• Title/Summary/Keyword: J-E properties

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The microstructure and conduction mechanism of the nonlinear ZnO varistor with $Al_2O_3$ additions ($Al_2O_3$가 미량 첨가된 비선형성 ZnO 바리스터의 미세구조와 전도기구)

  • 한세원;강형부;김형식
    • Electrical & Electronic Materials
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    • v.9 no.7
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    • pp.708-718
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    • 1996

  • The microstructure and electrical properties of the nonlinear ZnO varistor with A1$_{2}$ $O_{3}$ additions is investigated. The variation of nonlinear behavior with A1$_{2}$ $O_{3}$ additions is indicated from J-E and C-V measurement to be a result of the change of the interface defects density $N_{t}$ at the grain boundaries and the donor concentration $N_{d}$ in the ZnO grains. The optimum composition which has the nonlinear coefficients of -57 was observed in the sample with 0.005wt% A1$_{2}$ $O_{3}$ additions. The conduction mechanism at the pre-breakdown region is consistent with a Schottky thermal emission process obeying a relation given by $J^{\var}$exp[-(.psi.-.betha. $E^{1}$2/)kT] and the conduction process at the breakdown region follows a Fowler-Nordheim tunneling mechanism of the form $J^{\var}$exp(-.gamma./E).

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Superconducting properties and microstructure of electron beam irradiated MgB2 superconductors

  • Kim, C.J.;Lee, Y.J.;Cho, I.H.;Jun, B.H.
    • Progress in Superconductivity and Cryogenics
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    • v.24 no.1
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    • pp.18-22
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    • 2022

  • The effect of electron beam (EB) irradiation on superconducting properties and microstructures of MgB2 bulk superconductors were investigated. At E-beam doses of 1×1016 e/cm2 and 1×1017 e/cm2, the effect of irradiation on a superconducting transition temperature (Tc) of MgB2 was weak. As a dose increases to 5×1017 e/cm2, Tc decreases by 0.5 K. The critical current density (Jc) measured at 4.2 K and 20 K, and 0 T - 5 T increases slightly as exposure time increases. X-ray diffraction for the irradiation surface of MgB2 shows that the diffraction intensity of (hkl) peaks decreases proportionally as the exposure time increases. This indicates that the crystallinity of MgB2 was degraded by irradiation. TEM investigation for the irradiated sample showed distorted lattice structure, which is consistent with the XRD results. The Jc increase and Tc reduction of MgB2 by irradiation are believed to be caused by the lattice distortion.

  • https://doi.org/10.9714/psac.2022.24.1.018 인용 PDF KSCI

The structural, optical and photocatalytic properties of $TiO_2$ thin films fabricated by do magnetron sputtering (직류 마그네트론 스퍼터링법으로 제조된 $TiO_2$ 박막의 구조적, 광학적 특성 및 광촉매 효과)

  • Lim, J.M.;Yang, H.H.;Kim, Y.J.;Park, J.Y.;Jeong, W.J.;Park, G.C.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07a
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    • pp.420-423
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    • 2003

  • [ $TiO_2$ ] thin films were fabricated by DC magnetron sputtering system at by controlling deposition times, ratios of $Ar:O_2$ partial presser ratio and substrate conditions. And the surface, cross-section morphology, microstructure, and composition ratio of the films were analyzed by FE-SEM, TEM and XPS. Besides, the optical absorption and transmittance of the $TiO_2$ films were measured by a UV-VIS-NIR Spectrophotometer, and photocatalytic properties were studied by G C Analyzer & Data Analysis system. As the result, when $TiO_2$ thin film was made at deposition time of 120[min] and $Ar:O_2$ ratio of 60:40, the best structural and optical properties among many thin films could be accepted. The best results of properties were as follows: thickness; $360{\sim}370[nm]$, grain size; 40[m], gap between two peak binding energy, $5.8{\pm}0.05[eV]$ ($2p_{3/2}$ peak and $2p_{1/2}$ peak of Ti was show at $458.3{\pm}0.05[eV]$ and $464.1{\pm}0.05[eV]$ respectively), binding energy; $530{\pm}0.05\;[eV]$, opticalenergy band gap; 3.4[eV].

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Electronic and Optical Properties of amorphous and crystalline Tantalum Oxide Thin Films on Si (100)

  • Kim, K.R.;Tahir, D.;Seul, Son-Lee;Choi, E.H.;Oh, S.K.;Kang, H.J.;Yang, D.S.;Heo, S.;Park, J.C.;Chung, J.G.;Lee, J.C.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.382-382
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    • 2010

  • $TaO_2$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility in achieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFETchannel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. The atomic structure of amorphous and crystalline Tantalum oxide ($TaO_2$) gate dielectrics thin film on Si (100) were grown by utilizing atomic layer deposition method was examined using Ta-K edge x-ray absorption spectroscopy. By using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) the electronic and optical properties was obtained. In this study, the band gap (3.400.1 eV) and the optical properties of $TaO_2$ thin films were obtained from the experimental inelastic scattering cross section of reflection electron energy loss spectroscopy (REELS) spectra. EXAFS spectra show that the ordered bonding of Ta-Ta for c-$TaO_2$ which is not for c-$TaO_2$ thin film. The optical properties' e.g., index refractive (n), extinction coefficient (k) and dielectric function ($\varepsilon$) were obtained from REELS spectra by using QUEELS-$\varepsilon$(k, $\omega$)-REELS software shows good agreement with other results. The energy-dependent behaviors of reflection, absorption or transparency in $TaO_2$ thin films also have been determined from the optical properties.

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Predicting Mechanical Response of Multilayered Aluminum Sheet Using Finite Element Analysis (유한요소해석 연계 알루미늄 다층판재의 기계적 거동 예측)

  • Sung, J.Y.;Kim, M.H.;Bong, H.J.;Lee, K.S.;Kim, M.J.;Kim, J.H.
    • Transactions of Materials Processing
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    • v.29 no.6
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    • pp.347-355
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    • 2020

  • The mechanical responses of multilayered aluminum sheet fabricated by roll bonding, i.e., A1050/A3004 (65% A1050, 35% A3004 by thickness), were investigated via combined experiment and finite element (FE) analysis. The mechanical properties were measured using uniaxial tensile tests in various loading directions for the multilayered sheet. The corresponding tests for individual layers were also conducted. The testing samples were prepared by wire electro discharge machining (EDM). Stress-strain curves and Lankford coefficients of the multilayered sheet were then predicted by FE simulations. The measured mechanical properties of the individual layers were utilized as inputs for the simulation. Two yield functions, i.e., isotropic von-Mises and anisotropic non-quadratic Hill1948, were employed. Predicted results were compared with the experimental data and further discussed.

  • https://doi.org/10.5228/KSTP.2020.29.6.347 인용 PDF KSCI HTML

Synthesis and Electroluminescent Properties of Cabazolyl Vinylene Derivatives

  • Seo, H.J.;Park, H.C.;Lee, S.E.;Park, J.W.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.952-954
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    • 2003

  • We report the photo-(PL) and electroluminescence (EL) properties of new conjugated compounds based on carbazolyl vinylene moiety, 3,3'-(1,4-phenylene di-2,1-ethenediyl) bis[9-ethyl-(E,E)-9H-carbazole](PEEC) and 3,3'-([1,1'-biphenyl]-4,4'-diyldi-2,1-ethenediyl)bis[9-ethyl-9H-carbazole](BPEEC), as emitting materials. The ITO/m-MTDATA/NPB/BPEEC/Alq3/LiF/Al device shows bluish-green EL spectrum at 490nm and turn-on voltage at 8V. PEEC shows bluish-green EL around ${\lambda}$ max=496nm and turn-on voltage at 6V and 2.4 Cd/A efficiency in ITO/m-MTDATA/NPB/PEEC/Alq3/LiF/Al device.

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