• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.313-313
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• 2012

In recent years there have been many studies of InGaN/GaN based light emitting diodes (LEDs) in order to progress the performance of luminescence. Many previous literatures showed the performance of LEDs by changing the LED structures and substrates. However, the studies carried out by the researchers so far were very complicated and sometimes difficult to apply in practice. Therefore, we propose one simple method of changing the thickness and the numbers of multiple quantum wells (MQWs) in order to optimize their effects. In our research, we investigated electrical and optical properties by changing the well thickness and the number of quantum well (QW) pair in LED structures by growing the structure -inch Si (111) wafer. We defined the samples from LED_1 to LED_3 according to MQW structure. Samples LED_1, LED_2 and LED_3 consist of 5-pair InGaN/GaN (3.5 nm/ 4.5 nm), 5-pair InGaN/GaN (3 nm/4.5 nm) and 7-pair InGaN/GaN (3.5 nm/4.5 nm), respectively. We characterized electrical and optical properties by using electroluminescence (EL) measurement. Also, Efficiency droop was analyzed by calculating external quantum efficiency (EQE) with varying injection current. The EL spectra of three samples show different emission wavelength peaks, FWHM and the blueshift of wavelength caused by screening the internal electric field because of the effect of different MQW structure. The results of optical properties show that the LED_2 sample reduce the internal electric field in QW than LED_1 from EL spectra. the increase in the number of QW pairs reduces the strain and increase the In composition in MQW. And, the points of efficiency droop's peak show different trend from LED_1 to LED_3. It is related with the carrier density in active region. Thus, from the results of experiments, we are able to achieve high performance LEDs and a reduction of efficiency droop and emission wavelength blueshift by optimizing MQWs structure.

• Korean Journal of Materials Research
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• v.27 no.11
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• pp.631-635
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• 2017

We report facile solution processing of mesoporous hematite (${\alpha}-Fe_2O_3$) thin films for high efficiency solar-driven water splitting. $Fe_2O_3$ thin films were prepared on fluorine doped tin oxide(FTO) conducting substrates by spin coating of a precursor solution followed by annealing at $550^{\circ}C$ for 30 min. in air ambient. Specifically, the precursor solution was prepared by dissolving non-toxic $FeCl_3$ as an Fe source in highly versatile dimethyl sulfoxide(DMSO) as a solvent. The as-deposited and annealed thin films were characterized for their morphological, structural and optical properties using field-emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and UV-Vis absorption spectroscopy. The photoelectrochemical performance of the precursor (${\alpha}-FeOOH$) and annealed (${\alpha}-Fe_2O_3$) films were characterized and it was found that the ${\alpha}-Fe_2O_3$ film exhibited an increased photocurrent density of ${\sim}0.78mA/cm^2$ at 1.23 V vs. RHE, which is about 3.4 times higher than that of the ${\alpha}-FeOOH$ films ($0.23mA/cm^2$ at 1.23 V vs. RHE). The improved performance can be attributed to the improved crystallinity and porosity of ${\alpha}-Fe_2O_3$ thin films after annealing treatment at higher temperatures. Detailed electrical characterization was further carried out to elucidate the enhanced PEC performance of ${\alpha}-Fe_2O_3$ thin films.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.3 s.345
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• pp.1-8
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• 2006

In this paper, reliability (HCI, NBTI) and device performance of nano-scale CMOSFETs with different channel stress were investigated. It was shown that NMOS and PMOS performances were improved by tensile and compressive stress, respectively, as well known. It is shown that improved device performance is attributed to the increased mobility of electrons or holes in the channel region. However, reliability characteristics showed different dependence on the channel stress. Both of NMOS and PMOS showed improved hot carrier lifetime for compressive channel stress. NBTI of PMOS also showed improvement for compressive stress. It is shown that $N_{it}$ generation at the interface of $Si/SiO_2$ has a great effect on the reliability. It is also shown that generation of positive fixed charge has an effect in the NBTI. Therefore, reliability as well as device performance should be considered in developing strained-silicon MOSFET.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.165-171
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• 2016

In this study, the characterization of projects and analysis of R&D products and commercialization performances were done to serve some implications on the policy decisions related to the commercialization of R&D in marine and fisheries sector. A total of 212 R&D projects with 144 ones for marine and 68 for fisheries performed for 5 years, from 2010 to 2014, were sorted and analyzed on the respect of government budget, main performing body, and research period. The R&D result and commercialization performance were substituted to quantitative indicators, such as the number of published papers, the number of patents, the amount of the technology royalty, the number of technology transfers, and the improvement of public service, which were subjects to be analysed. Based on the results, this study suggests the policy implications for the success of national R&D program; 1) diversifying the main performing body, 2) operating the system for sharing research infrastructures among researchers, 3) introducing the adaptable R&D program management, 4) expending the portion of grants without detailed requests for proposal, and 5) leaning the investigation of R&D budgets on projects focusing on the practicalization and commercialization.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.89-94
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• 2006

Nafion/poly(ether(amino sulfone)) acid-base blend polymer electrolyte membranes were prepared and their proton conductivity and dimethyl ether permeability were investigated. Characteristics of direct dimethyl ether fuel cell (DDMEFC) performance using prepared blend membrane were studied. The increase of amine groups in the base polymer in composite membranes resulted in the decrease in dimethyl ether permeability. The proton conductivity of the blend membranes gradually increased as increasing temperature. The conductivity of Nafion/PEAS-0.6 (85:15) blend membranes was measured to be $1.42\times10^{-2}S/cm\;at\;120^{\circ}C$ which was higher than that of the recast Nafion. The performance of direct dimethyl ether fuel cell (DDMEFC) using the Nafion/PEAS blend membranes was higher than that using $Nafion^(R)115$ membrane. Enhanced performance of direct dimethyl ether fuel cells using Nafion/PEAS blend membrane was explained by reducing dimethyl ether (DME) crossover through the electrolyte membrane and maintenance of the proton conductivity at high temperature.

• Journal of Animal Science and Technology
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• v.64 no.1
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• pp.52-69
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• 2022

Ferulic acid (FA) is a phytochemical with various bioactive properties. It has recently been proposed that due to its phytogenic action it can be used as an alternative growth promoter additive to synthetic compounds. The objective of the present study was to evaluate the growth performance, carcass traits, fiber characterization and skeletal muscle gene expression on hair-lambs supplemented with two doses of FA. Thirty-two male lambs (n = 8 per treatment) were individually housed during a 32 d feeding trial to evaluate the effect of FA (300 and 600 mg d^-1) or zilpaterol hydrochloride (ZH; 6 mg d^-1) on growth performance, and then slaughtered to evaluate the effects on carcass traits, and muscle fibers morphometry from Longissimus thoracis (LT) and mRNA abundance of β₂-adrenergic receptor (β₂-AR), MHC-I, MHC-IIX and IGF-I genes. FA increased final weight and average daily gain with respect to non-supplemented animals (p < 0.05). The ZH supplementation increased LT muscle area, with respect to FA doses and control (p < 0.05). Cross-sectional area (CSA) of oxidative fibers was larger with FA doses and ZH (p < 0.05). Feeding ZH increased mRNA abundance for β₂-AR compared to FA and control (p < 0.05), and expression of MHC-I was affected by FA doses and ZH (p < 0.05). Overall, FA supplementation of male hair lambs enhanced productive variables due to skeletal muscle hypertrophy caused by MHC-I up-regulation. Results suggest that FA has the potential like a growth promoter in lambs.

• Journal of Powder Materials
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• v.30 no.4
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• pp.324-331
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• 2023

Lithium (Li) is a key resource driving the rapid growth of the electric vehicle industry globally, with demand and prices continually on the rise. To address the limited reserves of major lithium sources such as rock and brine, research is underway on seawater Li extraction using electrodialysis and Li-ion selective membranes. Lithium lanthanum titanate (LLTO), an oxide solid electrolyte for all-solid-state batteries, is a promising Li-ion selective membrane. An important factor in enhancing its performance is employing the powder synthesis process. In this study, the LLTO powder is prepared using two synthesis methods: sol-gel reaction (SGR) and solid-state reaction (SSR). Additionally, the powder size and uniformity are compared, which are indices related to membrane performance. X-ray diffraction and scanning electron microscopy are employed for determining characterization, with crystallite size analysis through the full width at half maximum parameter for the powders prepared using the two synthetic methods. The findings reveal that the powder SGR-synthesized powder exhibits smaller and more uniform characteristics (0.68 times smaller crystal size) than its SSR counterpart. This discovery lays the groundwork for optimizing the powder manufacturing process of LLTO membranes, making them more suitable for various applications, including manufacturing high-performance membranes or mass production of membranes.

• Journal of electromagnetic engineering and science
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• v.6 no.2
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• pp.135-145
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• 2006

This paper presents the theory, design, fabrication and characterization of the novel low actuation voltage capacitive shunt RF-MEMS switch using a corrugated membrane with HRS MEMS packaging. Analytical analyses and experimental results have been carried out to derive algebraic expressions for the mechanical actuation mechanics of corrugated membrane for a low residual stress. It is shown that the residual stress of both types of corrugated and flat membranes can be modeled with the help of a mechanics theory. The residual stress in corrugated membranes is calculated using a geometrical model and is confirmed by finite element method(FEM) analysis and experimental results. The corrugated electrostatic actuated bridge is suspended over a concave structure of CPW, with sputtered nickel(Ni) as the structural material for the bridge and gold for CPW line, fabricated on high-resistivity silicon(HRS) substrate. The corrugated switch on concave structure requires lower actuation voltage than the flat switch on planar structure in various thickness bridges. The residual stress is very low by corrugating both ends of the bridge on concave structure. The residual stress of the bridge material and structure is critical to lower the actuation voltage. The Self-alignment HRS MEMS package of the RF-MEMS switch with a $15{\Omega}{\cdot}cm$ lightly-doped Si chip carrier also shows no parasitic leakage resonances and is verified as an effective packaging solution for the low cost and high performance coplanar MMICs.

• Analytical Science and Technology
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• v.18 no.2
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• pp.130-138
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• 2005

Volatile organic compounds (VOCs) have been recognized as major contributor to air pollution. Catalytic oxidation in VOCs can give high efficiency at low temperature. In this study, monometallic Pt, Ir and bimetallic Pt-Ir were supported to $TiO_2$. Xylene, toluene and methyl ethyl ketone (MEK) were used as reactants. The monometallic or bimetallic catalysts were prepared by the excess wetness impregnation method and characterized by XRD, XPS and TEM analysis. Result reveal that Pt catalyst has higher conversion than Ir catalyst and Pt-Ir bimetallic catalysts. The existence of multipoint actives in, Pt-Ir bimetallic catalysts gives improved performance for the Pt metalstate. Bimetallic catalysts have higher conversion for VOCs than monometallic ones. The addition, VOCs oxidation follows first order kinetics. The addition of small amount of Ir to Pt promotes oxidation conversion of VOCs.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.