• 한국안전학회지
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• 제15권3호
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• pp.14-22
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• 2000

A numerical analysis has been performed on the two-dimensional rectangular gallium melting problem using the enthalpy method. The major advantage of this method is that the physical domain is discretized with fixed grids without transforming variables and the interface conditions of phase change are accounted for the definition of suitable source terms in the governing equations. But in the fixed method, there is some ambiguity in defining the porosity constant which has no physical interpretation. If the velocity correction is included in the momentum equation, for the appropriate range of porosity constant, the realistic predictions are obtained. The object of the present work is to predict the phase change within the molten steel with thin riser slab using the modified enthalpy-porosity method. The computational procedures for predicting velocity and temperature are based on the finite volume method and the non-staggered grid system. The influence of natural convection on the melting process is considered. A comparison with the experimental results shows that the modified method is better than the previous one.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 춘계학술대회 논문집
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• pp.95-95
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• 2015

IGZO (Indium Gallium Zinc Oxide) 물질은 기존에 사용되던 Amorphous Silicon에 비해 전자 이동도가 더욱 빠르기 때문에 차세대 디스플레이 재료로서 각광받고 있으며, 이러한 빠른 전자 이동도는 디스플레이 소자에 있어서 매우 중요한 요소 중 하나이다. 이를 향상시키기 위하여 본 연구에서는 ICP(inductively coupled plasma) antenna를 이용하여 rf power와 requency를 변화함으로써 박막 증착 시 발생되는 플라즈마의 특성을 조절하여, 박막의 특성을 조절하고자 했다. 이렇게 증착된 IGZO 박막은 Hall Effect Measurement를 이용하여 전기적 특성을 분석하였으며, XPS(x-ray photoelectron spectroscopy)를 이용하여 박막의 조성을 분석하였다.

• 전력전자학회논문지
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• 제25권2호
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• pp.152-155
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• 2020

This study proposes an input filter for a gallium-nitride-based direct matrix converter with a stepless current commutation technique. Various current commutation strategies have been adopted for reliable operation of switches. These strategies are complex to be implemented and require additional components. The stepless current commutation technique is simple to operate but causes overcurrent issues due to the occurrence of short circuit on input sources. In this study, to restrict the short circuit current, we utilized GaN devices with fast switching properties and modified the input filter. The proposed input filter was verified by experimental results of induction motor drive.

• Transactions on Electrical and Electronic Materials
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• 제17권4호
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• pp.235-237
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• 2016

Oxide/metal/oxide (OMO) thin films were fabricated using amorphous indium-gallium-zinc-oxide (a-IGZO) and an Ag metal layer on a glass substrate at room temperature. The optical and electrical properties of the a-IGZO/Ag/a-IGZO samples changed systemically depending on the thickness of the Ag layer. The transmittance in the visible range tends to decrease as the Ag thickness increases while the resistivity, carrier concentration, and Hall mobility tend to improve. The a-IGZO/Ag (13 nm)/a-IGZO thin film with the optimum Ag thickness showed an average transmittance (T_av) of 71.7%, resistivity of 6.63 × 10⁻⁵ Ω·cm and Hall mobility of 15.22 cm²V⁻¹s⁻¹.

• Transactions on Electrical and Electronic Materials
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• 제13권1호
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• pp.47-49
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• 2012

In this paper, we investigated the anomalous hump in the bottom gate staggered a-IGZO TFTs. During the positive bias stress, a positive threshold voltage shift was observed in the transfer curve and an anomalous hump occurred as the stress time increased. The hump became more serious in higher gate bias stress while it was not observed under the negative bias stress. The analysis of constant gate bias stress indicated that the anomalous hump was influenced by the migration of positively charged mobile interstitial zinc ion towards the top side of the a-IGZO channel layer.

• 한국전기전자재료학회논문지
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• 제27권10호
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• pp.648-652
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• 2014

We have investigated the effect of electrical properties of amorphous InGaZnO thin film transistors (a-IGZO TFTs) by post thermal annealing in $O_2$ ambient. The post-annealed in $O_2$ ambient a-IGZOTFT is found to be more stable to be used for oxide-based TFT devices, and has better performance, such as the on/off current ratios, sub-threshold voltage gate swing, and, as well as reasonable threshold voltage, than others do. The interface trap density is controlled to achieve the optimum value of TFT transfer and output characteristics. The device performance is significantly affected by adjusting the annealing condition. This effect is closely related with the modulation annealing method by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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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.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.149-150
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• 2016

본 논문은 500W급 GaN (Gallium Nitride) FET을 적용한 Full Bridge Converter 의 2차측 소자에 따른 손실을 분석한다. Diode를 적용하였을 경우의 도통손실과 Si MOSFET과 GaN FET의 스위칭 손실 및 도통손실을 분석하여 최종적인 효율 및 동기정류의 필요성을 검증하고 그에 따른 방열설계를 수식을 통해 도출하여 제안한다.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.28-33
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• 1994

The laser-assisted chemical vapor deposition (LCVD) is described, by which the growth of single-phase GaN epitaxy is achieved at lower temperatures. Trimethylgallium (TMG) and ammonia are used as source gases to deposit the epitaxial films of GaN under the irradiation of ArF excimer laser (193 nm). The as-grown deposits are obtained on c-face sapphire surface near 700$^{\circ}$C, which is substantially reduced, relative to the temperatures in conventional thermolytic processes. To overcome the lattice mismatch between c-face sapphire and GaN ad-layer, aluminum nitride(AlN) is predeposited as buffer layer prior to the deposition of GaN. The gas phase interaction is monitored by means of quadrupole mass analyzer (QMA). The stoichiometric deposition is ascertained by X-ray photoelectron spectroscopy (XPS). The GaN deposits thus obtained are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and van der Pauw method.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2016년도 임시총회 및 하계학술연구발표회
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• pp.133-133
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• 2016