• Title/Summary/Keyword: $O_2$ partial pressure

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Integration of Ba0.5Sr0.5TiO3Epitaxial Thin Films on Si Substrates and their Dielectric Properties (Si기판 위에 Ba0.5Sr0.5TiO3 산화물 에피 박막의 집적화 및 박막의 유전 특성에 관한 연구)

  • Kim, Eun-Mi;Moon, Jong-Ha;Lee, Won-Jae;Kim, Jin-Hyeok
    • Journal of the Korean Ceramic Society
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    • v.43 no.6 s.289
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    • pp.362-368
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    • 2006
  • Epitaxial $Ba_{0.5}Sr_{0.5}TiO_3$ (BSTO) thin films have been grown on TiN buffered Si (001) substrates by Pulsed Laser Deposition (PLD) method and the effects of substrate temperature and oxygen partial pressure during the deposition on their dielectric properties and crystallinity were investigated. The crystal orientation, epitaxy nature, and microstructure of oxide thin films were investigated using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Thin films were prepared with laser fluence of $4.2\;J/cm^2\;and\;3\;J/cm^2$, repetition rate of 8 Hz and 10 Hz, substrate temperatures of $700^{\circ}C$ and ranging from $350^{\circ}C\;to\;700^{\circ}C$ for TiN and oxide respectively. BSTO thin-films were grown on TiN-buffered Si substrates at various oxygen partial pressure ranging from $1{\times}10^{-4}$ torr to $1{\times}10^{-5}$ torr. The TiN buffer layer and BSTO thin films were grown with cube-on-cube epitaxial orientation relationship of $[110](001)_{BSTO}{\parallel}[110](001)_{TiN}{\parallel}[110](001)_{Si}$. The crystallinity of BSTO thin films was improved with increasing substrate temperature. C-axis lattice parameters of BSTO thin films, calculated from XRD ${\theta}-2{\theta}$ scans, decreased from 0.408 m to 0.404 nm and the dielectric constants of BSTO epitaxial thin films increased from 440 to 938 with increasing processing oxygen partial pressure.

A Study of the Semiconductivity of Polycrystalline Cuprous Oxide (다결정 산화구리의 반도성에 관한 연구)

  • Choi, Jae-Shi;Yo, Chul-Hyun
    • Journal of the Korean Chemical Society
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    • v.16 no.2
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    • pp.74-79
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    • 1972
  • The semiconductivity of polycrystalline $Cu_2O$ has been studied between $220^{\circ}C$ and $680^{\circ}C under partial pressures of oxygen from $4.06{\times}10^{-3}\;to\;10^{-5 }\;mmHg$. The plots of log conductivity vs 1/T at constant oxygen pressure were found to be linear, and the activation energies obtained from the slopes of these plots above the first transition point showed that the energies were greater under high oxygen pressure than under low pressure. The transition points between the stable range and the unstable range of $Cu_2O$ were found from the curves. The dependence of the semiconductivity on the $O_2$ pressure, in the above temperature range, is shown hysteresis.

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Copper Solubility in Al2O3-CaO-SiO2-MgO Slag (Al2O3-CaO-SiO2-MgO계 슬래그 중 Cu의 용해도)

  • Han, Bo-Ram;Kim, Eung-Jin;Sohn, Ho-Sang
    • Resources Recycling
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    • v.23 no.1
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    • pp.33-39
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    • 2014
  • In this study, the solubility of Cu, which is a main metal component of wasted PCB, in $CaO-SiO_2-Al_2O_3-MgO$ slag system was investigated. Each 20 grams of Cu chips and the quaternary slag manufactured was placed in an carbon crucible and melted for 10 hours in the temperature between 1673 K and 1825 K to confirm the equilibrium state. The oxygen partial pressure was controlled by the ratio of CO and Ar gas in the range of $10^{-17.23}$ to $10^{-15.83}$ atm. The concentration of Cu in the slag increased with increasing oxygen partial pressure, slag basicity, and MgO content in the slag. The concentration of Cu in the slag decreased with increasing temperature. The Cu dissolution reaction in the slag is an exothermic reaction.

A Study of Hydrodenitrogenation of Quinoline Catalyzed by Sulfided $Ni-Mo/\gamma - Al_2O_3$ (황화 $Ni-Mo/\gamma - Al_2O_3$ 촉매상에서 Quinoline의 수소첨가탈질반응에 관한 연구)

  • 최응수;이원묵;김경림
    • Journal of Korean Society for Atmospheric Environment
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    • v.5 no.1
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    • pp.52-61
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    • 1989
  • The hydrodenitrogenation of quinoline dissolved in n-heptane was studied over sulfided Ni-Mo/$\gamma-Al_2O_3$ catalyst at the range of the temperature between 553 K and 673 and the total pressure between $20 \times 10^5$ Pa and $60 \times 10^5$ Pa in a fixed bed flow reactor. Quinoline conversion was very high at relatively low temperature and total pressure, and decreased with quinoline partial pressure. The thermodynamic equilibrium between quinoline and Py-THQ existed in wide ranges of experimental conditions and shifted in favor of quinoline at higher temperature. At the range of the temperature betwwen 553 K and 673 K and at the total pressure $60 \times 10^5$ Pa, the quinoline reaction rate was 1st order with respect to the concentr4ation of quinoline and its apparent activation energy was 7.15 Kcal/mole.

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Influence of the Water Vapor Content on the Hydrogen Reduction Process of Nanocrystalline NiO

  • Jung, Sung-Soo;An, Hyo-Sang;Lee, Jai-Sung
    • Korean Journal of Metals and Materials
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    • v.48 no.4
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    • pp.315-319
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    • 2010
  • In this study, the hydrogen reduction behavior of ball-milled NiO nanopowder was investigated depending on the partial pressure of water vapor. The hydrogen reduction behavior was analyzed by thermogravimetry and hygrometry under heating to 873 K in hydrogen. In order to change the partial pressure of the water vapor, the dew point of hydrogen was controlled in the range of 248 K~293 K by passing high-purity hydrogen through a saturator that contained water. Interestingly, with the increase in the dew point of the hydrogen atmosphere, the first step of the hydrogen reduction process decreased and the second step gradually increased. After the first step, a pore volume analysis revealed that the pore size distribution in the condition with a higher water vapor pressure shifted to a larger size, whereas the opposite appearedat a lower pressure. Thus, it was found that the decrease in the pore volume during the chemical reaction controlled process at a dew point of 248 K caused a reduction in retardation in the diffusion controlled process.

Coulometric Titration for the Determination of Nonstoichiometry in Ni1-XO (전하량적정법에 의한 Ni1-XO의 Nonstoichiometry 측정)

  • Suh, Sang-hyuk;Oh, Seung-Mo
    • Applied Chemistry for Engineering
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    • v.2 no.4
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    • pp.385-392
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    • 1991
  • Nonstoichiometry and defect model for $Ni_{1-x}O$ were determined by coulometric titration method. In the temperature range of 1123-1198K and oxygen partial pressure of 0.21-0.1 atm, the nonstoichiometry was found to be proportional to the fourth root of the oxygen partial pressure. This pressure dependence can be explained by the fact that nonstoichiometric $Ni_{1-x}O$ contains singly ionized metal vacancies as the predominant point defects. At T=1173K and $Po_2=0.21atm$, the nonstoichiometry, x was $1.21{\times}10^{-4}$. The standard formation enthalpy of defects in $Ni_{1-x}O$ was found, on the basis of this defect model, to be 0.95 eV. Also the result indicates that both of singly and doubly ionized metal vacancies are simultaneously present at above 1248K.

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Soft Magnetic Properties of CoFeAlO Thin Films for Ultrahigh Frequency Applications (고주파용 CoFeAlO계 박막의 자기적 특성)

  • Kim, Hyeon-Bin;Yun, Dae-Sik;Ha, N.-D.;Kim, Jong-O
    • Journal of the Korean Magnetics Society
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    • v.15 no.1
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    • pp.17-20
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    • 2005
  • The influence of $O_2$ partial pressure on saturation mgnetization, coercivity, anisotropy field and effective permeability (over 1GHz) of as-deposited Co-Fe-Al-O thin films, which were fabricated by RF magnetron reactive sputtering method, were investigated. The $Co_{69.9}Fe_{20.5}A_{14.4O_{5.2}$ thin film fabricated at $O_2$ partial pressure of 4% exhibits the best magnetic softness with saturation magnetization 4${$pi}$Ms of 18.1 kG, coercivity of 0.82 Oe, anisotropy field ($H_k$) of Oe, and effective permeability (${\mu}_{eff}$) about 1,024 above 1 GHz. the electrical resistivity of Co-Fe-Al-O thin films were increased with increasing $O_2$ partial pressure, the electrical resistivity of $Co_{69.9}Fe_{20.5}A_{14.4O_{5.2}$ thin film with the best soft magnetic properties was 560.7 ${\mu}{\Omega}$am. Therefore, It is assumed that the good soft magnetic properties of $Co_{69.9}Fe_{20.5}A_{14.4O_{5.2}$ thin film results from high electrical resistivity and large anisotropy field.

Direct Bonding of Cu/AlN using Cu-Cu2O Eutectic Liquid (Cu-Cu2O계 공융액상을 활용한 Cu/AlN 직접접합)

  • Hong, Junsung;Lee, Jung-Hoon;Oh, You-Na;Cho, Kwang-Jun;Riu, Doh-Hyung;Oh, Sung-Tag;Hyun, Chang-Yong
    • Journal of Powder Materials
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    • v.20 no.2
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    • pp.114-119
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    • 2013
  • In the DBC (direct bonding of copper) process the oxygen partial pressure surrounding the AlN/Cu bonding pairs has been controlled by Ar gas mixed with oxygen. However, the direct bonding of Cu with sound interface and good adhesion strength is complicated process due to the difficulty in the exact control of oxygen partial pressure by using Ar gas. In this study, we have utilized the in-situ equilibrium established during the reaction of $2CuO{\rightarrow}Cu_2O$ + 1/2 $O_2$ by placing powder bed of CuO or $Cu_2O$ around the Cu/AlN bonding pair at $1065{\sim}1085^{\circ}C$. The adhesion strength was relatively better in case of using CuO powder than when $Cu_2O$ powder was used. Microstructural analysis by optical microscopy and XRD revealed that the interface of bonding pair was composed of $Cu_2O$, Cu and small amount of CuO phase. Thus, it is explained that the good adhesion between Cu and AlN is attributed to the wetting of eutectic liquid formed by reaction of Cu and $Cu_2O$.

Humidity-Sensing Properties of RF Sputtered Vanadium Oxide Thin Films (RF 스퍼터된 바나듐 산화막의 습도 감지 특성)

  • Choi, Bok-Gil;Choi, Chang-Kyu;Kim, Sung-Jin
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.10
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    • pp.475-480
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    • 2006
  • Vanadium oxide thin films (VOx) have been deposited by RF magnetron sputtering from $V_2O_5$ target under different oxygen partial pressure ratios(0%, 10%) and substrate temperatures$(27^{\circ}C,\;400^{\circ}C)$. Crystallographic structure and morphology of the films are studied by XRD and SEM. Humidity-sensing properties of resistive sensors having interdigitated electrode structure are characterized through electrical conduction measurements. The films deposited at room temperature are amorphous whereas the ones deposited above foot are polycrystalline. The sensors show good response to humidity over 20%RH to 80%RH. Vanadium oxide thin films deposited with $0%O_2$ partial pressure at $400^{\circ}C$ exhibit greater sensitivity to humidity change than others.