• Title/Summary/Keyword: growth reaction

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Epitaxial growth of yttrium-stabilized HfO$_2$ high-k gate dielectric thin films on Si

  • Dai, J.Y.;Lee, P.F.;Wong, K.H.;Chan, H.L.W.;Choy, C.L.
    • Electrical & Electronic Materials
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    • v.16 no.9
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    • pp.63.2-64
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    • 2003
  • Epitaxial yttrium-stabilized HfO$_2$ thin films were deposited on p-type (100) Si substrates by pulsed laser deposition at a relatively lower substrate temperature of 550. Transmission electron microscopy observation revealed a fixed orientation relationship between the epitaxial film and Si; that is, (100)Si.(100)HfO$_2$ and [001]Si/[001]HfO$_2$. The film/Si interface is not atomically flat, suggesting possible interfacial reaction and diffusion, X-ray photoelectron spectrum analysis also revealed the interfacial reaction and diffusion evidenced by Hf silicate and Hf-Si bond formation at the interface. The epitaxial growth of the yttrium stabilized HfO$_2$ thin film on bare Si is via a direct growth mechanism without involoving the reaction between Hf atoms and SiO$_2$ layer. High-frequency capacitance-voltage measurement on an as-grown 40-A yttrium-stabilized HfO$_2$ epitaxial film yielded an dielectric constant of about 14 and equivalent oxide thickness to SiO$_2$ of 12 A. The leakage current density is 7.0${\times}$ 10e-2 A/$\textrm{cm}^2$ at 1V gate bias voltage.

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WELL-POSEDNESS AND ASYMPTOTIC BEHAVIOR OF PARTLY DISSIPATIVE REACTION DIFFUSION SYSTEMS WITH MEMORY

  • Vu Trong Luong;Nguyen Duong Toan
    • Bulletin of the Korean Mathematical Society
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    • v.61 no.1
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    • pp.161-193
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    • 2024
  • In this paper, we consider the asymptotic behavior of solutions for the partly dissipative reaction diffusion systems of the FitzHugh-Nagumo type with hereditary memory and a very large class of nonlinearities, which have no restriction on the upper growth of the nonlinearity. We first prove the existence and uniqueness of weak solutions to the initial boundary value problem for the above-mentioned model. Next, we investigate the existence of a uniform attractor of this problem, where the time-dependent forcing term h ∈ L2b(ℝ; H-1(ℝN)) is the only translation bounded instead of translation compact. Finally, we prove the regularity of the uniform attractor A, i.e., A is a bounded subset of H2(ℝN) × H1(ℝN) × L2µ(ℝ+, H2(ℝN)). The results in this paper will extend and improve some previously obtained results, which have not been studied before in the case of non-autonomous, exponential growth nonlinearity and contain memory kernels.

Synthesis of SiC Nanotube by CNT-confined Reaction (CNT-confined reaction에 의한 탄화규소 나노튜브의 합성)

  • Rho Dae-Ho;Kim Jae-Soo;Byun Dong-Jin;Yang Jae-Woong;Kim Na-Ri
    • Korean Journal of Materials Research
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    • v.14 no.3
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    • pp.175-180
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    • 2004
  • SiC nanotubes were synthesized by CNT-confined reaction. Evaporated SiO gas reacted with carbon nanotubes by VS growth mechanism. By confineded reaction, carbon nanotube was changed to SiC nanotube, and synthesized SiC nanotube was filled partly by the gas reaction in the nanotubes. SiC nanotube's mean diameters were not changed than carbon nanotubes because of means ratio of $CO_2$ and SiO gas was maintained evenly during the process. This result was same of data of simulation. By TEM observastion, SiC nanotube was filled by reaction of inner wall of CNT and SiO gas through the VS reactions. Converted SiC nanotube's compositions were revealed Si and C of 1: 1 ratios at all sites of nanotube by EDS.

A Characteristic of Microstructures in Bonding Interlayer of Brazed Titanium to Copper (브레이징한 Ti/Cu 접합계면부의 미세조직 특성)

  • 김우열;정병호;이성렬
    • Journal of Welding and Joining
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    • v.13 no.3
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    • pp.106-115
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    • 1995
  • To know the bonding phenomena of Ti/Cu brazed joint, a characteristic of microstructures in bonding interlayer of vacuum brazed pure Ti to Cu has been studied in the temperature range from 1088 to 1133K for various bonding times using Ag-28wt%Cu filler metal. Also intermediate phases formed in bonded interlayer and behavior of layer growth have been investigated. The obtained results in this study are as follows: 1) Liquid insert metal width at the each brazing temperature was proportional to the square root of brazing time, and it was considered that the liquid insert metal width was controlled by the diffusion rate process of primary .alpha.-Cu formed at the Ti side. 2) Intermediate phases formed near the Ti interface were .betha.-Ti and intermetallic compounds TiCu, Ti$_{2}$Cu, Ti$_{3}$Cu, and TiCu. 3) .betha.-Ti formed in Ti base metal durig brazing transformed to lamellar structure, .alpha.-Ti + Ti$_{2}$Cu. The structure came from the eutectoil decomposition reaction in cooling. And the width of .betha.-Ti layer was proportional to the square root of brazing time, and it was considered that the growth of .betha.-Ti layer was controlled by interdiffusion rate process in .betha.-Ti. 4) The layer growth of TiCu, Ti$_{3}$Cu$_{4}$ and TiCu, phases formed near the Ti interface was linerface was linearly proportional to the brazing time, and it was considered that the layer growth of these phases was controlled by the chemical reaction rate at the interface.

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Catalytic Mechanism for Growth of Carbon Nanotubes under CO-H2 Gas Mixture

  • Chung, Uoo-Chang;Kim, Yong-Hwan;Lee, Deok-Bo;Jeong, Yeon-Uk;Chung, Won-Sub;Cho, Young-Rae;Park, Ik-Min
    • Bulletin of the Korean Chemical Society
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    • v.26 no.1
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    • pp.103-106
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    • 2005
  • In order to investigate the catalytic mechanism for the growth of carbon nanotubes (CNTs), a comprehensive study was conducted using carbon materials synthesized at 680 ${^{\circ}C}$ with a gas mixture of CO-H$_2$ after reduction at 800 ${^{\circ}C}$ by H$_2$ gas from iron oxide, and metal Pt. The resulting material was observed by scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD) after a variety of reaction times. The carbon materials synthesized by metal Pt were little affected by reaction time and the sintered particles did not form CNTs. Xray analysis revealed that metal Fe was completely converted to iron carbide (Fe$_3$C) without Fe peaks in the early stage. After 5 min, iron carbide (Fe$_3$C) and carbon (C) phases were observed at the beginning of CNTs growth. It was found that the intensity of the carbon(C) peak gradually increased with the continuous growth of CNTs as reaction time increases. It was also found that the catalyst of growth of CNTs was metal carbide.

Rapid Determination of the Maximum Specific Growth Rates of Nitrogen Oxidizing Bacteria by Fed-Batch Experiments (Fed-Batch 실험장치(實驗裝置)를 이용한 질산화(窒酸化) 미생물(微生物)들의 최대(最大) 성장율(成長率)의 결정(決定)에 관한 실험적(實驗的) 연구(硏究))

  • Lee, Byonghi
    • Journal of Korean Society of Water and Wastewater
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    • v.10 no.3
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    • pp.55-63
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    • 1996
  • Nitrification reaction consists of two reactions: nitritification which oxidizes ammonia nitrogen to nitrite nitrogen and nitratification which oxidizes nitrite nitrogen to nitrate nitrogen. Each reaction is carried out by Nitrosomonas and Nitrobacter, respectively. The effective maximum growth rates for both bacteria have to be determined to design aeration tank whenever the aeration tanks have to nitrify ammonia nitrogen in influent. And these values are very important to use mathematical models such as IAWPRC model to simulate nitrification in activated sludge. There are several methods to determine these valves, however, the Fed-Batch experiments can determine these values within 72 hours. In this study, the mathematical equations and experimental procedures for Fed-Batch test are presented. Also, the experimental data and reported values are compared. The estimated mean values of maximum specific growth rates for Nitrosomonas and Nitrobacter are $0.5010day^{-1}$ and $0.6704day^{-1}$, respectively.

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The growth of zinc oxide particles by coagulation in aerosol reactor (에어로졸 반응기에서 산화아연 입자의 응집 성장)

  • Lee, Jong Ho;Song, Shin Ae;Park, Seung Bin
    • Particle and aerosol research
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    • v.4 no.2
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    • pp.69-75
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    • 2008
  • Nanosize ZnO particles were prepared by oxidation of zinc vapor and the particle growth was modeled by a coagulation model by assuming that the characteristic time for reaction was much shorter than coagulation time and residence time (${\tau}_{reaction}{\ll}{\tau}_{coagulation}{\ll}{\tau}_{residence}$). Experimental measurement of zinc oxide particles diameter was consistent with the predicted result from the coagulation model. For practical purpose of predicting zinc oxide size in areosol reactor, the constant kernel solution is concluded to be sufficient, Uniqueness of nano-scale property of zinc oxide was confirmed by the higher photocatalytic activity of zinc oxide than nanosize titania particles.

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Onset on the Rate Limiting Factors of InP Film Deposition in Horizontal MOCVD Reactor (수평형 MOCVD 반응기 내의 InP 필름성장 제어인자에 대한 영향 평가)

  • Im, Ik-Tae;Sugiyama, Masakazu;Nakano, Yoshiyaki;Shimogaki, Yukihiro
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.73-78
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    • 2003
  • The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

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Numerical Analysis for the Soot Formation Processes in Acetylene-Air Nonpremixed Turbulent Jet Flame (아세틸렌/공기 비예혼합 난류 제트화염의 Soot 생성에 대한 수치해석)

  • 김후중;김용모;윤명원
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.6
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    • pp.80-89
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    • 2002
  • The flame structure and soot formation in Acetylene-Air nonpremixed jet flame are numerically analyzed. We employed two variable approach to investigate the soot formation and oxidation processes. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of pyrene and acetylene. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical model used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reaction flow field.

A Study on Growth Mechanism of Organic Thin Films by the Plasma Polymerization (플라즈마동합법에 의한 유기피막의 성장기정에 관한 연구)

  • 이덕철;한상옥;박구범
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.1
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    • pp.29-35
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    • 1987
  • TPolystyrene thin films are prepared by glow discharge of sytrene monomer vapor th establish the growth mechanism of organic thin films by the plasma polymerization. As the discharge parameters, discharge current(5mA-20mA), frequency (10kHz-50kHz, 13.56MHz), gaspressure (0.2torr-1.5torr), and discharge time(2min-12min)are adopted. Plasma-polymerized filmsof styrene vapor are identified as polystyrene by IR spectra. The thickness of plasma-polymerized films increases with gas pressure, frequency and discharge current in the region of the low frequency and below the allowed gas pressure where the polymerization occurs. It is suggested that the growth mechanism can be explained by ionic reaction in d.c. and low frequency region, and by radical reaction in high frequency region.