• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.194-194
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• 2013

본 연구에서는 a-IGZO 활성층에 다른 dose량의 수소 이온을 조사하여 박막 트랜지스터 소자의 효과를 알아보고, 수소 이온 조사 후, 이온 조사에 따른 불안정한 소자 특성을 안정화시킬 목적으로 후 열처리에 따른 소자 특성을 알아보았다. a-IGZO 활성층에 수소이온을 110keV의 에너지로 가속하여, 수소 이온 조사량을 $1{\times}10^{14}\;ion/cm^2$, $1{\times}10^{15}\;ion/cm^2$, $1{\times}10^{16}\;ion/cm^2$로 조절하였고, 후 열처리 공정은 a-IGZO 활성층에 $1{\times}10^{16}\;ion/cm^2$ 이온조사 후, 대기 분위기로 $150^{\circ}C$, $250^{\circ}C$, $350^{\circ}C$ 각각 1시간 동안 열처리를 진행하였다. Spectroscopy Ellipsometry (SE)로 측정된 3eV이상의 광학적 밴드 갭은 기존에 보고 되었던 비정질 산화물 반도체와도 유사한 밴드 갭을 가지고 있음을 확인하였다. IGZO 박막을 활성층으로 사용하여 수소 이온 조사 공정 후 제작한 박막 트랜지스터는 3.89 $cm^2/Vs$의 전계효과이동도와 0.59V/decade의 문턱전압 이하 기울기를 보았다. 수소 이온 조사 공정을 통한 IGZO 박막 트랜지스터의 output curve가 다소 불안정함을 보였으나, $1{\times}10^{16}\;ion/cm^2$ 이온조사 후, 대기 분위기로 $150^{\circ}C$, $250^{\circ}C$, $350^{\circ}C$ 각각 1시간동안 열처리를 진행한 박막 트랜지스터의 특성은 소자의 불안정성을 보완해줄뿐만 아니라 $350^{\circ}C$ 열처리에서는 16.9 $cm^2/Vs$의 전계효과이동도와 0.33V/decade의 문턱전압 이하 기울기와 같이 더 향상된 박막 트랜지스터의 전기적 특성 결과를 관측하였다. 기존의 연구 되어진 a-IGZO 활성층에 수소이온조사와 후 열처리 공정에 따라 광학적 밴드 갭 에너지 준위의 변화와 박막 및 박막 트랜지스터 특성을 변화시킨다는 결과를 도출하였다.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.155-161
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• 2023

Ion concentration polarization (ICP) is one of the essential important mechanisms for biomolecule preconcentration devices as well as a fundamental transport phenomenon found in electrodialysis, electrochemical cell, etc. The ICP triggered by externally applied voltage enables the biomolecular analyte to be preconcentrated at an arbitrary position by a locally amplified electric field inside the microchannel. Conventional preconcentration methodologies using the ICP have two limitations: uncertain equilibrium position and hydrodynamic instability of preconcentration plug. In this work, a new preconcentration method in the dead-end microchannel around cation exchange membrane was numerically studied to resolve the limitations. As a result, the numerical model showed that the analyte was concentrated at a shock front developed in a geometrically confined dead-end channel. Furthermore, the electrokinetic behaviors for preconcentration dynamics were analyzed by changing microchannel's applied voltage and volumetric charge concentration of microchannel as key parameters to describe the dynamics. This work would provide an effective means for a point-of-care platform that requires ultra-fast preconcentration method.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.433-441
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• 2007

This work investigated the stability of a Sn-modified Pt electrode, which was used for reduction of nitrate, fabricated by an adsorption or electro-deposition of Sn on Pt. In order to find the causes for instability of the electrode, the effects of the solutions in which the electrode was used and the potential applied to the electrode on the electrochemical and metallurgical behaviors of Sn on Pt were studied. The Sn of freshly- prepared modified-Sn Pt electrode existed as Sn hydroxide form, which brought about an easy loss of the electro-activity of the electrode even staying in water, especially in acid solution. When the Sn-modified Pt electrode was used for the reduction of nitrate, the electro-activity of the electrode was affected depending on the potential applied to the electrode. When a more negative potential than the redox equilibrium potential between $Sn(OH)_2$ and Sn was applied to the electrode, the Sn hydroxide was converted to Sn that could diffused into Pt, which leaded to the loss of electro-activity of the electrode as well. The solid diffusion of Sn increased linearly with the applied potential. The Sn-electrodeposited Pt electrode which had more Sn on the electrode was more favorable to maintaining the integrity of the electrode during the reduction of nitrate than the Sn-adsorbed Pt electrode prepared in the under-potential deposition way.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.359-366
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• 2012

Zn-Air energy storage cell is an attractive type of batteries due to its theoretical gravimetric energy density, cost-effective structure and environmental-friendly characteristics. The chargeability is the most critical in various industrial applications such as smart portable device, electric vehicle, and power storage system. Thus, it is necessary to reduce large overpotential of oxygen reduction/evolution reaction, the irreversibility of Zn anode, and carbonation in alkaline electrolyte. In this review, we try to introduce recent studies and developments of bi-functional air cathode, enhanced charge efficiency via modification of Zn anode structure, and blocking side reactions applying hybrid organic-aqueous electrolyte for high power density rechargeable Zn-Air energy storage cells.

• Composites Research
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• v.18 no.3
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• pp.31-37
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• 2005

In this work, poly(ethylene oxide) (PEO) nanofibers were fabricated by electrospinning to prepare the nanofibers-reinforced composites. And the PEO powders-impregnated composites were also prepared to compare the mechanical interfacial behaviors of the composites. Morphology and fiber diameter of PEO nanofibers were determined by SEM observation. Mechanical interfacial properties of the composites were investigated in fracture toughness $(K_{IC})$ and interlaminar shea. strength (ILSS) tests. As a result, the fiber diameter was decreased with increasing the applied voltage. And optimum condition for the fiber formation was 15 kV, resulting from increasing of jet instability at high voltage. The PEO-based nanofibers-reinforced epoxy composites showed the improvements of both $K_{IC}$ and ILSS, compared to the composites impregnated with PEO powders. These results indicated that the nanofibers had higher specific surface area and larger aspect ratio than those of the powders, which played an important role in improving the mechanical interfacial properties of the composites.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.13-21
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• 2001

The discharge characteristics of 3 electrcdes AC surface discharge plasma display were analyzed. For an unstable state of the discharge which appeared at the maximum discharge voltage, it is found that a parbal erase of the wall charge by the second discharge is a cause. Based on the second discharge, new operation margin considering the interrelation between the address discharge and the display discharge was defined and the validity of it was verified by the experiments. It is necessary to decrease the acklress pulse width for high-speed addressing. However, the operation margin of the ackIress pulse decreases as the pulse width of it becomes narrower. If the address pulse width is wider than l[ps], the operation margin of the display discharge is not related to the address pulse width. From the experimental result, image or 8bit 253 gray level was displayed on PDP with the cell structure of the HDTV class by using the high-speed address ADS drive methcd with pulse width of $1[{\mu}s]$ and the brightness of $560[cd/m^2]$ was obtained. ained.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.97-102
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• 2020

Recently, various degradation mechanisms of lithium secondary battery cathode materials have been revealed. As a result, many studies on overcoming the limitation of cathode materials and realizing new electrochemical properties by controlling the degradation mechanism have been reported. Li-rich layered oxide is one of the most promising cathode materials due to its high reversible capacity. However, the utilization of Li-rich layered oxide has been restricted, because it undergoes a unique atomic structure change during the cycle, in turn resulting in unwanted electrochemical degradations. To understand an atomic structure deterioration mechanism and suggest a research direction of Li-rich layered oxide, we deeply evaluated the atomic structure of 0.4Li₂MnO₃_0.6LiNi_1/3Co_1/3Mn_1/3O₂ Li-rich layered oxide during electrochemical cycles, by using an atomic-resolution analysis tool. During a charge process, Li-rich materials undergo a cation migration of transition metal ions from transition metal slab to lithium slab due to the structural instability from lithium vacancies. As a result, the partial structural degradation leads to discharge voltage drop, which is the biggest drawback of Li-rich materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.545-549
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• 2010

Low-frequency noise (1/f noise) has been measured in order to analyze the Vth instability of ZnO TFTs having two different active layer thicknesses of 40 nm and 80 nm. Under electrical stress, it was found that the TFTs with the active layer thickness of 80 nm shows smaller threshold voltage shift (${\Delta}V_{th}$) than those with thickness of 40 nm. However the ${\Delta}V_{th}$ is completely relaxed after the removal of DC stress. In order to investigate the cause of this threshold voltage instability, we accomplished the 1/f noise measurement and found that ZnO TFTs exposed the mobility fluctuation properties, in which the noise level increases as the gate bias rises and the normalized drain current noise level($S_{ID}/{I_D}^2$) of the active layer of thickness 80 nm is smaller than that of active layer thickness of thickness 40 nm. This result means that the 80 nm thickness TFTs have a smaller density of traps. This result correlated with the physical characteristics analysis performmed using XRD, which indicated that the grain size increases when the active layer thickness is made thicker. Consequently, the number of preexisting traps in the device increases with decreasing thickness of the active layer and are related closely to the $V_{th}$ instability under electrical stress.