• Title/Summary/Keyword: Acceptor

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Evaluation of Acceptor Binding Energy of Nitrogen-Doped Zinc Oxide Thin Films Grown by Dielectric Barrier Discharge in Pulsed Laser Deposition

  • Lee, Deuk-Hee;Chun, Yoon-Soo;Lee, Sang-Yeol;Kim, Sang-Sig
    • Transactions on Electrical and Electronic Materials
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    • v.12 no.5
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    • pp.200-203
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    • 2011
  • In this research, nitrogen (N)-doped zinc oxide (ZnO) thin films have been grown on a sapphire substrate by dielectric barrier discharge (DBD) in pulsed laser deposition (PLD). DBD has been used as an effective way for massive in-situ generation of N-plasma under conventional PLD process conditions. Low-temperature photoluminescence spectra of N-doped ZnO thin films provided near-band-edge emission after a thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound excitation peak ($A^{\circ}X$) that indicated acceptor doping of ZnO with N. The acceptor binding energy of the N acceptor was estimated to be approximately 145 MeV based on the results of temperature-dependent photoluminescence (PL) measurements.

The critical Mg doping on the blue light emission in p-type GaN thin films grown by metal-organic chemical vapor deposition

  • Kim, Keun-Joo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.09a
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    • pp.52-59
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    • 2001
  • The photoluminescence and the photo-current from p-type GaN films were investigated on both room- and low-temperatures for various Mg doping concentrations. At a low Mg doping level, there exists a photoluminescence center of the donor and the acceptor pair transition of the 3.28-eV band. This center is correlated with the defects for a shallow donor of the VGa and for an acceptor of MgGa. The acceptor level shows the binding energy of 0.2-0.25 eV, which was observed by the photon energy of the photo-current signal of 3.02-3.31 eV. At a high Mg doping level, there is a photoluminescence center of a deep donor and an acceptor pair transition of the 2.76-eV blue band. This center is attributed to the defect structures of MgGa-VN for the deep donor and MgGa for the acceptor. For low. doped samples, thermal annealing provides an additional photo-current signal for an unoccupied deep acceptor levels of 0.87-1.35 eV above valence band, indicating the p-type activation.

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Research Method of Fatty Acids Transfer between Phospholipid Model Membranes (인지질 모델막에서의 지방산 이동에 관한 연구 방법)

  • 임병순;김혜경;김을상
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.26 no.4
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    • pp.743-750
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    • 1997
  • Direct measurement of the kinetics of free fatty acid transfer between phospholipid model membrane is technically limited by the rapid nature of the transfer process. Separation of membrane-bound fatty acid by centrifugation has shown that although the equilibrium distribution of free fatty acid is determined by this method, fatty acid transfer occurs too rapidly for accurate kinetic measurements. Recently fluorescence resonance energy transfer(FRET) assay has been developed to examine transfer of fatty acids between membranes. Donor membranes which has fluorescent fatty acid, anthroyloxy fatty acid(AOFA), is mixed with acceptor membranes which has non-interchangeable fluorescent quencher, nitrobenzo-xadiazol(NBD), using stopped flow apparatus. As the fluorescent fatty acids transfer from donor membrane to acceptor membrane, fluorescence intensity would be decreased and the rate and degree of fatty acid transfer can be analyzed. Fatty acid transfer between micelles is more complicated because of bile salt. Therefore in experiments with micelles, fluorescence self quenching assay is used. At high concentrations, a fluorophore tends to quench its own fluorescence causing a reduction in fluorescence intensity. Donor micelles contained self quenching concentrations of fluorophore and acceptor micelles had no fluorophore. Upon mixing of donor and acceptor micelles, the rate of transfer of the fluorophore from the donor to the acceptor was measured by monitoring the release in self quenching when its concentration in donor decreased over time.

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Acceptor reaction of a novel transfructosylating enzyme from Bacillus sp.

  • Kim, Yeong-Mi;Sinha, Jayanta;Park, Jong-Pil;Yun, Jong-Won
    • 한국생물공학회:학술대회논문집
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    • 2000.11a
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    • pp.583-586
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    • 2000
  • Many different oligosaccharides were produced by transferring the fructose residue of sucrose to maltose, cellobiose, lactose and sucrose (self-transfer), where their yields of fructosylated acceptor products accounted for $26{\sim}30%$ (w/w). The maximum conversion yield (30%) was obtained in fructosyl cellobioside formation with 500 g sucrose/l (substrate) and 200 g cellobiose/l (acceptor). These four acceptors gave various products having DP (degree of polymerization) $2{\sim}7$ by successive transfer reactions.

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Acarbose Effect for Dexran Synthesis, Acceptor and Disproportionation Reactions of Leuconostoc mesenteroides B-512FMCM Dextransucrase

  • Kim, Do-Man;Park, Kwan-Hwa;Robyt, John F.
    • Journal of Microbiology and Biotechnology
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    • v.8 no.3
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    • pp.287-290
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    • 1998
  • Acarbose effectively inhibited the synthesis of dextran, and the inhibition pattern was a noncompetitive type with a $K_i$ value of 1.35 mM. It also inhibited the disproportionation reaction of dextransucrase with isomaltotriose and decreased the efficiency of the maltose acceptor reaction. Increased concentration of dextransucrase or maltose in reaction digests, however, decreased the degree of inhibition by acarbose.

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A Study on Shock Transmission of Pyrotechnic Initiator (격벽착화기 내 충격 전달에 관한 연구)

  • Kim, Bohoon;Kim, Minsung;Yoh, Jai-ick
    • 한국연소학회:학술대회논문집
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    • 2015.12a
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    • pp.223-226
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    • 2015
  • A pyrotechnic system that consists of donor/acceptor pair separated by a gap relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor charges. We apply a level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized RDX as acceptor charge. The complex shock interaction, critical gap thickness, acoustic impedance, and go/no-go characteristics of the pyrotechnic system are quantitatively investigated.

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Li-doped p-type ZnS Grown by Molecular Beam Epitaxy

  • Lee Sang-Tae
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.3
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    • pp.313-318
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    • 2005
  • Li-doped ZnS layers were grown by molecular beam epitaxy. It was found that relatively low growth temperature is suitable for effective incorporation of Li acceptors. The layers grown under optimized conditions exhibited photoluminescence spectra dominated by neutral-acceptor-bound excitons. Such layers also showed electrically p-type behavior in capacitance-voltage characteristics. The net acceptor concentration is estimated to be approximately $3{\times}10^{15}\;cm^{-3}$.

Defect Chemistry of BaTiO_3$ Codoped with Mn and Nb

  • Han, Young-Ho;Shin, Dong-Jin
    • The Korean Journal of Ceramics
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    • v.4 no.2
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    • pp.68-71
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    • 1998
  • The effect of Mn and Nb additions on the electrical properties of BaTiO$_3$ has been studied by means of equilibrium electrical conductivity as a function of temperature, oxygen partial pressure(Po$_2$) and composition. If the manganese ion is added to the normal Ti site, i.e. BaTi$_{1-x}Mn_xO_{\delta-6}$, the equilibrium conductivity shows strong evidence of acceptor-doped behavior. The conductivity minimum, corresponding to the transition from oxygen excess, p-type behavior to oxygen deficient, n-type behavior with decreasing Po$_2$, is displaced to lower Po$_2$ and is broadened and flattened. The partial replacement of Mn ion with Nb decreases the acceptor-doped effect and the total replacement exhibits a typical donor-doped behavior. It was confirmed that unlike undoped or other acceptor-doped behavior. It was confirmed that unlike undoped or other acceptor-doped samples, for the p-type region, the electrical conductivity follows the 1/6th power dependence of oxygen partial pressure.

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Effect of Electron Acceptor on Anaerobic Toluene Biodegradation in Rice Field and Tidal Mud Flat (논과 갯벌에서 톨루엔의 혐기성 생분해에 미치는 전자수용체의 영향)

  • 조경숙
    • Microbiology and Biotechnology Letters
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    • v.31 no.2
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    • pp.197-200
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    • 2003
  • In oil-contaminated environments, anaerobic biodegradation of toluene depended on the concentration and distribution of terminal electron acceptor as well as the physicochemical properties such as DO concentration, redox potential and pH. This study showed the anaerobic biodegradation of toluene in two different soils by using nitrate reduction, ferric iron reduction, sulfate reduction and methanogensis. Toluene degradation rates in the soil samples taken from rice filed and tidal mud flat by nitrate reduction were higher than those by other processes. Tho soil samples from the two fields were enriched for 130 days by providing toluene as a sole carbon source and nitrate or sulfate as a terminal electron acceptor. The toluene degradation rates in the enriched denitrifying consortia obtained from the rice field and tidal mud flat soil were 310.7 and 200.6 $\mu$mol$ L^{-1}$ / $d^{-1}$, respectively. The toluene (legradation rates in the enriched sulfate-reducing consortia from the fields ranged fi-om 149.1 to 86.1$\mu$mol $L^{-1}$ / $d^{-1}$ .

Growth and characterization of CdTe single crystal by vertical Bridgman method (수직 Bridgman 법에 의한 CdTe 단결정 성장과 특성)

  • Hong, Myung-Seok;Hong, Kwang-Joon
    • Journal of Sensor Science and Technology
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    • v.14 no.6
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    • pp.369-373
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    • 2005
  • High quality CdTe single crystal for the solar cell fabrication was grown by vertical Bridgman method. The etch pits patterns of (111) surfaces of CdTe etched by Nakagawa solution was observed the (111)A compesed of Cd atoms with typical triangle etch pits of pyramid mode. From the photoluminescence measurement on (111)A, we observed free exciton ($E_{x}$) existing only high quality crystal and neutal acceptor bound exciton ($A^{0}$,X) having very strong peak intensity. Then, the full width at half maximum and binding energy of neutral acceptor bound exciton were 7 meV and 5.9 meV, respectively. By Haynes rule, an activation enery of impurity was 59 meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.