• Korean Journal of Materials Research
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• v.7 no.10
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• pp.871-871
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• 1997

(1-x)CaTiO/sub 3/-xLa(Zn/sub 1/2/Ti/sub 1/2/)O/sub 3/의 마이크로 유전특성을 조사하였다. x가 증가함에 따라 비유전율과 공진주파수의 온도계수는 감소하였으며, Qㆍf/sub 0/는 증가하였다. 그 결과 x=0.5인 (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/)O/sub 3/의 조성에서 ε/sub r/=51, Qㆍf/sub 0/=38,000 (at 7 GHz), τ/sub f/=+5ppm/℃의 유전특성이 나타났다. (Ca/sub 0.5/La/sub 0.5/)(Ti/sub 0.75/Zn/sub 0.25/) O/sub 3/조성의 소결온도를 저하시키기 위하여 Bi/sub 2/O/sub 3/를 주조성으로한 소결체를 첨가하여 소결 및 유전특성을 조사하였다. 1wt% 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 150℃ 낮아졌으며, 비유전율 (ε/sub r/), 공진주파수의 온도계수(τ/sub f), Qㆍf/sub 0/가 각각 50+5ppm/℃, 35,000인 마이크로파 유전특성이 얻어졌다. 또한 3wt%의 0.76Bi/sub 2/O/sub 3/-0.24NiO가 첨가된 경우 소결온도는 200℃ 저하되었고, 비유전율 (ε/sub r/)과 공진주파수의 온도계수 (τ/sub f)는 변하기 않았으나, Qㆍf/sub 0/값이 38,000에서 25,000으로 저하되었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.293-297
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• 2010

We have studied the optical and electrical properties of a-IGZO thin films on the n-type semiconductor fabricated by RF magnetron sputtering method. The ceramic target was used in which $In_2O_3$, $Ga_2O_3$ and ZnO powder were mixed with 1:1:2 mol% ratio and furnished. The RF power was set at 25 W, 50 W, 75 W and 100 W as a variable process condition. The transmittance of the films in the visible range was above 80%, and it was 92% in the case of 25 W power. AFM analysis showed that the roughness increased as increasing RF power, and XRD showed amorphous structure of the films without any peak. The films are electrically characterized by high mobility above 10 $cm^2/V{\cdot}s$ at low RF power, high carrier concentration and low resistivity. It is required to study further finding the optimal process condition such as lowering the RF power, prolonging the deposition ratio and qualification analysis.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.50.1-50.1
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• 2009

Transparent conductive oxides (TCOs) play an important role in thin-film solar cells in terms of low cost and performance improvement. Al-doped ZnO (AZO) is a very promising material for thin-film solar cellfabrication because of the wide availability of its constituent raw materials and its low cost. In this study, AZO films were prepared by low pressurechemical vapor deposition (LPCVD) using trimethylaluminum (TMA), diethylzinc(DEZ), and water vapor. In order to improve the absorbance of light, atypical surface texturing method is wet etching of front electrode using chemical solution. Alternatively, LPCVD can create a rough surface during deposition. This "self-texturing" is a very useful technique, which can eliminate additional chemical texturing process. The introduction of a TMA doping source has a strong influence on resistivity and the diffusion of light in a wide wavelength range.The haze factor of AZO up to a value of 43 % at 600 nm was achieved without an additional surface texturing process by simple TMA doping. The use of AZO TCO resulted in energy conversion efficiencies of 7.7 % when it was applied to thep-i-n a-Si:H thin film solar cell, which was comparable to commercially available fluorine doped tin oxide ($SnO_2$:F).

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2387-2392
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• 2009

A composite film of multi-walled carbon nanotube (MWCNT)/sol-gel-derived zinc oxide(ZnO)/Nafion has been utilized as an efficient immobilization matrix for the construction of a highly sensitive and stable tris(2,2'-bipyridyl) ruthenium(II) (Ru(${bpy)_3}^{2+})$ electrogenerated chemiluminescence (ECL) sensor. The electrochemical and ECL behaviors of Ru(${bpy)_3}^{2+})$ ion-exchanged into the composite film were strongly dependent upon the sol-gel preparation condition, the amount of MWCNT incorporated into the ZnO/Nafion composite film, and the buffer solution pH. The synergistic effect of MWCNTs and ZnO in the composite films increased not only the sensitivity but also the long-term stability of the ECL sensor. The present ECL sensor based on the MWCNT/ZnO/Nafion gave a linear response ($R^2$ = 0.999) for tripropylamine concentration from 500 nM to 1.0 mM with a remarkable detection limit (S/N = 3) of 15 nM. The present ECL sensor showed outstanding long-term stability (94% initial signal retained for 5 weeks). Since the present ECL sensor exhibits large response towards NADH, it could be applied as a transduction platform for the ECL biosensor in which the NADH is produced from the dehydrogenase-based enzymatic reaction in the presence of NA$D^+$ cofactor.

• Journal of the Korean institute of surface engineering
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• v.38 no.5
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• pp.193-197
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• 2005

Highly c-axis oriented Zinc oxide (ZnO) films were successfully deposited at room temperature by oxygen ion-assisted pulsed filtered vacuum arc. The effect of oxygen gas ratio ($O_{2}/O_{2}+Ar$ on the preferred orientation, surface morphology and resistivity of the ZnO films were investigated. Highly crystalline ZnO films with (002) orientation were obtained at over $13\%$ of oxygen gas ratio. Increasing oxygen gas ratio up to $80\%$ was found to improve crystallinity of the films. From hall measurements, it was found that the film has n-type characteristic and carrier concentration and its mobility were closely related with oxygen gas ratio. Minimal resistivity of $3.6{\times}10^{-3}{\Omega}{\cdot}cm$ was obtained in the range of $20\%$ to $40\%$ of oxygen gas ratio.

• Journal of the Korean institute of surface engineering
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• v.44 no.6
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• pp.250-254
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• 2011

NiO-AZO films were deposited on glass substrate by DC and RF magnetron co-sputtering system in pure $O_2$ gas without substrate heating during deposition. In order to control the chemical composition of the film, NiO target was supplied with constant RF power of 150 W and AZO target (doped with 2.98 at% aluminum) with DC power varied between 40 W to 80 W. Deposited NiO-AZO films were evaluated by structural and chemical analysis. With introducing AZO, XRD and XPS data reveal that NiO were supplied with more oxygen. these results could be strongly affected by the higher bond enthalpy of NiO compared to ZnO, which makes it possible for NiO to obtain excessive oxygen from ZnO.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.876-881
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• 2011

The sintering, defect and grain boundary characteristics of Bi-based ZnO chip varistor (1,608 mm size) have been investigated to know the possibility of lowering a manufacturing price by using 100 % Ag inner-electrode. The samples were prepared by general multilayer chip varistor process and characterized by shrinkage, SEM, current-voltage (I-V), admittance spectroscopy (AS), impedance and modulus spectroscopy (IS & MS) measurement. There are no problems to make a chip varistor with 100% Ag inner-electrode in the sintering temperature range of 850~900$^{\circ}C$ for 1 h in air. A good varistor characteristics ($V_n$= 9.3~15.4 V, a= 23~24, $I_L$= 1.0~1.6 ${\mu}A$) were revealed but formed $Zn_i^{{\cdot}{\cdot}}$(0.209 eV) as dominant defect, and increased the distributional inhomogeneity and the temperature instability in grain boundary barriers.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.256-256
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• 2010

투명전극부터 디스플레이 산업에 이르기까지 광범위하게 응용되어지고 있고 개발되어지고 있는 투명전도산화물(TCO)은 ZnO, In2O3, SnO2 등을 기본으로 하는 n-type 재료가 대부분이다. 그러나 투명전도 산화물을 이용한 light emitting diode(LED), 투명한 태양전지, p-형 TFT와 같은 투명전자소자의 개발을 위해서는 p-type 소재가 필수적이다. p-type TCO 소재는 비교적 연구 개발 실적이 매우 부진한 실정이었다. 1997년 넓은 밴드갭을 가지는 ABO2(delafossite) 산화물이 p-type으로서 안정적이라는 것을 보고함에 따라 이에 대한 연구가 활발히 진행되고 있다. 현재 ABO2 형태를 가진 Delafossite구조 산화물이 가장 유망한 p-type 투명전도체 소재로 거론되고 있다. Delafossite 구조가 p-type 투명전도체에 적합한 결정구조인 이유는 밴드갭이 넓고 공유결합에 유리하기 때문이다. Delafossite구조는 상온에서 2종류의 polytype(상온에서 Rhombohedaral구조와 hexagonal 구조)이 존재하며 이들은 각각 3R 및 2H의 결정 구조를 가지고 있다. ABO2의 delafossite구조에서 Cu+의 배열은 c-축을 따라 Cu-O-Cr-O-Cu의 연속적인 층 구조로서 2차원연결로 보여 진다. 보고된 Cu- base delafossite구조를 가지는 재료들은 CuAlO2, CuGaO2, CuInO2 등 여러가지가 있다. 본 연구에서는 PLD를 이용하여 c-plane 사파이어 기판위에 성장된 delafossite구조인 CuCrO2박막의 특성을 알아보았다. p-type 특성을 위하여 CuCrO2에 Zn를 첨가하였으며 그에 따른 구조적 전기적 특성을 조사하였다. 성장온도와 산소분압을 $500{\sim}700^{\circ}C$, 0~10mTorr로 변화시켜 특성을 연구하였다. 성장온도 $700^{\circ}C$, 산소분압 10mTorr에서 c-plane 사파이어 기판위에 c-축 배향의 에피성장된 CuCrO2:Zn 박막을 얻을 수 있었다. Mg를 도핑함에 따른 p-type 특성보다 현저히 떨어지는 것을 확인하였다. 또한 동일한 조건임에도 특정한 이차상의 존재를 통해 도핑된 Zn의 위치를 추측할 수 있었다. 온도와 분압에 따른 결정성과 표면상태를 SEM을 통해서 확인하였다.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.177-185
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• 2022

Electrochemical properties of LiMn₂O₄ cathode were investigated in three types of Zn-containing electrolytes: lithium-zinc sulfate electrolyte (1M ZnSO₄ / 2M Li₂SO₄), zinc sulfate electrolyte (2MZnSO₄) and lithium-zinc-manganese sulfate electrolyte (1MZnSO₄ / 2MLi₂SO₄ / 0.1MMnSO₄). Cyclic voltammetry measurements demonstrated that LiMn₂O₄ is electrochemically inactive in pure ZnSO₄ electrolyte after initial oxidation. The effect of manganese (II) additive in the zinc-manganese sulfate electrolyte on the electrochemical performance was analyzed. The initial capacity of LiMn₂O₄ is higher in presence of MnSO₄ (140 mAh g^-1 in 1 M ZnSO₄ / 2 M Li₂SO₄ / 0.1 M MnSO₄ and 120 mAh g^-1 in 1 M ZnSO₄ / 2MLi₂SO₄). The capacity increase can be explained by the electrodeposition of MnO_x layer on the electrode surface. Structural characterization of postmortem electrodes with use of XRD and EDX analysis confirmed that partially formed in pure ZnSO₄ electrolyte Zn-containing phase leads to fast capacity fading which is probably related to blocked electroactive sites.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.127.2-127.2
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• 2011

본 연구에서는 RF Magnetron Sputtering System을 이용하여 ZnO계 투명전도막 증착시 Vaporization된 MeOH를 유입함으로써 박막증착과 동시에 표면의 Roughness를 제어하여 이에따른 전기적 특성 및 광학적 특성의 개선에 대하여 연구하였다. 실험방법으로 기존의 RF Magnetron Sputtering System에 Vaporization이 가능한 Ultrasonic을 이용하여 MeOH를 Vaporized시켜 MFC Controll을 통해 챔버에 유입하여 ZnO계 투명전도막의 박막증착과 동시에 표면 Texturing을 하였다. ZnO계 투명전도막의 박막증착시 Vaporized MeOH의 유입에 따른 광학적 특성변화를 UV-visible-nIR spectrometry로 조사하였으며, 전기적 특성 변화를 4-Point-Probe로 조사하였으며, 표면적 특성 변화를 Atomic Force Microscope(AFM), Scanning Electron Microscopy(SEM)를 조사하였으며, 박막의 결정성장특성 변화를 X-ray Diffraction(XRD)으로 조사하였으며, Vaporized MeOH 유입에 따른 박막의 성분분석을 Secondary Ion Mass Spectrometry (SIMS)로 조사함으로써 최적의 조건 및 공정을 확립하였다.