• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.469-469
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• 2010

공정 플라즈마에서 가장 중요한 요소 중 하나는 챔버 내 균일도 제어이다. 챔버 내 플라즈마 상태가 공간적으로 불균일한 경우 과에칭, 미증착 등의 문제가 웨이퍼의 특정 영역에 나타나게 되어 공정 수율이 감소된다. 이 연구에서는 2차원 평면 탐침을 챔버 내에 삽입하여 플라즈마 전자온도, 밀도, 이온 전류량 등의 상태변수를 측정 가능한 방법을 연구하였다. 기존의 2차원 평면 탐침과 달리, 측정 회로와 계산 모듈을 모두 삽입하여 외부의 컨트롤러가 필요 없어 반도체나 디스플레이의 플라즈마 공정의 사이사이에 삽입되어서 플라즈마 상태변수를 측정할 수 있는 장점을 가지고 있다. 본 임베디드 2차원 평면 탐침은 측정회로가 외부와 단절되어 전기적으로 절연되어 있어, 측정 방법으로 이중 탐침법을 응용하였다. 이중탐침에 정현파 전압을 인가하고 이 경우 들어오는 전류의 제 1 고조파와 제 3 고조파를 크기를 측정하는 방법으로 플라즈마 변수 계산이 가능하다. 이 측정 방법은 플라즈마 공정에서 쉽게 관찰할 수 없었던 공간적인 상태변수의 분포를 알 수 있고 플라즈마 균일도 제어에 기여할 수 있을 것이다.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.562-565
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• 2013

The high purity Al foil, which has an enlarged surface area by electrochemical etching process, has been used as an anode for an aluminum electrolytic capacitor. Etch pits are randomly distributed on the surface because of the existence of surface irregularities such as impurity and random nucleation of pits. Even though a large surface area was formed on the tunnel-etched Al, its applications to various fields were limited due to non-uniform tunnel morphologies. In this work, the selective electrochemical etching of aluminum was carried out by using a patterned mask fabricated by photolithographic method. The formation of etch pits with uniform distribution has been demonstrated by the optimization of experimental conditions such as current density and etching solution temperature.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.228-235
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• 2008

Nickel plating thickness increased with the electric current density, and the augmentation was more thick in $6{\sim}10A/dm^2$ than low current. Hull-cell analysis was tested to evaluate the current density. Optimum thickness was obtained at a temperature of $60^{\circ}C$, and the pH fluctuation of 3.5~4.0. Over the Nickel ion concentration of 300 g/L, plating thickness increased with the current density. The rate of decrease in nickel ion concentration was increased with the current density. The quantity of plating electro-deposition was increased at the anode surface, which was correlated with the increase of plating thickness. The plating thickness was increased because of the quick plating speed. However, the condition of the plating surface becomes irregular and the minuteness of nickel plating layer was reduced with the plating rate. After the corrosion test of 25 h, it was resulted in that maintaining low electric current density is desirable for the excellent corrosion resistance in lustered nickel plating. According to the program simulation, the thickness of diffusion layer was increased and the concentration of anode surface was lowered for the higher current densities. The concentration profile showed the regular distribution at low electric current density. The field plating process was controlled by the electric current density and the plating thickness instead of plating time for the productivity. The surface physical property of plating structure or corrosion resistance was excellent in the case of low electric current density.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.827-834
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• 2010

We have performed numerical simulations of the electrical characteristics for multi-layer organic light emitting diode devices with doped emitting layer using a commercial simulation program. In this paper, the basic structure consists of the ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al, four devices that were composed of $Alq_3$ as the host and C545T as the green dopant with different concentration, were studied. As the result, the variations of the doping concentration rate of C545T have a effect on the voltage-current density characteristics. The voltage-current characteristics are quite consistent with the results which were experimentally determined in a previous reference paper. In addition, the voltage-luminance characteristics were greatly improved, and the luminous efficiency was improved three times. In order to analyze these driving mechanism, we have investigated the distribution of electric field, charge density of the carriers, and recombination rates in the inner of the OLED devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1372-1383
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• 1998

In this paper, modeling for DC and AC characteristics analysis of DFB-LD was performed considering effects of .lambda./4-shifted gratingandspatial hole burning within a laser diode cavity. From the simulation for DC characteristics, Light-Current curve, optical power distribution and carrier density distribution within the cavity can be obtained. The simulation for AC characteristics porovides IM response and the amplitude and phase and the amplitude and phase response of FM with excellent accuracy.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.648-654
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• 2005

The performance prediction of a planar-type solid oxide fuel ceil is conducted by a computational analysis. The transport processes are formulated with the help of a simplified treatment of heat generation by the electrochemical reaction. From the result of the computational analysis, it is shown that the electrochemical reaction is closely related to the transport phenomena inside a solid oxide fuel cell. Transport phenomena including heat and mass transfer have influence on the distribution of local current density and as a result, on the performance characteristics of the fuel cell. Computational analysis is also extended to the parametric study to investigate the performance behavior of the fuel cell with different amount of supplied fuel flow rates. It is also demonstrated that the mathematical formulation and computational procedures proposed in this study can be applied to prove the importance of the specific TPB(Three-Phase-Boundary) area in the manufacturing process of electrodes in a solid oxide fuel cell.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.7
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• pp.763-768
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• 2015

In this paper, a microstrip patch antenna with arrow and ribbon shape for WLAN was designed and manufactured. The antenna was designed on a FR-4 substrate that has a thickness of 0.8mm and a dielectric constant of 4.4. The substrate size is $50{\times}40mm^2$. A commercially available tool was used for simulation to get the optimized parameters and the optimized values were obtained by finding the parameters that act sensitively to the performance of the antenna. The proposed antenna was produced using the optimized values, and characteristics of return loss, gain and radiation pattern in WLAN bands were measured.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.604-612
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• 2009

Water management has been recognized as a crucial factor for achieving better performance and stability in polymer electrolyte membrane fuel cells (PEMFCs). Proper water management should provide favorable water conditions, including the local humidity, membrane water content, and liquid water saturation in PEMFCs, thereby leading to more uniform electrochemical reaction and current generation. In this study, computational fluid dynamics (CFD) simulation was conducted to investigate the effects of the cathode relative humidity (RH) on the performance of a 3 by $3\;cm^2$ PEMFC with serpentine flow fields. The CFD results showed that the best performance of the PEMFC was obtained for the cathode RH of 80%, but the performance variation was small for the cathode RH range of $60{\sim}100%$. However, the loss of the PEMFC performance was significant when the cathode RH was reduced below 40%. The reason for such performance variation was investigated through the detailed inspection of ohmic loss, activation and concentration overpotential, and water and current distributions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.321-332
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• 2017

In order to build a general model of a high-throughput uranium electrorefining process according to the electrode configuration, numerical analysis was conducted using the COMSOL Multiphysics V5.3 electrodeposition module with Ordinary Differential Equation (ODE) interfaces. The generated model was validated by comparing a current density-potential curve according to the distance between the anode and cathode and the electrode array, using a lab-scale (1kg U/day) multi-electrode electrorefiner made by the Korea Atomic Energy Research Institute (KAERI). The operating temperature was $500^{\circ}C$ and LiCl-KCl eutectic with 3.5wt% $UCl_3$ was used for molten salt. The efficiency of the uranium electrorefining apparatus was improved by lowering the cell potential as the distance between the electrodes decreased and the anode/cathode area ratio increased. This approach will be useful for constructing database for safety design of high throughput spent nuclear fuel electrorefiners.

• Journal of Digital Convergence
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• v.12 no.7
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• pp.291-296
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• 2014

Inserting a $SiO_2$ layer underneath the p-pad electrode as the current blocking layer (CBL) structure and extending p-metal finger patterns, the GaN LEDs using an indium-tin-oxide (ITO) layer show the improved light output intensity, resulting from better current spreading and reduced light loss on the surface of p-pad metal. The LEDs with an oxide layer of $100{\mu}m$-pad-width and $6{\mu}m$-finger-width have better light output intensities than those with an oxide layer of $105{\mu}m$-pad-width and $12{\mu}m$-finger-width. Using the ATLAS device simulator from Silvaco Corporation, the current density distributions on the active layer in CBL LEDs have been investigated.