• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.428-432
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• 2017

Silicon 기반 Metal-oxide-semiconductor field-effect transistor (MOSFET)의 크기가 감소함에 따라 silicon자체의 물성적 한계가 나타나고 있다. 이를 극복하고자 III-V 화합물 반도체가 채널소자로서 각광받고 있다. 본 연구에서는 III-V 화합물반도체 중 $In_xGa_{1-x}As$는 Indium 조성에 따른 전자구조 및 n-type MOSFET의 소자 특성을 본다. Indium의 조성이 증가함에 따라 subband의 개수와 간격이 증가하게 되어 Density of state가 감소하게 된다. 이로 인하여 Indium의 조성이 증가함에 따라 $In_xGa_{1-x}As$ 채널 MOSFET에서 상대적으로 Fermi level을 더 많이 상승시키게 되어 potential barrier를 얇아지게 만들며 또한 에너지에 따른 전류 밀도를 넓게 분포하도록 만든다. 이로 인하여 단채널에서는 In 조성이 증가함에 따라 direct source-to-drain tunnelling current이 증가하게 된다. 이로 인하여 In 조성의 증가에 따라 subthreshold swing과 ON-state current가 저하된다.

• Journal of the Semiconductor & Display Technology
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• v.4 no.3 s.12
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• pp.35-38
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• 2005

Due to high permeability of the ferrite cores, the characteristics of the inductively coupled plasma(ICP) are expected to be greatly improved. We investigated the effect of the ferrite cores on conventional inductively coupled plasma. It was observed that the current and voltage in the ICP antenna are slightly decreased and the power transfer efficiency is increased. However, due to eddy current and hysteresis loss, plasma density in the ICP with the ferrite cores is not increased. It seems that the ICP with the ferrite cores at low frequency ($\∼$100 kHz) will be greatly improved since the losses at the low frequency can be negligible.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.23-27
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• 2005

A fluorescent lamp which uses low pressure mercury-argon gas discharge shows the maximum current and minimum lamp voltage near 1(kHz) source frequency at constant power. For explain these phenomena theoretically, in this paper a atomic level discharge model was made and particle density and electron temperature variation were calculated using numerical method.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.88-88
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• 2010

The liquid metal ion sources(LMIS) in FIB system have many advantages of high current density, high brightness, and low ion energy spread. Most FIB systems use LMIS because the beam spot size of LMIS is smaller than of gas field ionization sources(GFIS). LMIS basically consists of a emitter(needle, anode), a reservoir(gallium) and a extractor(cathode). But several LMIS have new electrode called the suppressor. We investigated characteristics of LMIS with a suppressor. The characteristics of the threshold voltage and current-voltage (I-V) were observed under the varying extracting voltage with floated suppressor voltage, and under the varying suppressor voltages with fixed extractor voltage. We also simulated LMIS with the suppressor through CST(Computer Simulation Technology). We can explain characteristics of LMIS with a suppressor using the electric field.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.197-202
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• 2005

Due to high permeability of the ferrite core, the characteristics of the ICP are expected to be greatly improved. We investigated the effect of the ferrite cores on conventional inductively coupled plasma. It was observed that the current and voltage in ike ICP antenna are slightly decreased and the power transfer efficiency is increased. However, due to eddy current and hysterisis loss, plasma density in the ICP with the ferrite cores is not increased. It seems that the ICP with the ferrite cores at low frequency (${\~}$100kHz) will be greatly improved since the losses at the low frequency can be negligible.

• Current Optics and Photonics
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• v.5 no.2
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• pp.129-133
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• 2021

This study observed the performance of an InAs/GaSb type-II superlattice photodiode with a p-i-n structure for mid-wavelength infrared detection. The 10 ML InAs/10 ML GaSb type-II superlattice photodiode was grown using molecular beam epitaxy. The cutoff wavelength of the manufactured photodiode with Si3N4 passivation on the mesa sidewall was determined to be approximately 5.4 and 5.5 ㎛ at 30 K and 77 K, respectively. At a bias of -50 mV, the dark-current density for the Si3N4-passivated diode was measured to be 7.9 × 10-5 and 1.1 × 10-4 A/㎠ at 77 K and 100 K, respectively. The differential resistance-area product RdA at a bias of -0.15 V was 1481 and 1056 Ω ㎠ at 77 K and 100 K, respectively. The measured detectivity from a blackbody source at 800 K was calculated to be 1.1 × 1010 cm Hz1/2/W at zero bias and 77 K.

• Analytical Science and Technology
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• v.22 no.5
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• pp.355-359
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• 2009

An enzyme electrode bound by rubber solution was newly constructed and the test of its practicability were carried out. The binder of carbon powder was styrene-butadiene rubber dissolved in toluene and enzyme source was ground tissue of cabbage root. Volatilization of the solvent made the electrode material possess a mechanical robustness and a fast signal appearance. The electrode showed electrochemically irreversible characteristics and a powerful catalytic power (detection limit=$5.0{\times}10^{-5}M$, S/N=2). The double reciprocal plot of signal current and substrate concentration was ideally linear and the symmetry factor and exchange current density of the electrode used in this work were 0.35 and $4.93{\times}10^{-5}Acm^{-2}$ respectively.

• Advances in nano research
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• v.12 no.1
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• pp.25-35
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• 2022

Within the framework of the density functional theory combined with the method of non-equilibrium Green's functions (DFT + NEGF), the features of electron transport in fullerene nanojunctions, which are «core-shell» nanoobjects made of a combination of fullerenes of different diameters C₂₀, C₈₀, C₁₈₀, placed between gold electrodes (in a nanogap), are studied. Their transmission spectra, the density of state, current-voltage characteristics and differential conductivity are determined. It was shown that in the energy range of -0.45-0.45 eV in the transmission spectrum of the "Au-C₁₈₀-Au" nanojunction appears a HOMO-LUMO gap with a width of 0.9 eV; when small-sized fullerenes C₂₀, C₈₀ are intercalation into the cavity C₁₈₀ the gap disappears, and a series of resonant structures are observed on their spectra. It has been established that distinct Coulomb steps appear on the current-voltage characteristics of the "Au-C₁₈₀-Au" nanojunction, but on the current-voltage characteristics "Au-C₈₀@C₁₈₀-Au", "Au-(C₂₀@C₈₀)@C₁₈₀-Au" these step structures are blurred due to a decrease in Coulomb energy. An increase in the number of Coulomb features on the dI/dV spectra of core-shell fullerene nanojunctions was revealed in comparison with nanojunctions based on fullerene C₆₀, which makes it possible to create high-speed single-electron devices on their basis. Models of single-electron transistors (SET) based on fullerene nanojunctions "Au-C₁₈₀-Au", "Au-C₈₀@C₁₈₀-Au" and "Au-(C₂₀@C₈₀)@C₁₈₀-Au" are considered. Their charge stability diagrams are analyzed and it is shown that SET based on C₈₀@C₁₈₀-, (C₂₀@C₈₀)@C₁₈₀- nanojunctions is output from the Coulomb blockade mode with the lowest drain-to-source voltage.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.719-720
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• 2004

A multi-megawatt long pulse ion source (LPIS) of neutral beam injector was developed for the KSTAR. Beam extraction experiments of the LPIS were carried out at the neutral beam test stand (NBTS). Design requirements for the ion source were 120 kV/65 A deuterium beam and a 300 s pulse length. A maximum ion density of $9.1310^{11}$ $cm^{-3}$ was measured by using electric probes, and an optimum arc efficiency of 0.46 A/kW was estimated with ion saturation current of the probes, arc power, and total beam area. An arcing problem, caused by the structural defect of decelerating grid supporter, in the third gap was solved by the blocking of backstream ion particles, originated from the plasma in the neutralizer duct, through the unnecessary spaces on the side of grid supporter. A maximum drain power of 1.5 MW (i.e. 70 kV/21 A) with hydrogen was measured for a pulse duration of 0.5 s. Optimum beam perveance was ranged from 0.75 to 0.85. An improved design of accelerator for the effective control of beam particle trajectory should provide higher beam perveance.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.373-375
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• 2008

Studying for environmentally-friendly and efficient energy source is now actively under way on because problems like environmental pollution and exhaust of natural resources are in issue. Pure Cell which is an alternative energy source has low voltage and high current characteristic, therefore boost up voltage converter and DC-AC converter is required to use as a common power source. In this paper, DC-DC converter which has high efficient and high power density is proposed and verified by experimental result.