• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.70-73
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• 1997

The purpose of this study is to research and develop poly(p-phenylene)(PPP)-based carbon obtained by pyrolyzing electrochemically prepared PPP as a anode of rocking chair batteries. Disordered carbon materials were obtains by heat-treating of PPP films in a nitrogen atmosphere at 4$0^{\circ}C$ to 110$0^{\circ}C$ for 1 hour. The carbon prepared by heat treatment showed a broad x-ray diffraction peak having characteristics of disordered carbon. Carbon electrodes were charged and discharged at a current density of 0.1㎃/$\textrm{cm}^2$. First discharge capacity of 267㎃h/g and 34% of charge/discharge efficiency were observed from PPP-based carbon prepared at $700^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.373-377
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• 1996

Carbon materials have become a major interestings of research directed toward the development for anode of lithium batteries of enhanced cell capacity. The purpose of this study is to research and develop poly(p-phenylene)(PPP)-based carbon as a anode of lithium secondary batteries. We have synthesized PPP from benzen by chemical reaction. And then disordered carbon materials were obtained by heat-treating PPP in a nitrogen atmosphere at 40$0^{\circ}C$ to 100$0^{\circ}C$ for 1 hour. The carbon prepared by heat treatment showed a broad x-ray diffraction peak around 2$\theta$=23$^{\circ}$. Electrodes were charged and discharged at a current density of 0.1㎃/$\textrm{cm}^2$. Excellent reversible capacity of 275㎃h/g and 97% of charge/discharge efficiency were observed heat treated PPP-based carbon a $700^{\circ}C$.

• Current Optics and Photonics
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• v.2 no.4
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• pp.378-382
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• 2018

In most previous investigations of plasmonic and metamaterial applications, the metallic film has been regarded as a perfect electrical conductor. Here we demonstrate the resonance characteristics of THz metamaterials fabricated from metal film that has a finite dielectric constant, using finite-difference time-domain simulations. We found strong redshift and spectral broadening of the resonance as we decrease the metal's plasma frequency in the Drude free-electron model. The frequency shift can be attributed to the effective thinning of the metal film, originating from the increase in penetration depth as the plasma frequency decreases. On the contrary, only peak broadening occurs with an increase in the scattering rate. The metal-thickness dependence confirms that the redshift and spectral broadening occur when the effective metal thickness drops below the skin-depth limit. The electromagnetic field distribution illustrates the reduced field enhancement and reduced funneling effects near the gap area in the case of low plasma frequency, which is associated with reduced charge density in the metal film.

• ETRI Journal
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• v.31 no.6
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• pp.642-646
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• 2009

Highly efficient white phosphorescent organic light-emitting diodes with a mixed-host structure are developed and the device characteristics are studied. The introduction of a hole-transport-type host (N, N'-dicarbazolyl-3-3-benzen (mCP)) into an electron-transport-type host (m-bis-(triphenylsilyl)benzene (UGH3)) as a mixed-host emissive layer effectively achieves higher current density and lower driving voltage. The peak external quantum and power efficiency with the mixed-host structure improve up to 18.9% and 40.9 lm/W, respectively. Moreover, this mixed-host structure device shows over 30% enhanced performance compared with a single-host structure device at a luminance of 10,000 $cd/m^2$ without any change in the electroluminescence spectra.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.415-417
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• 2009

Color stable and efficient two wavelength white organic light emitting diodes (OLEDs) were fabricated using a iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,$C^2$'] picolinate (FIrpic) as a blue phosphorescent emitter and a bis(1-phenylisoquinolinato-$C^2$,N)iridium (acetylacetonate) ((piq)$_2$Ir(acac)) as a red phosphorescent emitter. The emitting layers consist of two blue emitting layers and one red emitting layer which is between the two blue layers. The device reaches the peak efficiencies of 7.84 % and 10.3 cd/A at 0.6 mA/$cm^2$. Furthermore, there was little change of EL spectra according to current density change in the device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.587-595
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• 1998

Transient thermal analysis simulations are carried out using a modeling program to understand the human body model HBM ESD. The devices were simulated a one-dimensional device subjected to ESD stress by solving Poison's equation, the continuity equation, and heat flow equation. A ramp rise with peak ESD voltage during rise time is applied to the device under test and then discharged exponentially through the device. LDD and NMOS structures were studied to evaluate ESD performance, snap back voltages, device heating. Junction heating results in the necessity for increased electron concentration in the space charge region to carry the current by the ESD HBM circuit. The doping profile adihacent to junction determines the amount of charge density and magnitude of the electric field, potential drop, and device heating. Shallow slopes of LDD tend to collect the negative charge and higher potential drops and device heating.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.65-70
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• 2014

This paper presents the simulation and design of an all-optical subtractor using a quantum-dot semiconductor optical amplifier Mach-Zehnder interferometer (QD-SOA MZI) structure consisting of two cascaded switches, the first of which produces the differential bit. Then the second switch produces the borrow bit by using the output of the first switch and the subtrahend data stream. Simulation results were obtained by solving the rate equations of the QD-SOA. The effects of QD-SOA length, peak power and current density have been investigated. The designed gate can operate at speeds of over 250 Gb/s. The simulation results demonstrate a high extinction ratio and a clear and wide-opening eye diagram.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.608-616
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• 1995

Porous silicon (PS) was prepared under different anodization conditions and the photoluminescence (PL) was measrued. In addition PL of the naturally and thermally oxidized PS was measured. It was found that the PL peak was shifted to shorter wavelength as the anodization current density and the extent of the oxidation increased. The absence of correlation between the PL behavior and the surface hydrogen species (Si-H2, Si-H) implies that the mechanism of PL of PS is not likely related to the surface hydrogen species effect but to the quantum confinement effect.

• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.154-158
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• 2010

Numerical analysis is done to investigate the effects of pulse bias on the plasma processing characteristics like ion doping and ion nitriding by using fluid dynamic code with a 2D axi-symmetric model. For 10 mTorr of Ar plasma, -1 kV of pulse bias was simulated. Maximum sheath thickness was around 20 mm based on the electric potential profile. The peak electron temperature was about 20 eV, but did not affect the averaged plasma characteristics of the whole chamber. Maximum ion current density incident on the substrate was 200 $A/m^2$ at the center, but was decreased down to 1/10th at radius 100 mm, giving poor radial uniformity.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.125-125
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• 2018

반도체 소자의 미새화에 따라 선폭이 10nm 이하로 줄어듦에 따라, 금속 배선의 저항이 급격하게 상승하고 있다. Cu는 낮은 저항과 높은 전도도를 가지고 있어 현재 배선물질로써 가장 많이 사용되고 있지만, 소자가 미세화됨에 따라 Cu를 미래의 배선물질로써 계속 사용하기에는 몇 가지 문제점이 제기되고 있다. Cu는 electron mean free path (EMFP)가 39 nm로 긴 특성을 가지기 때문에, 선폭이 줄어듦에 따라 surface 및 grain boundary scattering이 증가하여 저항이 급격하게 증가한다. 또한, technology node에 따른 소자의 operating temperature와 current density의 증가로 인해 Cu의 reliability가 감소하게 된다. 텅스텐은 EMFP가 19 nm로 짧은 특성을 가지고 있어, 소자의 크기가 줄어듦에 따라 Cu보다 낮은 저항 특성을 가질 수 있으며, 녹는점이 3695K로 1357K인 Cu보다 높으므로 배선물질로써 Cu를 대체할 가능성이 있다. 본 연구에서는 Inductively Coupled Plasma (ICP) assisted magnetron sputtering을 통해 매우 얇은 텅스텐 박막을 증착하여 저항을 낮추고자 하였다. 고밀도 플라즈마의 방전을 위해, internal-type coil antenna를 사용하였으며 텅스텐 박막의 증착을 위해 DC sputter system이 사용되었다. 높은 에너지를 가진 텅스텐 이온을 이용하여 낮은 온도에서 고품위 박막을 증착할 수 있었으며, dense한 구조의 박막 성장이 가능하였다. ICP assisted를 이용하여 증착했을 때와, 그렇지 않을 때를 비교하여 ICP 조건에 따라서 박막의 저항이 감소함을 확인할 수 있었을 뿐만 아니라 최대 약 65% 감소함을 확인할 수 있었다. XRD를 이용하여 ICP power를 인가했을 때, 높은 저항을 갖는 A-15 구조를 가진 ${\beta}$ peak의 감소와 낮은 저항을 갖는 BCC 구조를 가진 ${\alpha}$ peak의 증가를 상온과 673K에서 증착한 박막 모두에서 확인하였으며, 이를 통해 ICP power가 저항 감소에 영향을 미친다는 것을 확인하였다. 또한, 두 온도 조건에서 grain size를 계산하여 ICP power를 인가함에 따라 두 조건 모두 grain size가 증가하였음을 조사하였다. 또한, XPS 분석을 통해 ICP power를 인가하였을 때 박막의 저항에 많은 영향을 끼치는 O peak이 감소하는 것을 통해 ICP assisted의 효과를 확인하였다. 이를 통해, ICP assisted magnetron sputtering을 통해 텅스텐 박막을 증착함으로써 차세대 배선물질로써 텅스텐의 가능성을 확인할 수 있었다.