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Thermoresponsive behavior of stereoisomers of a dense triazole polymer was studied; mixtures of the isotactic one underwent thermoresponsive gel-to-sol transition, and aqueous solutions of the syndiotactic one underwent LCST-type phase transition.

Thermoresponsive water-soluble polymers, aqueous solutions of which undergo lower critical solution temperature (LCST)-type phase separation, have been investigated in detail for several decades. To develop LCST-type thermoresponsive polymers with new polymer backbone, 4-azido-5-hexynamide (AHA) derivatives were designed as monomers for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization. AHA derivatives carrying secondary amide side chains, that is, 4-azido-N-methyl-5-hexynamide (M), 4-azido-N-ethyl-5-hexynamide (E), and 4-azido-N-isopropyl-5-hexynamide (iP), were first synthesized and polymerized by CuAAC to obtain polymers (poly(M), poly(E), and poly(iP)). Contrary to our expectation, poly(M), poly(E), and poly(iP) were insoluble in water and many organic solvents presumably because of the formation of hydrogen bonding between the amide side chains or between the amide side chains and triazole residues in the backbone. Thus, AHA derivatives carrying tertiary amide side chains, that is, 4-azido-N,N-dimethyl-5-hexynamide (MM), 4-azido-N-ethyl-N-methyl-5-hexynamide (ME), 4-azido-N-isopropyl-N-methyl-5-hexynamide (MiP), and 4-azido-N,N-diethyl-5-hexynamide (EE), were also synthesized and polymerized to yield polymers (poly(MM), poly(ME), poly(MiP), and poly(EE)). These polymers were soluble in a number of common organic solvents. It is noteworthy that poly(MM) and poly(ME) were also soluble in water. The phase separation behavior of 1.0 wt % aqueous solutions of poly(MM) and poly(ME) was then investigated by transmittance measurements. These data indicated that poly(ME) was an LCST-type thermoresponsive polymer, whereas poly(MM) was not. A large hysteresis was observed in the transmittance measurements for the poly(ME) aqueous solution because of slow rehydration after phase separation. The phase separation behavior was investigated preliminarily by differential scanning calorimetry and 1H NMR.

The morphology and crystalline quality of p-GaN shells on coaxial GaInN/GaN multiple quantum shell (MQS) nanowires (NWs) were investigated using metal-organic chemical vapor deposition. By varying the trimethylgallium (TMG) flow rate, Mg doping, and growth temperature, it was verified that the TMG supply and growth temperature were the dominant parameters in the control of the p-GaN shape on NWs. Specifically, a sufficiently high TMG supply enabled the formation of a pyramid-shaped NW structure with a uniform p-GaN shell. The ratio of the growth rate between the c- and m-planes on the NWs was calculated to be approximately 0.4545. High-angle annular dark-field scanning transmission electron microscopy characterization confirmed that no clear extended defects were present in the n-GaN core and MQS/p-GaN shells on the sidewall. Regarding the p-GaN shell above the c-plane MQS region, only a few screw dislocations and Frank-type partial dislocations appeared at the interface between the serpentine c-plane MQS and the p-GaN shell near the tips. This suggested that the crystalline quality of the MQS structure can trigger the formation of screw dislocations and Frank-type partial dislocations during the p-GaN growth. The growth mechanism of the p-GaN shell on NWs was also discussed. To inspect the electronic properties, a prototype of a micro light-emitting diode (LED) with a chip size of 50 × 50 μm2 was demonstrated in the NWs with optimal growth. By correlating the light output curve with the electroluminescence spectra, three different emission peaks (450, 470, and 510 nm) were assignable to the emission from the m-, r-, and c-planes, respectively.

Fragmented cytokeratin 18 (fCK18) released from epithelial cells undergoing apoptosis is widely studied in various diseases. However, fCK18 measurement is not utilized in clinical practice due to imprecise disease-state cutoff values. Therefore, we set out to generate new monoclonal antibodies (mAbs) and a recombinant fCK18 (rfCK18) calibrator in an effort to develop a highly sensitive chemiluminescent enzyme immunoassay (CLEIA). New capture mAb (K18-624) had a high binding ability compared to the current commercial antibody. New detection mAb (K18-328) recognized 323S-340G of CK18. A rfCK18 was expressed in the soluble fraction of E. coli when the N-terminal region (260 amino acid residues) of CK18 was truncated. Analysis of performance and measurement of human fCK18 were evaluated using K18-624 and K18-328 in a highly sensitive CLEIA. The coefficients of variation (CV) for within-run and between-day repeatability were below 10% and the recoveries were in the range of 15%. The detection sensitivity was 0.056 ng/mL. Serum fCK18 levels were significantly increased in non-alcoholic steatohepatitis (NASH) patients when compared to healthy individuals. Our new fCK18 mAbs showed high affinity and sensitivity. CLEIA using our new antibodies will be useful in measuring fCK18 in human blood thereby generating accurate clinical diagnoses of human liver diseases.

Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.

Here, we systematically investigated the growth conditions of an n-GaN cap layer for nanowire-based light emitters with a tunnel junction. Selective-area growth of multiple quantum shell (MQS)/nanowire core-shell structures on a patterned n-GaN/sapphire substrate was performed by metal-organic vapor phase epitaxy, followed by the growth of a p-GaN, an n++/ p++-GaN tunnel junction, and an n-GaN cap layer. Specifically, two-step growth of the n-GaN cap layer was carried out under various growth conditions to determine the optimal conditions for a flat n-GaN cap layer. Scanning transmission electron microscopy characterization revealed that n++-GaN can be uniformly grown on the m-plane sidewall of MQS nanowires. A clear tunnel junction, involving 10-nm-thick p++-GaN and 3-nm-thick n++-GaN, was confirmed on the nonpolar m-planes of the nanowires. The Mg doping concentration and distribution profile of the p++-GaN shell were inspected using three-dimensional atom probe tomography. Afterward, the reconstructed isoconcentration mapping was applied to identify Mg-rich clusters. The density and average size of the Mg clusters were estimated to be approximately 4.3 × 1017 cm-3 and 5 nm, respectively. Excluding the Mg atoms contained in the clusters, the remaining Mg doping concentration in the p++-GaN region was calculated to be 1.1 × 1020 cm-3. Despite the lack of effective activation, a reasonably low operating voltage and distinct light emissions were preliminarily observed in MQS nanowire-based LEDs under the optimal n-GaN cap growth conditions. In the fabricated MQS-nanowire devices, carriers were injected into both the r-plane and m-plane of the nanowires without a clear quantum confinement Stark effect.

GaInN/GaN multiple quantum shells (MQS) nanowires and p-GaN shells were embedded with n-GaN layers through tunnel junction (TJ) shells using metalorganic chemical vapor deposition (MOCVD) method. The MQS nanowires were selectively grown on n-GaN/sapphire or GaN substrates. The fabrication process of laser structures with different resonators of 600500, 750, 1000 μm, and cavity widths of 7, 12, and 17 μm were investigated with insulating layer on the sidewalls of the ridge. The structures of the fabricated devices were characterized by scanning electron microscope (SEM) and current-voltage-light output characteristics were evaluated. Two different methods for mirror formation, etching and cleavage, were developed for the laser devices. During the investigation, a superior mirror formation suffered from the difference in etching rate between GaInN and GaN, generating concaves in the MQS region. Bluegreen light emission was observed from the entire ridge surface of the MQS index-guided laser structures. A maximum current density of emission at 17.9 kA/cm2 has been confirmed in the devices. The electroluminescence and cathodoluminescence measurements demonstrated that the r-plane and c-plane at the top of the MQS are dominant at low current densities, and the m-plane emission becomes stronger as the current density increases.

A tunnel junction and a n-GaN cap layer grown on the multi-quantum shells (MQS) /nanowires are introduced to decrease the resistivity and optical loss. The selective-area growth of the MQS/nanowire core-shell structures on the template was performed by metalorganic vapour phase epitaxy (MOVPE). Further, the MQS structure was covered with the tunnel junction and the n-GaN cap layer. Here, the growth conditions of the n-GaN cap layer were systemically investigated. The effect of p-GaN shape on the morphology of grown n-GaN cap layer was also assessed.

In this study, the growth mechanisms of n-type gallium nitride (GaN) cap layers for embedding nanowire-based multi-quantum-shell (NW-MQS) with a tunnel junction were investigated using the metal–organic vapor-phase epitaxy method. Herein, instead of a p-type GaN layer, n-type GaN cap layers were applied as a contact layer to the anode electrode via a tunnel junction. NW-MQSs were prepared in a rectangular grid arrangement aligning with the m- and a-axis of GaN. The growth mode of the cap layers was controlled in three stages using different growth pressures and temperatures. The first cap layer was a faceted growth mode primarily comprising the r-plane, the second was a lateral growth mode that expanded the area of the c-plane, and the third was an acceleration of lateral growth. Finally, cap layers with a flat surface were realized. Void formation in the cap layers occurred only between the NW-MQSs along the m-axis of GaN. This observation can be attributed to the difference in the coalescence of the cap layers in the a- and m-axis directions. We believe that the NW-MQS structure with the cap layer that was optimized in this study can be used as a highly efficient optical device.

This study aimed to investigate and analyze the impurity doping characteristics in tunnel junctions (TJs) grown on core–shell structures, comprising GaInN/GaN multiple-quantum-shells (MQSs) and GaN nanowires. To this end, the impurity, structural, and electrical properties of the samples were characterized by scanning electron microscopy, scanning transmission electron microscopy, atom probe tomography (APT), nanoscale secondary ion mass spectrometry (NanoSIMS), and electroluminescence of the device which was fabricated for a prototype laser device to demonstrate an electrical operation of the MQSs layer. From the experimental results of NanoSIMS and APT, we demonstrated that the Mg-related problems in the TJ, such as the diffusion to the n++-GaN layer from the p+-GaN layer and formation of clusters in p+-GaN, are critical. Consequently, they cause a high operating voltage and dot-like spot emission of the light-emitting device. Based on the analysis, we suggested remedies and strategies to further improve the TJs that work well.

In this study, we discuss the influence of SiH4 flow rates on the structural and optical properties of GaN nanowires (NWs) with multiple-quantum-shells (MQSs). To this end, we prepared two n-GaN core NW samples with different SiH4 flow rates. Subsequently, MQS active layers of the same structure were grown on each n-GaN core NW under identical growth conditions. The samples were characterized by scanning electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray, and cathodoluminescence (CL) mapping. From the experimental results, we ascertained that a Si-rich layer was created between the sidewall of the NWs and MQSs, in which the number of Si atoms was mainly determined by the SiH4 flow rate. These Si atoms diffused into the MQSs during the growth, and significantly impacted the structural and optical properties, such as the shape and crystalline quality of the MQSs and NWs, and the CL intensity of the MQSs. On the basis of experimental results, we conclude that the SiH4 flow rate during the NW growth plays a critical role in the performance of an MQS-based optoelectronic semiconductor device.

To achieve both the reduction of threading dislocation density (TDD) and the enhancement of light extraction efficiency (LEE) of light-emitting diodes (LEDs), a two-directional stripe-patterned sapphire substrate (TPSS) was fabricated. First, a stripe pattern parallel to the a-axis of Al2O3 was formed on an as-received c -sapphire wafer and then a second stripe pattern rotated around 3° from the m-axis of Al2O3 was formed on the first stripe PSS. The light output power of TPSS LEDs was around 1.25 times higher than that of LEDs on a flat sapphire substrate. This enhancement is caused by the increase of both the internal quantum efficiency (IQE) and the LEE. On the other hand, although the LED on TPSS with the second stripe just parallel to the m-axis of Al2O3 showed a similar enhancement ratio of the light output power, the current leakage of this LED increased with the concentration of threading dislocations on the surface of LEDs. Stripes rotated 3° from the m-axis of Al2O3 changed the growth mode and realized GaN films with a smooth surface without pit formation. Therefore, the misalignment of the stripe from the m-axis of Al2O3 will become a new design parameter for realizing high-efficiency reliable LEDs. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low-temperature-deposited (LT-) AlN layers and the initial growth of GaN on a- and c-sapphire have been investigated and compared. The as-deposited LT-AlN layers on both a- and c-sapphire are composed of high-density islands. By annealing, the islands become large. The density of islands on a- and c-sapphire are 5.6 × 1010 and 7.9 × 1010 cm-2, respectively, indicating that the evolution of the solid phase epitaxy of AlN islands induced by annealing is different on a- and c-sapphire. The moire spacings obtained by plan-view electron microscopy reveal that the strain of the AlN islands on a-sapphire is larger than that of islands on c-sapphire. These results imply that development of the solid phase epitaxy is influenced by the strain. The coalescence of GaN islands grown on a-sapphire, which has larger AlN islands, is advanced compared with that of islands on c-sapphire. The relationship between the annealed AlN island density and the threading dislocation (TD) density in the GaN films is investigated on a- and c-sapphire. The TD density of the GaN films is small when the density of annealed AlN islands is low. These results indicate that decreasing the island density of the annealed AlN layers is essential for improving the crystalline quality of GaN films. It is therefore important to control the solid phase epitaxy of LT-AlN layers by annealing. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A sapphire substrate with a grooved stripe pattern along different radial directions was prepared to investigate the effects of stripe direction on the growth mode and threading dislocation (TD) behavior of GaN films. When the stripe direction is oriented parallel to [101̄0]sapphire, the GaN films have a triangular structure that is formed by the GaN{101̄1} facets. As the stripe direction rotates from [101̄0]sapphire, nanosteps with a step height of around 80 nm are formed on the GaN{101̄1} facets and then the coalescence of GaN on the ridges and grooves advances. GaN films with a smooth surface and a TD density as low as 2.0×108 cm-2 were achieved when the stripe direction was rotated 3° from [101̄0]sapphire. Our result indicates that the surface roughness and TD density of GaN films can be controlled by precisely adjusting the angle of the stripe direction from [101̄0]sapphire.

Services for autistic adults are still not institutionally organized in Japan. Because of the urgent problems of these adults, they are now receiving training under the category of services for the mentally retarded, and there are more than 10 facilities of this type around the country. These facilities can be divided into three types according to the process of their establishment: (1) facilities promoted and organized by a group of parents; (2) facilities operated by an existing social welfare organization for the benefit of community residents; and (3) facilities established by administrative agencies or an existing social welfare organization in response to lobbying by parents and volunteers. Each facilities has its own character and its own problems according to the process of its establishment and the nature of the surrounding community. Asake Gakuen is the first specialized home for autistic adults in Japan. It was designed to be a model for facilities for the developmentally disabled that focus on autistic adults. It facilitates social independence through on-site work experience and ties with the local community. The details of the establishment of Asake Gakuen and its present condition are introduced, and its present conditions, policies and problems concerning the role of facilities for autistic adults in Japan are discussed.

The fabrication of a blue m-plane GaInN light emitting diode (LED) grown on an m-plane GaN layer grown on a 3-in. patterned sapphire substrate is reported. The output power of the LED was approximately 3 mW at the wavelength of 461 nm, a driving current of 20 mA, and a forward voltage of 3.5 V. This is the first report of nonpolar or semipolar blue LEDs grown on hetero-substrates with milliwatt scale output power.

Nonpolar m-plane GaN films have been grown by metalorganic vapor-phase epitaxy on patterned a-plane sapphire substrates (diameter: 3 in.) without dielectric masks made of materials such as SiO2. The m-plane GaN layer had a smooth and transparent surface over the entire area of the substrate. Furthermore, the epitaxial relationships between the m-plane GaN film and the patterned a-plane sapphire substrate were as follows: [0001]GaN∥[0001]Sapphire and [1120]GaN∥[1010]Sapphire. The full width at half maximum values of the X-ray rocking curves for (1010) GaN along [1120]GaN and [0001]GaN were found to be 396 and 565 arcsec, respectively.

Summary In grinding operation, the sharpenss of the wheel face is extremely important because it determines the grinding forces, heat generation, size accuracy, surface integrity, etc. Nevertheless, there has been no adequate method for its evaluation. The method presented here is a rational and simple one in which a steel ball is ground by the wheel face to be tested under a constant load, and the metal removal rate is indicated as the function of widely varied normal pressure. It is shown that this method can sensitively evaluate the sharpness which is varied by the orientation of diamond dresser, the dressing feed and the amount of metal removed by the wheel face. Furthermore, the best surface finish attainable by the wheel face is shown on the steel ball.