Search

Graphene oxide-cysteamine-silver nanoparticle (GCA)/silver nanowire (AgNW)/GCA/colorless poly(amide-imide) (cPAI) structures based on cPAI substrates with polyimide and polyamide syntheses were fabricated to study their characteristics. A layer of electrodes was constructed using a sandwich structure—such as GCA/AgNW/GCA—with cPAI used as a substrate to increase the heat resistance and improve their mechanical properties. Furthermore, to overcome the disadvantages of AgNWs—such as their high surface roughness and weak adhesion between the substrate and electrode layers—electrodes with embedded structures were fabricated using a peel-off process. Through bending, tapping, and durability tests, it was confirmed that these multilayer electrodes exhibited better mechanical durability than conventional AgNW electrodes. Resistive random-access memory based on GCA/AgNW/GCA/cPAI electrodes was fabricated, and its applicability to nonvolatile memory was confirmed. The memory device had an ON/OFF current ratio of ~104@0.5 V, exhibiting write-once-read-many time characteristics, maintaining these memory characteristics for up to 300 sweep cycles. These findings suggest that GCA/AgNW/GCA/cPAI electrodes could be used as flexible and transparent electrodes for next-generation flexible nonvolatile memories.

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. Repeated adsorption and desorption of VOCs on zeolite filters and GC analyses allow us to evaluate the durability and reusability of the filter and could help predict the lifetime of zeolite filters in practice.

Graphene oxide (GO)–cysteamine–Ag nanoparticles (GCA)–silver nanowire (AgNW) fabricated by depositing GCA over sprayed AgNWs on PET films were proposed for transparent and flexible electrodes, and their optical, electrical, and mechanical properties were analyzed by energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, current-voltage measurements, and bending test. GCA–AgNW electrodes show optical transmittance of >80% at 550 nm and exhibit a high figure-of-merit value of up to 116.13 in the samples with sheet resistances of 20–40 Ω/◻. It was observed that the detrimental oxidation of bare AgNWs over time was considerably decreased, and the mechanical robustness was improved. To apply the layer as an actual electrode in working devices, a Pt/GO/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/GCA–AgNW/polyethylene terephthalate structure was fabricated, and resistive switching memory was demonstrated. On the basis of these results, we confirm that the proposed GCA–AgNW layer can be used as transparent and flexible electrode.

We present the first demonstration of the environmental application of a polyimide film (Kapton) with patterned thru-holes as a novel, efficient, flexible, recyclable, and active particulate matter (PM) air filter. The Kapton air filter captures PM using micro-sized thru-holes and the strong electrostatic force because of its high work function. It is highly efficient, transparent, flexible, and heat-resistant. Furthermore, it can be recycled simply by washing it with tap water. The proposed PM filter is a promising candidate for use as a highly efficient and economical recyclable air filter for home appliances, such as air-purifiers, air-conditioners, and humidifiers, as well as industrial filtration systems.

The interfacial electronic structures of a bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) grown on vanadium pentoxide (V2O5) thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO) level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO) level of the C60 layer was determined and compared with that grown on an indium tin oxide (ITO) substrate. The energy difference of a heterojunction on all V2O5 was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V2O5 than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C60/ZnPc on V2O5 and ITO.

The intracavity frequency doubling of a diode-pumped vertical-external-cavity surface-emitting lasers (VECSEL) has produced highly efficient blue lasers. The number of quantum wells (QWs) is increased and [Al.sub.0.3][Ga.sub.0.7]As carrier blocking layers are inserted in order to enhance recombination efficiency of the QW and the diamond heat spreader is directly bonded to VECSEL chip by using a capillary action for distilled water in order to solve the thermal problem.

The experimental determination of temperature dependence of piezoelectric constant is reported. This leads to the strain-induced component of the pyroelectric coefficient.

Energy level alignment between pentacene molecules on Au and noninteracting substrate SnS2 was investigated. Molecular rows showed distinct separation distances and molecular orientations.

Demagnetization of a ferrimagnetic material by a shock wave was detected. This effect could be harnessed by developing the explosive driven power sources.

This paper reports a promising method to decrease the operating temperature during electrolysis of natural ilmenite to produce a porous and laminar flake-type intermetallic ferrotitanium (FexTi, x = 1, 2) with a thickness of less than 1 µm by choosing a LiCl-Li2O electrolyte with a lower operating temperature (625 °C) under an inert atmosphere. Results indicate that the Li2O content in the electrolyte has a key effect on the phase transformation of natural ilmenite occurring in the electrochemical reduction process. Full conversion of natural ilmenite into ferrotitanium products can be achieved when the Li2O amount in the electrolyte and the cell voltage are approximately 1 wt.% and -2.5 V, respectively. In addition, the electrochemical reduction mechanism of natural ilmenite is proposed and discussed based on our experimental results and thermodynamic analysis. [ABSTRACT FROM AUTHOR]

The temperature dependence of excitonic properties for an InGaAs/GaAs p-i-n multiquantum well structure grown on a (111)B GaAs substrate by molecular-beam epitaxy is studied by using photoreflectance spectroscopy, in which the pyroelectric effect is considered. The optical-phonon energy and strength of electron-phonon coupling for the crystallographic directions of the material system, as well as the interface roughness from an analysis of the temperature dependence of PR broadening parameters are determined.

The effect of the properties of an intracavity diamond heat spreader on the lasing performance of vertical-external cavity surface-emitting lasers was investigated. It was found that the rise in temperature while using natural diamond heat-spreader sample was 15 [plusmn] 2 degrees Celsius higher.

An investigation on the heterinterfaces of a strained piezoelectric InGaAs/GaAs single quantum well structure grown on a (111) A GaAs substrate by metalorganic vapor phase epitaxy by employing photoreflectance spectroscopy over the temperature range 11-300 K. The results in conjunction with the observation of a narrow photoluminescence linewidth of 9.1 meV indicate the achievement of essentially atomically smooth interfaces in a highly strained (~1%) piezoelectric InGaAs/GaAs wuantum well structure.

We report an improved optical pumping efficiency in a vertical-external-cavity surface-emitting laser (VECSEL) by employing the double-band mirror (DBM), which acts as a pump beam reflector as well as a cavity mirror. The optical pumping efficiency of a VECSEL with the DBM was increased by 23%, as compared to one with the conventional distributed Bragg reflector. It was found that the use of the DBM was more effective in the VECSEL with the shorter absorption layer thickness. [ABSTRACT FROM PUBLISHER]

We report a high-power fundamental transverse mode operation of an optically pumped 920-nm vertical-external- cavity surface-emitting laser. The effects of the gain related structural parameters on the laser performance are investigated. Based on the optimization of the gain structure and the thermal management, a maximum pump-limited output power of 12 W in a TEM00 mode with a slope efficiency of 58% (input power of 24 W) was achieved at room temperature. [ABSTRACT FROM PUBLISHER]

We propose a novel lens-less optical end-pumping scheme and report on the development of a highly efficient and compact green vertical-external-cavity surface-emitting laser (VECSEL). A constant-wave pump-power-limited maximum green output power of 1.1 W and an optical-to-optical conversion efficiency of as high as ~15.7% (=1.1 W/7 W) were achieved using a single chip pump laser diode placed directly behind the VECSEL structure without any beam focusing and shaping optical elements. [ABSTRACT FROM PUBLISHER]

We investigate the effect of relative wavelength difference between material gain and resonance peaks on lasing performance in vertical-external-cavity surface-emitting lasers (VECSELs). We propose a measurement method of the wavelength-dependent modal gain profiles by inserting a birefringent filter inside a cavity in order to modulate the optical loss according to the wavelength. With knowledge of the detailed gain profiles, we achieve a stable green output power of 3.3 W and a power conversion efficiency (= green output power/pump input power) of 17% in VECSEL with a LiB3O5 crystal as an intracavity frequency doubler [ABSTRACT FROM PUBLISHER]

The authors report on the development and demonstration of the high power operation of optically end-pumped vertical external cavity surface emitting laser devices emitting at 532 and 460 nm. 2.7 W green and 1.4 W blue output powers were achieved with a good beam quality by intracavity frequency doubling with second harmonic generation crystal. High efficiency and good beam quality are attributed to the enhanced thermal management by the diamond heat spreader directly bonded to the gain region and effective optical pumping by placing the pump laser diode behind the laser structure. [ABSTRACT FROM AUTHOR]

We present 660-nm GaInP-AlGaInP ridge multiple-quantum-well laser diodes (LDs) reliably operating at high output power over 200 mW at 70°C not showing unstable higher order lateral modes owing to an adoption of a dry etching method instead of a conventional chemical wet etching for realizing steep ridge sidewalls. Employing an optimized two-step n-cladding layer LDs produced very narrow horizontal and vertical beam divergence angles of 8.6° and 15.3°, respectively. To the best of our knowledge, this vertical beam divergence angle is the lowest value ever reported in high-power 660-nm LDs operating over 200 mW and is expected to play an important role in minimizing the coupling loss between LD and passive optical components in digital versatile disc system. [ABSTRACT FROM PUBLISHER]

We propose a new layer design for 660-nm GaInP-AlGaInP quantum-well laser diodes employing a two-step n-cladding layer and demonstrate the feasibility of achieving a reduced vertical beam divergence angle of as low as 14.8° with a relatively small decrease in the optical confinement factor by theoretical simulations and experimental observations. [ABSTRACT FROM PUBLISHER]