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Thyroid stimulating hormone (TSH) plays a critical role in regulating physiological symptoms in human, thus, it is important to detect TSH with high sensitivity and specificity is urgently needed in the human serum sample. In this paper, we proposed a strategy to detect TSH antigen using a membrane-based microwave-mediated analytical device developed for highly responsive electrochemical immunoassay with sandwich enzyme-linked immunosorbent assay (ELISA) format. Experimental assay was done with different TSH antigen concentrations. It was found that the immunoassay was able to detect TSH antigen as low as 0.2 mIU/L. The total detection time from preparation of samples to measurement was within 60 min. The specificity of this immunoassay was proven that against unspecific proteins as the almost low signal was obtained for all tested solutions. Finally, exploratory experiments using standard human serum samples with TSH antigens were carried out prior to a successful trial using clinical human serum samples. Our results indicate that this membrane-based microwave-mediated analytical electrochemical immunoassay device could be used as a new platform for low cost, sensitive, specific, swift, and point-of-care diagnosis of TSH. Moreover, the advance system could define a powerful point-of-care tool in the next generation of technology for detecting and signaling biomarkers at early stages by using electrochemical immunosensor.

A repeated usable electrode sensor for the measurement of glucose in urine has been developed. For improvement of the selectivity in measuring glucose in urine, we fabricated the Pt electrode coated with multilayered composite of glucose oxidase (GOX) and ascorbate oxidase (AOX). This simple layer structure could deliver more electrons from glucose oxidation without interference from ascorbic acids by first oxidizing the ascorbic acids present in urine. Results showed that our newly developed Pt electrode is capable of quantifying the concentrations of glucose in urine in the range between 0 and 1000 mg/dL, as well as maintaining its detection stability during 200 times of repeated measurements. This repeatable use of the sensor is attributable to the solidified structure of AOX and GOX layer.

The increase in worldwide trade has caused the quality maintenance of commercialized agriproducts to be crucial in keeping its economic value. In recent years, methyl bromide (MB) has been used dominantly during quarantine and pre-shipment, despite it being an environmental hazard with global repercussions. Through this study, it was shown that Arabidopsis thaliana’s 2 h exposure to the MB treatment displayed no signs of phytotoxicity, whereas its 4 h exposure significantly interfered with growth. The transcriptomic analysis found the molecular modifications in A. thaliana after the MB fumigation with the up-regulation of genes specifically relative to the abiotic and oxidative stress, and the down-regulation of auxin transporter genes. Some important gene expressions were verified by RT-qPCR and their expression patterns were similar. Oxidative stresses via the reactive oxygen species (ROS) in relation to MB phytotoxicity were confirmed with the increased malondialdehyde in MB-4h-treated A. thaliana. Uneven distribution of auxins via lower expression of auxin transporter genes was also determined using UPLC-ESI-QqQ MS. Application of two ROS scavengers such as N-acetyl-cysteine and L -glutathione minimized MB phytotoxic effect in A. thaliana. Therefore, MB caused severe oxidative stress, and alternatives regarding the use of MB should be considered.

Acrylic pressure-sensitive adhesives (PSAs) are used as fixatives between layers of a display. PSAs&rsquo, function is an important factor that determines the performance of the display. Of the various display types available, the touch screen panel (TSP) of smart devices is firmly related to the relative permittivity of the elementals. Therefore, adjusting the relative permittivity of the PSA is indispensable for driving the TSP. Accordingly, selected acrylic pre-polymers were polymerized and the pre-polymer was blended and cross-linked with monomers with different chemical structure to adjust the relative permittivity. The monomers were hexametyldisiloxane (HMDS), N-vinylcaprolactam (NVC), tert-butyl acrylate (TBA), and isooctadecyl acrylate (ISTA). The gel fraction and transmittance as a function of the monomers show a similar result to the pure acrylic PSA. However, the gel fraction value decreased to about 90% and the transmittance decreased to about 85%, due to the immiscibility between nonpolar HMDS and acrylic PSA. On the other hand, the adhesion properties were improved when NVC was added because of the polarity of the nitrogen group. In addition, the relative permittivity of the PSA decreased regardless of the monomer chosen. There was, however, a difference in the optimal content of each monomer, and NVC decreased from 4 phr content to about 3.4 in reducing relative permittivity. Through the above results, it was confirmed that NVC having a nitrogen group is most advantageous in lowering adhesion properties and relative permittivity, and necessitates further research based on the findings.

The susceptibility of Lasioderma serricorne to phosphine (PH3), ethyl formate (EF) and their combination (PH3 + EF) was evaluated in this study. Eggs, larvae, pupae and adults were subjected to treatment with fumigants to determine the 90% lethal concentration time (LCt90) values. Treatment with PH3 for 20 h resulted in LCt90 values of 1.15, 1.39, 14.97 and 1.78 mg h/L while treatment with EF resulted in values of 157.96, 187.75, 126.06 and 83.10 mg h/L, respectively. By contrast, the combination of PH3 + EF resulted in LCt90 values of 36.05, 44.41, 187.17 and 35.12 mg h/L after 4 h. These results show that, through treatment with PH3 + EF, control can be achieved at lower concentrations than for treatment with EF alone and at lower exposure times than for treatment with PH3 alone. The sorption rates of the fumigants on cured tobacco leaves were determined for filling ratios of 2.5%, 5.0% and 10.0% (w/v). Cured tobacco leaves were treated with either 2 mg/L PH3, 114 mg/L EF or 0.5 mg/L PH3 + 109 mg/L EF. Treatment with PH3 showed sorption rates of 0.0%, 7.1% and 14.3%. EF, however, showed higher sorption rates of 64.9%, 68.5% and 75.5%, respectively, for the indicated filling ratios. When PH3 and EF were combined, the sorption rate of PH3 was 0.0%, while the sorption rates of EF were lower (9.1%, 12.0% and 23.2%) than treatment with only EF. EF required a ventilation time of longer than 22 h to desorb from cured tobacco leaves. Therefore, PH3 + EF can effectively control L. serricorne in cured tobacco leaves, with sufficient ventilation time required after treatment for the safety of workers.

The Enzyme Linked Immunosorbent Assay (ELISA) technique has been widely used for the identification and quantification of biochemical markers. The typical ELISA requires a number of washing steps to eliminate the unbound proteins which sometimes cause the desorption of protein due to their weak bonding between protein and well plate. In this study, we have developed a meshed type of plastic membrane in order to increase the reliable binding efficiency between proteins and the membrane surface, and to provide easy steps of washing. The use of our developed solid membrane has significantly increased the binding capacity of the biomolecules because this membrane ELISA (mELISA) provides 3D binding surfaces which increases the surface area when compared to the conventional 2D surface well plate. The columns were pretreated to form a self-assembled layer (SAM) on the surface for the stable conjugation of a target antibody. The SAM-coated membranes could be stored for one month without any further deterioration of stability. The measured optical density (O.D.) shows a 1.2-fold increase in IgG antigen (25 &mu, g/mL) from the plastic membrane as compared with the conventional ELISA method. The concentrations of thyroid stimulating hormone were also monitored using the mELISA method and it shows good linearity against the concentrations.

In this study, we considered the toxicity of the combustion gases for the indoor floor materials such as carpet tiles, rubber tiles, decorated tiles, monorium, and PVC vinyl asbestos using the cone calorimeter and the NDIR analysis equipments. Only 5 types of gases (CO, , , NO and ) were selected to analyze among the combustion gases because of the limitations of NDIR equipment. For monorium the concentrations of , CO and were relatively higher and the maximum concentration of was 13 times higher than rubber tiles. Especially, the maximum concentration of CO was 3.09 times higher than PVC vinyl asbestos and it was 3.0~9.2 times higher than the permissible concentration of 50 ppm. For carpet tiles the concentration of NO was relatively higher and it was 2.9 times higher than rubber tiles. Also, the maximum concentration of was 2.25 times higher than PVC vinyl asbestos but it was lower than the hazardous concentration of 117~154 ppm. Therefore, the danger of and CO was considered to be much higher in fires with monorium.

Current clinical trials of new anticancer therapies against metastatic renal cell carcinoma (RCC), including molecular‐targeted therapies, have not shown promise. The purpose of this study was to preclinically assess the antitumor effects of MC‐4, a partially purified material of Artemisia annua L., as a monotherapy or in combination with the known mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, everolimus, against Caki‐1 (Von Hippel‐Lindau (VHL)+/+) and 786‐O (VHL−/−) human RCC cells. MC‐4 monotherapy significantly increased tumor growth inhibition and autophagic cell death in RCC cells in vitro and in vivo. Everolimus led to compensatory Akt activation by inhibiting only mTORC1 signaling pathway. In contrast to everolimus, MC‐4 enhanced phosphatase and tensin homolog expression and reduced its downstream effector, Akt/pyruvate kinase muscle isozyme M2 (PKM2), leading to decreased expression of glucose transporter 1, which is associated with cancer cell metabolism. The synergistic antitumor and anti‐metastatic effects induced by co‐administration of MC‐4 and everolimus involve cell growth inhibition and autophagic cell death via dual targeting of phosphatidylinositol 3‐kinase (PI3K)/Akt/PKM2 and mTORC1. These findings suggest that MC‐4 is a novel Akt/PKM2 inhibitor that can overcome the limitation of existing mTOR inhibitors and can be considered a novel strategy to treat patients with rapidly progressing advanced RCC.

The purpose of this study was to investigate the effect of bile salts on gastrointestinal absorption and the plasma second peak phenomenon of roxithromycin in rats. The pharmacokinetic parameters of roxithromycin were calculated after single oral administration at a dose of 20 mg/kg in sham-operated (control), bile duct cannulated (BDC) and bile salt co-administered bile duct cannulated (BSBDC) rats. In BDC rats, the total area under the plasma concentration–time curve from time zero to time infinity (AUC0–∞) and the peak plasma concentration (Cmax) were significantly smaller (0.572-fold) and lower (0.412-fold), respectively, than those in the control rats. These values were recovered by co-administration of bile salt (0.831- and 0.828-fold for AUC0–∞ and Cmax compared with the control, respectively). Thus, the decreased absorption of roxithromycin in BDC rats could be due to a depletion of bile. The solubility of roxithromycin was 3.09-fold increased at 30 mm of sodium taurocholate. The oral dosage regimen of roxithromycin could be changed in patients with bile deficiency or when the drug is administered to individuals on a high-fat diet, if the present rat data can be extrapolated to humans. Copyright © 2013 John Wiley & Sons, Ltd.

This study focuses on the identification of ignition characteristics and carbon discharge resulting from combustion of surface fuels vulnerable to forest fire. Four withered surface fuels, including dead leaves and cones of Pinus densiflora, dead leaves of Quercus variabilis, and Castenea crenata burs; and six biofuel herbs, including Agsstache rugosa, Oplismenus undulatifolius, Pueraria thunbergiana, Cirsium japonicum var. ussuriense, Festuca ovina L., and Osmundaceae were selected for analysis. Also, monthly carbon emissions (Jun. - Oct. 2008) from Festuca ovina were analyzed. As a result of tests, it was confirmed that dead leaves and cones of P. densiflora and C. crenata burs were instantly ignited with flame, which lasted quite a while. The total CO2 and CO emissions from the 10 different kinds of surface fuels analyzed on this study were 28-98 g and 0.76-4.08 g per 50 g of each fuel, respectively, indicating that the amount of carbon emissions vary depending on the type of fuel. The results also demonstrated that there is a great difference between withered fuels and biofuels in terms of carbon emissions. More specifically, the four withered types of fuels, compared to the six biofuel herbs, were found to emit more CO2 and CO. In particular, dead cones of P. densiflora emitted more carbon dioxide (CO2) and carbon monoxide (CO) than the rest of the surface fuels. Also, the carbon emissions were found high during the period of from August to September. Consequently, in the case of a forest fire, dead cones and leaves of P. densiflora are expected to emit up to 3.5 times more CO2 and CO than the other surface fuels. The area covered with dead leaves and pine cones is thought to have a high risk of ignition, high fire inten- sity because of relatively long lasting flame, and rapid fire spread. Herbs and living fuels with high moisture content are expected to elucidate the course of fire in that they produce large amount of combustion prod- ucts such as smoke and carbon discharge resulting from nonflame-ignition.

We report the fabrication and characterization of a planar resonant tunneling transistor (PRTT) using a GaAs/AlGaAs heterostructure wafer. Our PRTT operates as an enhancement-mode device, and shows the negative differential resistance (NDR) modulated with the gate bias in an extremely wide range (from the fully depleted dot to the dot in a single-electron transistor regime). This NDR spectrum represents a full, gate-bias-modulated evolution of the 0-D states in a quantum dot. Our data are also consistent with the ground (E 1) and the first excited state (E 2) of the Fock-Darwin states.

We present the results of a systematic study of chemical vapor deposition of graphene on silicon substrates. The silicon substrate is covered with SiO 2 and capped with an electron-beam evaporator deposited nickel film, which serves as the catalyst for carbon precursor decomposition. Methane is used as the carbon precursor. Three key parameters of CVD growths, the growth temperature, time, and the post-growth cooling rate are studied and the optimized combination of the three allowed for the reproducible fabrication of single layer graphene of larger than 100 μm 2 covering more than 50% of the surface of 1-in. diameter Si wafers. We further demonstrate the transfer of CVD graphene onto SiO 2 /Si surfaces with higher than 95% success rate. Our result together with those reported by other research groups shows real promise of the integration of carbon electronics with silicon integrated circuit technology.

Strain potentials, potential profiles, and electronic subband energies of InAs/GaAs coupled double quantum dots (QDs) were calculated by using a finite-difference method (FDM) taking into account shape-based strain effects. The shape of the InAs/GaAs coupled double QDs on the basis of the transmission electron microscopy image was modeled to be a truncated hemi-ellipsoid. The interband transition energies from the ground electronic subband to the ground heavy-hole band (E1-HH1) in the InAs/GaAs coupled double QDs, as determined from the FDM calculations taking into account strain effects, were in qualitatively reasonable agreement with the excitonic peaks corresponding to the (E1-HH1) interband transition energies at several temperatures, as determined from the temperature-dependent photoluminescence spectra. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Strained potential profiles and electronic subband energies of InAs/GaAs coupled double quantum dots (DQDs) were calculated by using a three-dimensional finite-difference method (FDM) taking into account shape-based strain and nonparabolic effects. The interband transition energies from the ground electronic subband to the ground heavy-hole band (E 1 -HH 1 ) in the InAs/GaAs DQDs, as determined from the FDM calculations taking into account strain and nonparabolic effects, were in reasonable agreement with the experimental peaks corresponding to the (E 1 -HH 1 ) interband transition energies at several temperatures, as determined from the temperature-dependent photoluminescence spectra.

Two types of secondary amino alcohols were successfully resolved on a liquid chromatographic chiral stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid. The secondary amino alcohols containing a secondary amino group connected directly to the stereogenic center were resolved much better than those containing a hydroxyl group attached directly to the stereogenic center. In addition, the dependence of the separation factor (α) on column temperature was exactly opposite for the two different types of secondary amino alcohols. From the thermodynamic calculations based on Van’t Hoff plots, we conclude that the enantioselectivity for the resolution of the secondary amino alcohols containing a secondary amino group connected directly to the stereogenic center is enthalpically controlled while that for the resolution of the secondary amino alcohols containing a hydroxyl group attached directly to the stereogenic center is entropically controlled.

Post-growth rapid thermal annealing (RTA) has been used to investigate an interdiffusion and the structural change in an InGaAs dots-in-a-well (DWELL) structure grown by molecular beam epitaxy using an alternately supplying InAs and GaAs sources. In the case of the as-grown sample, which has a metastable quantum structure due to an intentional deficit of source materials, it is found that an InGaAs quantum well (QW) coexists with the premature quantum dots (QDs), and an intermediate layer exists between the QW and the QDs. Through the RTA process at 600 and 800°C for 30s, metastable structure changes into a normal DWELL structure composed of QDs and QW as a result of the intermixing of premature QDs and the intermediate layer.

We have investigated the electrical and optical properties of the modulation-doped InAs quantum dots (QDs) by alternately supplying In and As sources. Three different samples are fabricated according to the doping concentration of the Si-doped GaAs layer. All the samples show the excited state emissions as well as the ground state emission in photoluminescence (PL) spectra due to the state filling by the electrons supplied from the doped GaAs layer. For a low doping concentration the transition from the first excited electron state to the first excited hole state (E1–H1) is apparent together with the ground state transition (E0–H0). These PL emissions increase with the similar rate as the excitation power density increases. For higher doping concentrations the ground state transition and the transition from the first excited electron state to the ground hole state (E1–H0) are apparent at a low excitation power density. As the excitation power density increases, the E1–H1 transition becomes dominant rather than the E1–H0 transition. In the capacitance-voltage (C–V) result for the sample with a low doping concentration, the characteristic steps due to the accumulation of electrons are observed. For the sample with higher doping concentrations the characteristic step is not found in C–V curves, which is associated with the state filling of QDs.

We report on the ferromagnetic characteristics of Zn 1− x Mn x O films ( x =0.1–0.3) prepared by the sol–gel method on silicon substrates using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry at various temperatures. Magnetic measurement show that the Curie temperature ( T C ) and the coercive field ( H C ) were ∼39 K and ∼2100 Oe for the film of x =0.2, respectively. EDS and TEM measurements indicate that Mn content at the interface is significantly higher than that at the center of the Zn 0.8 Mn 0.2 O film showing the ratio, Zn:Mn:O≅1:12:15. This experimental evidence suggests that ferromagnetic precipitates containing manganese oxide may be responsible for the observed ferromagnetic behavior of the film.

We investigated the electrical and optical properties of InGaAs self-assembled quantum dots grown using the atomic layer epitaxy (ALE) technique. Dots–in–a–well structures were grown by alternately supplying InAs and GaAs sources on an InGaAs layer and covering with another InGaAs layer. Three samples produced with different numbers of cycles of alternate InAs/GaAs supply were characterized by capacitance-voltage and photoluminescence (PL) measurements. For the ten cycle dots–in–a–well structure, a strong zero-dimensional electron confinement was observed even at room temperature. On the other hand, for the five-cycle structure, the PL results indicate that the InGaAs quantum well structure coexists unstably with premature quantum dots. By comparing the results for samples with different numbers of cycles, we suggest that an ALE dots–in–a–well structure can be formed by the aggregation of In and Ga atoms incorporated into the InGaAs quantum well layer when the number of cycles exceeds the critical number ...

We report on the annealing effect and ferromagnetic characteristics of ZnMnO film prepared by sol-gel method on the silicon (100) substrate using field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry. Magnetic measurements show thatZnMnO films exhibit ferromagnetism at 5 K revealing the coercive field of ∼110 Oe for as grown sample and 360, 1035 Oe for samples annealed at 700, 800 , respectively. Our experimental evidence suggests that ferromagnetic precipitates of a manganese oxide may be responsible for the observed ferromagnetic behaviors of the film.he film.

Superparamagnetic properties of self-aggregated cobalt nanoparticles in the perfluorinated sulfo-cation membrane (MF-4SK) prepared by ion-exchange method were investigated by transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometry at various temperatures. Our experimental results show that cobalt nanoparticles in MF-4SK exhibit superparamagnetic properties above the blocking temperature ( T B ), which varies from ∼80 to ∼300 K depending on the cobalt concentration at 100 Oe applied field. The average particle radius of 3.8 nm inferred from Langevin function fit for the concentration of 7.8×10 19 cobalt atoms per 1 g of polymer film is in good agreement with TEM observation. This experimental evidence suggests that cobalt nanoparticles in the polymer film obey a single-domain theory. The results are discussed in the light of current theory for the superparamagnetic behavior of magnetic nanoparticles.

GaN micro-crystals have been synthesized by the direct reaction of NH3 with Ga-melt. The dark-gray colored GaN micro-crystals were obtained through the synthesis process at 1050°C for 3 h in atmospheric NH3 ambient gas. In particular, the characteristics of the GaN micro-crystals obtained from a catalytic reaction with metallic Ni and Ti powders of 0.1 mol% were investigated using XRD, PL and SEM. It was found that the addition of Ni powder in the Ga-melt resulted in the decrease of the product yield but the increase of the PL peak intensity, and the controlled reduction of the crystallite size.

We have investigated the alignment of self-assembled InAs quantum dots (QDs) using the strained InxGa1−xAs/GaAs superlattice system in which we can control the strain field precisely. Through the estimation of critical thickness of strained layer, an in situ alignment of quantum dots is obtained along 〈1 1 0〉 direction on the controlled strained layer. The anisotropic alignments along [1 1 0] and [ 1 1 0 ] directions are closely related with the anisotropy of strain-relief for both directions, which affect the anisotropic diffusivity of indium adatoms on the strained superlattice layer. The strong alignment appears on the highly strained layer, resulting in the formation of chained quantum dots. These results indicate that aligned InAs quantum dots formed by changing the periods of strained superlattice hold promise for potential applications in nanoelectronic devices, such as single electron tunneling devices.

We have investigated an oxygen gas-pulsed plasma in conjunction with the enhancement of atomic oxygen radical O* flux and its application. The measured mean O* flux of 5.9×1015 atoms/cm2 s from the gas-pulsed plasma with a duty cycle of 50% (periodically opened for 0.3 s and closed for 0.3 s) at 32 sccm is 1.6 times enhanced compared to that of a continuous wave plasma and is in good agreement with the increment obtained with the time averaged value of transient optical emission profiles of O* at 777.6 nm. The generation of a higher O* flux was interpreted by the mitigation of a recombinative reaction process through the interruption of gas flow injections in the gas pulsed plasma. As a preliminary application, an increase in critical temperature of superconducting YBa2Cu3O7−x thin films was achieved by the gas-pulsed plasma oxidation with a duty cycle of 50%.

The dependences of Cr 2+ and Cr 3+ electron paramagnetic resonance (EPR) signals as a function of Cr concentration have been investigated in conjunction with clarifying the atomic configuration for obtaining semi-insulating properties in a vertical gradient freeze (VGF)-GaAs single crystal codoped with Cr and In (VGF-GaAs:Cr,In). Cr 2+ EPR signals are observed in both samples of semi-insulating and semiconducting GaAs:Cr,In single crystals, whereas Cr 3+ EPR signals can be observed only in semi-insulating samples. The semi-insulating properties become obvious when increasing the intensity of Cr 3+ and Cr 2+ EPR signals in VGF-GaAs:Cr,In crystals. Isolated Cr Ga 3+ ions play an important role in GaAs as a charge compensation center for obtaining semi-insulating property.

Objective: The aim of this study was to compare new bone formation with titanium (Ti) surface and hydroxyapatite (HA)-coated titanium surface in mucosal perforation model. Materials and Methods: HA coating to the Ti disc and implant were done by aerosol deposition technique. Alkaline phosphatase assay and cell migration assay were done in Ti and HA surface disc with MG63 cells. For the in vivo test, 5 New Zealand white rabbits were used. Two penetration defects were prepared in the nasal bone. Subsequently, 2 types of implants were installed into the defect (diameter: 3.0 mm, length: 6.0 mm). Approximately 5.0 mm of the fixture’s surface penetrated into the nasal cavity. In the experimental group, HA-coated implants were used. The same design of implants without coating was used in the control group. The animals were sacrificed 8 weeks postoperatively. Subsequently, a histomorphometric analysis was done. Results: Alkaline phosphatase activity was significantly higher in HA-coated surface than in titanium surface (P G 0.05). In addition, more cells were migrated into the HA-coated surface when compared to Ti surface. In the animal experiments, mean new bone formation was 30.68 T 14.16% in the experimental group and 6.92 T 5.12% in the control group (P = 0.001). Mean bone-to-implant contact was 31.71 T 8.41% in the experimental group and 7.98 T 5.58% in the control group (P G 0.001). Mean height of the bone regeneration was 3.70 T 0.76 mm in the experimental group and 1.04 T 0.67 mm in the control group. The difference between the 2 groups was statistically significant (P G 0.001). Conclusions: HA-coated implants exhibited more bone regeneration in the mucosal penetration model than the uncoated implants.

Transient optical emission characteristics of a nitrogen gas‐pulsed electron cyclotron resonance (ECR) plasma have been investigated as a first step towards understanding the nature of a nitrogen gas‐pulsed plasma. We observed different transient optical emission profiles for the first negative N+2, the second positive N2*, and the first positive N2* emission bands in nitrogen gas‐pulsed ECR plasma that are closely related to the pressure changes in a discharge cavity of the plasma source. On the basis of the transient emission profiles, optical emission spectra over the wavelength range 300–700 nm were obtained for three specific time regions within the pulse. During the gas‐pulsed injection period large ratios of N2*/N+2 (2.5–7.1) and low electron temperatures (1.2 eV) were observed. On the other hand, small ratios of N2*/N+2 (0.3) and high electron temperature (2.5 eV) were recorded 0.65 s after stopping the gas‐pulsed injection. These observed N2*/N+2 ratios are interpreted in terms of different excit...

The effects of the axial magnetic field on the growth striations of vertical gradient freeze GaAs have been studied. It is shown that the application of an axial magnetic field can afford to a perfect single crystal without any twin formations. For the crystal with zero magnetic field, the striations are irregularly spaced in the conical region and are mainly dependent on irregular facet evolutions. However, the growth interface becomes straighter and flatter compared to that of the crystal with B = 0 when the magnetic flux density is increased to 1200 G. Irregularities of the facet evolution existing in the conical region of the crystal with zero magnetic field are almost eliminated by the application of an axial magnetic field.

The growth behavior of GaAs AlGaAs during metalorganic chemical vapor deposition (MOCVD) on V-grooved GaAs(311)A substrates, specifically its dependence on growth temperature and V III ratio, has been investigated. A new (100) facet has evolved at the outer edge of the short side wall of the groove. The length of this facet decreases with increasing the growth temperature and reducing the V III ratio. The phenomena can be explained by the surface mobility or incorporation rate dependence of group III species on each facet as it appeared in this study. The best surface morphology has been obtained at 750°C. The newly evolved (100) facet has a defect free surface. Photoluminescence (PL) measurements have been carried out after growing 2 kinds of GaAs quantum wells (QWLs) on the patterned (311)A substrates. In the case of QWLs with a thick AlGaAs buffer layer, 3 peaks from the (100), (433)A and (311)A planes have been identified, while the (100) peak was not detected in the case of a thin buffer layer.

Nanostructured silicon was formed by means of the ionized N2 gas reaction on SiO2/Si, and the electronic structure, surface morphology, and optical properties were investigated. The physicochemically modified thin layers were resolved to SiNy and SiOxNy through the observation of Si 2p, O 1s, and N 1s core-level spectra in x-ray photoelectron spectroscopy. The formations of SiOxNy and SiO2 nanostructures (3–4 nm in size), performed by the etching process followed by adsorption of ionized nitrogen, were confirmed by atomic force microscopy. The nanocrystalline Si (6 nm in size) distributed within the modified layer (approximately 10 nm thick) was observed after the in situ rapid thermal annealing processes, using high-resolution transmission electron microscopy. Photoluminescence with a wavelength peaking at around 400 nm was emitted from the nanocrystalline Si formed from the SiOxNy/SiO2/Si structures. This work suggests that the nanocrystalline-Si formation and the nanostructured surface modification met...

The deposition rate of tungsten selectively prepared by hydrogen reduction of WF6 was measured, and the encroachment produced by inherent silicon reduction even in the presence of H2 gas was examined by cross-sectional TEM and SEM. In the WF6-H2 system, the degree of encroachment is not explained by the Si reduction reaction alone, but is rather related to the Si reduction time decreasing with increasing deposition rate of H2-reduced tungsten film, because a blocking layer is formed above the Si-reduced tungsten. This results in a lesser degree of encroachment. Consequently a high deposition rate of H2-reduced tungsten can decrease the degree of encroachment. By calculation, a thickness of 6.8–13.3 nm is necessary for H2-reduced tungsten to prevent WF6 gas from reacting with Si.

A new HZM (horizontal zone melt) grower, using DMF (direct monitoring furnace) with a CCD camera which can provide the in-situ observations of the entire growth procedure as well as the liquid-solid interface, has been developed. Through the HZM technique, a higher yield of the GaAs: In single crystal with low dislocation and good uniformity along the growth direction was obtained. In-situ observation technique of the interface shape during the growth may be applicable to the growth of high quality crystals reproducibly. We confirmed that the incorporation of indium in the crystal has better uniform distribution along the growth axis and the required doping concentration for initiating the “hardening effect” was about 2 × 10 19 cm -3 in our growth technique. The electrical uniformity along the growth axis with maximum deviation value of 13% is comparable to that found in most crystals grown by normal freezing method.

We have investigated the humidity and depurination (creating apurinic sites) effects on the electrical conduction in the λ-DNA films at different relative humidities and depurination times. The DNA films were found to follow the polaron hopping model, and the polaron hopping distance turned out to decrease at the higher relative humidity, more water molecules supposedly being adsorbed on the film. The activation energy showed little dependence on the depurination time at the higher relative humidity, whereas at the lower humidity it increased sharply with increasing depurination time.

We report on the selective formation of InGaAs quantum dots (QDs) by molecular beam epitaxy. Nanoscale patterned Ga2O3 thin film deposited on the GaAs (100) substrate was employed as a mask material. Due to the enhanced migration effect of the group-III adatoms, such as Ga and In on Ga2O3 mask layer, the InGaAs QDs formed on the patterned substrate results in coalesced islands unlike those formed on the nonpatterned substrate. The estimation of the relative volume of the islands per unit area revealed that the desorption process as well as the migration of the Ga and In adatoms might occur on the Ga2O3 layer during the growth process, providing a good selective growth of self-assembled QDs.

We have studied the in situ modification of coherently grown InGaAs dots by interaction with phosphorus. By monitoring the intensity of reflection high-energy electron diffraction transmission spot, the in situ phosphorus (precracked PH3) supply on the InGaAs dots was examined at 480 °C. It was found that the phosphorus exposure induces a surface structure change from a dot structure to a flat surface. The change is caused by the replacement of arsenic in the dots by phosphorus, which reduces the strain between the InGaAs(P) dots and the GaAs substrate. By switching AsH3/PH3 beams in situ, a reversible transition of the surface structure between the InGaAs dot structure and the InGaAsP flat surface was observed. A transitional state between the dot structure and the flat surface was metastabilized by tuning the AsH3/PH3 beam ratio. The metastabilized surface was observed ex situ using a high-resolution scanning electron microscope.

We investigated the effects of carrier dynamics on the temperature dependence of the photoluminescence (PL) of an InGaAs dots-in-a-well (DWELL) structure. The quantum dots (QDs) were formed by the atomic layer epitaxy (ALE) technique alternately supplying InAs and GaAs sources. It was found from the PL measurements at various temperatures that the DWELL structure was accomplished through the generation process of the intermediate layer between the quantum well (QW) and the QDs during the formation of the QDs inside a QW. The thermal quenching equations on the basis of the rate equation model can be explained by the carrier dynamics, which included in the radiative recombination, the carrier thermal escape and the carrier capture process occurring in these three layers, i.e. QW, QD and the intermediate layer.

In this article, we report the spin-valve effect in a lateral spin-injection device with an FM/Si/FM structure.

Effects of sulfur and hydrogen passivation on the thermal stability of RuO2 Schottky contacts on n‐type GaAs have been studied by treatments with (NH4)2Sx solution and hydrogen plasma, respectively. The RuO2 thin films were deposited by dc magnetron sputtering using a Ru target and a mixture of argon and oxygen gases. The thermal stability of RuO2 Schottky contacts during thermal annealing in the temperature range from 200 to 550 °C for 10 min was investigated by current‐voltage (I–V) measurements and Auger electron spectroscopy. For the sulfur treated sample, the ideality factor was constant at about 1.01 in the whole temperature range and the barrier height of 0.84 eV was maintained up to 350 °C. Hydrogenation treatment, however, was not so effective in preventing the thermal degradation compared to the sulfurization process. It is confirmed that the effective sulfur passivation to enhance the thermal stability of RuO2/GaAs is responsible for the suppression of an oxidation in the interface between GaAs...

We have observed a well‐defined Cr3+(3d3) electron paramagnetic resonance signal at 4 K in vertical gradient freeze semi‐insulating GaAs single crystal through a co‐doping with Cr and In. On the basis of analyzing the rotation pattern of the Cr3+ center, the z‐axis of the D‐tensor for Cr3+ center in the principal axis system was found to be parallel to the [110] direction in the crystal. The g tensor and zero field splitting parameters are determined with monoclinic spin Hamiltonian. The local site symmetry of the Cr3+ center in GaAs:Cr, In is different from that reported in GaAs:Cr. The lowering of the substitutional Cr3+ at Ga site in symmetry from cubic (Td) to monoclinic field (C2) seems to be attributed to the change of the local field due to an In atom existed in the 2nd nearest neighbor.

Self-assembled quantum dots (SAQD) utilizing a Stranski-Krastanow growth mode are attractive because they are easily formed defect-free compared to other fabrication methods, but it is difficult to control the size and the position of QDs. Recently, preferential alignment of the QDs along the multiatomic steps, which were formed on a 2/spl deg/-off(100) GaAs substrate was reported. This method is attractive because it is a kind of in-situ process without using physical constraints such as dielectric masks and patterns. The size of QDs on 2/spl deg/-off(100) GaAs substrate is normally less than the terrace widths. The terrace width of 2/spl deg/-off(100) GaAs substrate is transformed by bunching effect mainly due to Ga diffusion during the growth. In particular, the terrace widths increase as increasing the growth thickness of GaAs buffer layer. In this work, we have investigated the dependence of GaAs buffer layer on the distribution of InAs QDs grown on 2/spl deg/-off(100) GaAs substrate.

We have investigated the selective formation of InxGa1-xAs quantum dots by molecular beam epitaxy. Particularly, we report on selectivity formed InxGa1-xAs QDs on the GaAs(100) substrate with fine- patterned oxide layers such as gallium oxide and silicon oxide, which are prepared with electron bema lithography technique. The electron beam lithography pre-patterned oxide layers were used to assemble the dots in a specific region. Both of the oxide layers served as mask materials were compared for the better selective growth of self-assembled QDs. The migration and the desorption of the In and Ga adatoms on the oxide layers are considered to be the most important factors for the selective formation of InxGa1-xAs quantum dots by molecular beam epitaxy. The influences of the mole fractions of indium, the growth temperature and the growth interruption times on the morphological transformation from 2D to 3D structures were discussed. Particularly, the 2D arrays of quantum dots selectively formed on GaAs substrates with pre-patterned Ga2O3 oxide layer may eventually be used for novel electronic or optical devices.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this work, we report on the selective formation of the InAs quantum dot arrays using the Ga2O3 thin film as a mask material with molecular beam epitaxy technique. Atomic force microscopy(AFM) and scanning electron microscopy( SEM) measurement was carried out to characterize the QDs formed selectively on the patterned Ga2O3 substrate.

With carbon tetrabromide (CBr/sub 4/) and carbon tetrachloride (CCl/sub 4/) supplied, well-defined selective GaAs epilayers were successfully grown on V-groove and mesa patterned GaAs substrates by one-step atmospheric pressure metalorganic chemical vapor deposition. It appeared that the selectivity of the grown epilayers showing huge lateral growth rate enhancement depended on supplying gases. Inside a V-groove, the selectively grown GaAs epilayers exhibited a triangular and a round shape with supplying CBr/sub 4/ and CCl/sub 4/, respectively. The selective growth was also done on the side walls of a mesa. In contrast, no growth was observed outside V-groove and on the top of the mesa. This kind of selective epitaxial technology has promising features for well-defined quantum structures and lateral p-n junction.

Diffuse x-ray reflectivity intensities were measured to characterize interface morphologies of Mo/Si multilayers with and without interleaved carbon thin layers. Parameters related to the interface morphologies can be obtained by fitting the measured intensities within the distorted wave Born approximation in such a way that intermixing widths of graded interfaces, correlated interface roughness amplitudes and vertical correlation lengths are obtained. The interface parameters of Mo/Si and Mo/C/Si/C multilayers are compared for as-grown samples and annealed ones.