely used to fabricate high performance gas sensors. To improve the sensitivity and stability of gas sensors, we developed NO gas sensors composed of ZnO/TiO core-shell nanorods (NRs) decorated with Au nanoparticles (NPs) synthesized via a simple low-temperature aqueous solution process, operated under ultraviolet irradiation to realize room temperature operation. The fabricated gas sensor with a 10 nm-thick TiO shell layer shows 9 times higher gas sensitivity and faster response and recovery times than ZnO NR-based gas sensors.

Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH Growth Interruption.

We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time.

TiO Nanorods and Pt Nanoparticles under a UV-LED for an NO Gas Sensor at Room Temperature.

Because the oxides of nitrogen (NO) cause detrimental effects on not only the environment but humans, developing a high-performance NO gas sensor is a crucial issue for real-time monitoring. To this end, metal oxide semiconductors have been employed for sensor materials. Because in general, semiconductor-type gas sensors require a high working temperature, photoactivation has emerged as an alternative method for realizing the sensor working at room temperature.

Ni-Cu Nanoparticles-Embedded Ag-Based Reflector for High-Efficiency Light-Emitting Diodes.

We investigated the use of a silver reflector embedded with Ni-Cu nanoparticles to achieve low resistance and high reflectivity in GaN-based flip-chip light-emitting diodes. Compared to a single layer of Ag, the NC-NPs/Ag reflector exhibits a higher light reflectance of ~90% at a wavelength of 450 nm, a lower contact resistance of 4.75 × 10 II cm², and improved thermal stability after annealing at 400°C.

Self-Aligned Hierarchical ZnO Nanorod/NiO Nanosheet Arrays for High Photon Extraction Efficiency of GaN-Based Photonic Emitter.

Advancements in nanotechnology have facilitated the increased use of ZnO nanostructures. In particular, hierarchical and core-shell nanostructures, providing a graded refractive index change, have recently been applied to enhance the photon extraction efficiency of photonic emitters. In this study, we demonstrate self-aligned hierarchical ZnO nanorod (ZNR)/NiO nanosheet arrays on a conventional photonic emitter (C-emitter) with a wavelength of 430 nm.

Ultraviolet Photoactivated Room Temperature NO Gas Sensor of ZnO Hemitubes and Nanotubes Covered with TiO Nanoparticles.

Prolonged exposure to NO can cause lung tissue inflammation, bronchiolitis fibrosa obliterans, and silo filler's disease. In recent years, nanostructured semiconducting metal oxides have been widely used to fabricate gas sensors because of their unique structure and surface-to-volume ratio compared to layered materials. In particular, the different morphologies of ZnO-based nanostructures significantly affect the detection property of NO gas sensors.

Quantitative analysis of adsorption and desorption of volatile organic compounds on reusable zeolite filters using gas chromatography.

In this study, we propose a method to quantitatively analyze the concentration of VOCs adsorbed on zeolite filters via gas chromatography (GC). The sampled VOCs from the filters with ethanol as a solution were characterized using GC to determine the concentration of the adsorbed VOCs by comparing the areas of GC peaks of the detected VOCs and ethanol. The proposed method also enabled determination of the desorption (regeneration) conditions of the zeolite filters according to heating temperature and time for various VOCs.

Polarized ultraviolet emitters with Al wire-grid polarizers fabricated by solvent-assisted nanotransfer process.

Polarized ultraviolet (UV) emitters are essential for various applications, such as photoalignment devices for liquid crystals, high-resolution imaging devices, highly sensitive sensors, and steppers. To increase the high polarization ratio (PR) of a UV emitter, the grating period should be decreased than that of the visible emitter. However, the fabrication of the short period grating directly on UV emitters is still limited.

Transparent Conductive Electrodes of -Ga₂O₃/Ag/-Ga₂O₃ Multilayer for Ultraviolet Emitters.

We investigated the optical and electrical properties of a -Ga₂O₃/Ag/-Ga₂O₃ multilayer transparent conductive electrode deposited on an -Al2O₃ (0001) substrate. For the deposition of a continuous Ag layer, we preliminarily performed anultraviolet-ozone pretreatment of the Ga₂O₃ bottom layer. To obtain a stable -phase of Ga₂O₃, the -Ga₂O₃/Ag/-Ga₂O₃ multilayer was annealed at 700 °C under N₂ atmosphere.

High Efficiency Flip Chip-Based UV Emitter with Indium Tin Oxide Nano Grains/Al Reflector and Periodic Microhole Arrays.

We propose a high efficiency flip chip-based ultraviolet (UV) emitter with aluminum (Al) reflector that includes indium tin oxide (ITO) nano grains for current injection between the Al and -AlGaN layer. Al has attracted attention as a reflector for high efficiency UV emitters because of its high reflectance in the UV region. To improve the efficiency of UV emitter, we generated periodic microhole arrays on the -AlGaN layer, which serve as a scattering center in the flip chip structure and enhance the light extraction efficiency.

Preparation of Polyimide/Graphene Oxide Nanocomposite and Its Application to Nonvolatile Resistive Memory Device.

2,6-Diaminoanthracene (AnDA)-functionalized graphene oxide (GO) (AnDA-GO) was prepared and used to synthesize a graphene oxide-based polyimide (PI-GO) by the in-situ polymerization method. A PI-GO nanocomposite thin film was prepared and characterized by infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and UV-visible spectroscopy. The PI-GO film was used as a memory layer in the fabrication of a resistive random access memory (RRAM) device with aluminum (Al) top and indium tin oxide (ITO) bottom electrodes.

Wide Bandgap Transparent Conducting Electrode of FTO/Ag/FTO Structure for Ultraviolet Light-Emitting Diodes.

We investigated the effect of the Ag interlayer thickness on the structural, electrical and optical properties of FTO/Ag/FTO structures designed for use in wide bandgap transparent conducting electrodes. The top and bottom FTO layers were deposited on α-Al2O3 (0001) substrates via RF magnetron sputtering at 300 °C and Ag interlayers were deposited using an e-beam evaporator system. We optimized the figure of merit by changing the thickness of the inserted Ag interlayer from 10 nm to 14 nm, achieving a maximum value of 2.

High Reliability of Ag Reflectors with AgCu Alloy for High Efficiency GaN-Based Light Emitting Diodes.

We propose an Ag reflector layer with an AgCu alloy layer as a thermally reliable reflector for high power flip-chip and vertical light emitting diodes (LEDs). By annealing the deposited Ag and Cu layers, intermixed grains and grain boundaries from the alloyed AgCu layer were formed on the LEDs, and CuO nano dots precipitated at the grain boundaries. A thick AgCu layer was deposited to cover the AgCu alloy layer.

Self-standing ZnO nanotube/SiO core-shell arrays for high photon extraction efficiency in III-nitride emitter.

Self-standing ZnO nanotube (ZNT) arrays were fabricated on the surface of a GaN-based emitter with an indium tin oxide (ITO) transparent layer using a hydrothermal method and temperature cooling down process. For the greater enhancement of photon extraction efficiency, ZNT/SiO core-shell nanostructure arrays were fabricated on the emitter with a 430 nm wavelength. The optical output power of ZNT/SiO core-shell arrays on the emitter with ITO electrode was remarkably enhanced by 18.

Ultraintense UV emission from ZnO-sheathed ZnS nanorods.

Short-wavelength luminescence is essential for high-performance optoelectronic device applications. There have been efforts to obtain intense ultraviolet (UV) emission by encapsulating ZnO one-dimensional (1D) nanostructures with materials such as ZnS. However, the encapsulation of ZnS 1D nanostructures with ZnO has not been reported.

Self-assembled indium tin oxide nanoball-embedded omnidirectional reflectors for high photon extraction efficiency in III-nitride ultraviolet emitters.

The control of the refractive index and electrical conductivity in the dielectric layer of omnidirectional reflectors (ODRs) is essential to improve the low efficiency of AlGaN-based UV emitters. Here, we report self-assembled indium tin oxide (ITO) nanoball-embedded omnidirectional reflectors (NODRs) for use in high-efficiency AlGaN-based UV emitters at 365 nm. These NODRs consisted of a reflective Al layer, a self-assembled conducting ITO nanoball layer for current injection and spreading, and nanovoids that provided a low refractive index to achieve highly efficient UV emitters.

Carrier Transport at Metal/Amorphous Hafnium-Indium-Zinc Oxide Interfaces.

In this paper, the carrier transport mechanism at the metal/amorphous hafnium-indium-zinc oxide (a-HIZO) interface was investigated. The contact properties were found to be predominantly affected by the degree of interfacial reaction between the metals and a-HIZO; that is, a higher tendency to form metal oxide phases leads to excellent Ohmic contact via tunneling, which is associated with the generated donor-like oxygen vacancies. In this case, the Schottky-Mott theory is not applicable.

Fabrication and NO2 gas sensing performance of TeO2-core/CuO-shell heterostructure nanorod sensors.

Unlabelled: TeO2-nanostructured sensors are seldom reported compared to other metal oxide semiconductor materials such as ZnO, In2O3, TiO2, Ga2O3, etc. TeO2/CuO core-shell nanorods were fabricated by thermal evaporation of Te powder followed by sputter deposition of CuO. Scanning electron microscopy and X-ray diffraction showed that each nanorod consisted of a single crystal TeO2 core and a polycrystalline CuO shell with a thickness of approximately 7 nm.

Room temperature, ppb-level NO2 gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination.

Reports of the gas sensing properties of ZnSe are few, presumably because of the decomposition and oxidation of ZnSe at high temperatures. In this study, ZnSe nanowires were synthesized by the thermal evaporation of ZnSe powders and the sensing performance of multiple-networked ZnSe nanowire sensors toward NO2 gas was examined. The results showed that ZnSe might be a promising gas sensor material if it is used at room temperature.

Enhancement of light extraction efficiency of GaN-based light-emitting diodes by ZnO nanorods with different sizes.

The improvement of the optical output power of GaN-based light emitting diodes (LEDs) was achieved by employing nano-sized flat-top hexagonal ZnO rods. ZnO nanorods (NRs) with the average diameters of 250, 350, and 580 nm were grown on p-GaN top surfaces by a simple wet-chemical method at relatively low temperature (90 degrees C) to investigate the effect of the diameter of ZnO NRs on the light extraction efficiency. Consequently, the enhancement by the factor of as high as 2.

High efficiency GaN-based light emitting diode with nano-patterned ZnO surface fabricated by wet process.

The improvement of the optical output power of GaN-based light emitting diodes (LEDs) was achieved by a novel bi-layer transparent top electrode scheme. The proposed bi-layer structure is composed of a Ga-doped ZnO layer with nano-patterns obtained solely by wet etching process and an Indium Tin Oxide p-type transparent conducting electrode layer. We employed various wet-etching conditions to maximize light extraction efficiency and it was observed that the crystal morphologies of nano-patterns and optoelectronic properties are dependent on etching duration.