• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1460-1462
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• 2001

초고속 전력선 통신을 위한 고주파수 대역에서 안정적인 자기적 특성을 갖는 Ni-Zn ferrite를 개발하기 위해서 투자율은 낮지만 주파수 특성이 우수한 $Ni_{0.8}Zn_{0.2}Fe_2O_4$를 기본조성으로 입자를 성장시키는 $Bi_2O_3$를 0.7, 비저항을 증가 시키는 CaO를 0.3, 그리고 입자를 균일하게 하는 $V_2O_5$를 0.1 wt% 첨가하여 미세구조를 제어하고, 다시 고주파 특성을 향상시킬 것으로 기대되는 $Co_3O_4$를 0, 0.3, 0.5, 0.7 wt%로 변화시켜 자기적 특성을 조사하였다. $Co_3O_4$가 밀도 및 미세구조에는 영향을 미치지 않았으나 0.3, 0.5 wt% 첨가시 첨가하지 않은 조성보다 투자율은 감소하였으나 사용 한계 주파수로 여겨지는 공명주파수가 각각 19.905, 19.205 MHz로 크게 증가하였다. 그리고 전체 전력 손실도 $Co_3O_4$를 첨가했을 때 감소하였으나 첨가량에는 큰 변화가 없었다. 와전류 손실이 전체 전력손실에 지배적인 영향을 미치고 있다.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.730-734
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• 1995

The variation of magnetic permeability and dielectric constant and their relationship with microwave absorbing properties are investigated in sintered Ni-Zn ferrite. Toroid specimens of ${(Ni_{0.5}Zn_{0.5}O)}_{1-y}{(Fe_{2}O_{3})}_{1+y}$ ferrites are prepared by conventional ceramic processing technique. The large change in magnetic permeability is observed by the variation of excess $Fe_{2}O_{3}$ in the Ni-Zn ferrites. The more the iron-excess from y=0.04 to y=0.12, the lower value of both $\mu_{r}'$ and $\mu_{r}"$ is observed. However dielectric permittivity increases with the increase of the increase of the excess $Fe_{2}O_{3}$. The control of permittivity is realized by nitrogen sintering atmosphere and excess $Fe_{2}O_{3}$ respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.519-522
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• 2004

첨가제로 $Bi2O_3$를 첨가하고, 소결 온도를 변화시켜 고주파 내역에서 전자기적 특성이 안정적으로 유지될 수 있는 Ni-Zn 페라이트를 제조하고자 하였다. $Bi2O_3$의 첨가는 액상을 형성하여 소결을 촉진시키며, 0.3 wt% 첨가된 시편에서는 비정상 입자를 성장시켜 높은 전력 손실 특성을 나타내었다. 그러나 $Bi2O_3$의 적정한 첨가는 소결을 촉진시켜 밀도를 증가시키며, 균일한 입자를 형성하여 전력 손실이 감소하였다. Ni-Zn 페라이트에 $Bi2O_3$의 첨가는 공명 주파수 범위의 제어가 가능하며, 소결 촉진 및 밀도의 증가를 가져와 안정적인 재료를 제조할 수 있었다. 투자율의 일정성이 특정 주파수 10MHz 부근에서 급증하면서 급감하는 것은 공명이 생기고, 이러한 현장은 자벽 공명 또는 자벽의 이동에 의해 나타나는 것으로 보여진다.

• Resources Recycling
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• v.12 no.6
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• pp.8-12
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• 2003

According to the recent trend to raise the horizontal scan frequency to increase the image refinement of the High Definition TV and High Resolution Display, material with low core loss is required for the ferrite core for deflection yoke, which is secured even in the high frequency range. liking notice of the influence on the fine structure of Mg-Zn ferrite by the chemical com position and process, low temperature sintering was proceeded. Cu was added to the low loss Mg-Zn system ferrite. After select-ing MgO, ZnO, $Fe_2$$O_3$, CuO, MgO was substituted for CuO while varying the composition ratio. Then the sample was sintered for 3 hours between $980～1350^{\circ}C$ Magnetic permeability, power consumption, shrinkage rate, core loss were measured. The start-ing temperature to test the shrinkage of the sample was nearby $900^{\circ}C$, it increased according to the substitution process of Cu, and the firing temperature was lowered about $-50～-75^{\circ}C$ alongside of the process.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1002-1004
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• 2009

Solution-processed indium-gallium-zinc-oxide thin-film transistors were fabricated by sol-gel method. By a combinatorial study of InGaZnO multi-component system, optimum molar ratio of In, Ga, and Zn has been selected. By adjusting the In:Ga:Zn molar ratio, TFTs with field-effect mobility of 0.5 ~ 1.5 $cm^2$/V-s, threshold voltage of -5 ~ 5 V, and subthreshold slope of 1.5 ~ 2.5 V/decade were achieved.

• Progress in Superconductivity
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• v.11 no.1
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• pp.47-51
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density ($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers in $YBa_2Cu_3O_{7-{\delta}}$ films for enhancement of their $J_c$. We studied the microstructures and characteristic of $YBa_2Cu_3O_{7-{\delta}}$ films fabricated on $SrTiO_3$ (100) substrates with ZnO nanorods as pinning centers. Au catalyst nanoparticles were synthesized on STO substrates with self assembled monolayer to control the number of ZnO nanorods. The density of Au nanoparticles is approximately $240{\sim}260{\mu}m^{-2}$ with diameters of $41{\sim}49nm$. ZnO nanorods were grown on STO by hot-walled PLD with Au nanoparticles. Typical size of ZnO nanorod was around 179 nm in diameter and $2{\sim}6{\mu}m$ in length respectively. YBCO films deposited directly on STO substrates show the c-axis orientation, while YBCO films with ZnO nanorods exhibit any mixed phases without any typical crystal orientation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.688-688
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• 2013

Al-doped ZnO (AZO) thin films have attracted a lot of attention as a cheap transparent conducting oxide (TCO) material that can replace the expensive Sn-doped In2O3. In particular, AZO thin films are widely used as a window layer of chalcogenide-based thin film solar cells such as Cu(In,Ga)Se2 and Cu2ZnSnS4 (CZTS). Mostly important requirements for the window layer material of the thin film solar cells are the high transparency and the low sheet resistance, because they influence the light absorption by the activelayer and the electron collection from the active layer, respectively. In this study, we prepared the AZO thin films by RF magnetron sputtering using a ZnO/Al2O3 (98：2wt%) ceramic target, and the effect of the sputtering condition such as the working pressure, RF power, and the working distance on the optical, electrical, and crystallographic properties of the AZO thin films was investigated. The AZO thin films with optimized properties were used as a window layer of CZTS thin film solar cells. The CZTS active layers were prepared by the electrochemical deposition and the subsequent sulfurization process, which is also one of the cost-effective synthetic approaches. In addition, the solar cell properties of the CZTS thin film solar cells, such as the photocurrent density-voltage (J-V) characteristics and the external quantum efficiency (EQE) were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.431-431
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• 2016

Typical Cu(In,Ga)Se2 (CIGS)-based solar cells have a buffer layer between CIGS absorber layer and transparent ZnO front electrode, which plays an important role in improving the cell performance. Among various buffer materials, chemical bath deposition (CBD)-ZnS is being steadily studied to alternative to conventional CdS and the efficiency of CBD-ZnS/CIGS solar cell shows the comparable values with that of CdS/CIGS solar cell. The intriguing thing is that reversible changes occur after exposure to illumination due to the metastable defect states in completed ZnS/CIGS solar cell, which induces an improvement of solar cell performance. Thus, it implies that the understanding of metastable defects in CBD-ZnS/CIGS solar cell is important issue. In this study, we fabricate the ITO/i-ZnO/CBD-ZnS/CIGS/Mo/SLG solar cells by controlling the NH4OH mole concentration (from 2 M to 3.5 M) of CBD-ZnS buffer layer and observe their conversion efficiency with and without light soaking for 1 hr. From the results, NH4OH mole concentration and light exposure can significantly affect the CBD-ZnS/CIGS solar cell performance. In order to investigate that which layer can contain metastable defect states to influence on solar cell performance, impedance spectroscopy and capacitance profiling technique with exposure to illumination have been applied to CBD-ZnS/CIGS solar cell. These techniques give a very useful information on the density of states within the bandgap of CIGS, free carriers density, and light-induced metastable effects. Here, we present the rearranged charge distribution after exposure to illumination and suggest the origin of the metastable defect states in CBD-ZnS/CIGS solar cell.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.37-37
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• 2008

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.152-156
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• 2016

Experimental research on the preparation of photocatalyst for the decomposition of brilliant blue FCF ($C_{37}H_{31}O_9N_2S_3Na_2$) was performed. $TiO_2$ and ZnO powders were prepared from titanium (IV) sulfate and zinc acetate at low reaction temperature and atmospheric pressure by hydrothermal precipitation method without calcination. In addition, $TiO_2$ was prepared with cationic surfactant CTAB (Hexadecyltrimethyl ammonium bromide) at the same conditions. The physical properties of prepared $TiO_2$ and ZnO, such as crystallinity, average particle size and absorbance, were investigated by XRD, Zeta-potential meter and DRS. And, the photocatalytic degradation of brilliant blue FCF has been studied in the batch reactor under UV radiation. For the photocatalysts prepared without CTAB, $TiO_2$ has smaller particle size and larger absorbance and photocatalytic reaction rate than ZnO. And $TiO_2$, prepared with CTAB whose concentration is 1/10 of that of precursor, shows 15% higher than that prepared without CTAB in final photocatalytic degradation ratio of brilliant blue FCF.