• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1321-1322
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• 2007

$Ar/Cl_2$, $Ar/CH_4$ 및 $Ar/Cl_{2}/CH_{4}$ 유도결합 플라즈마의 가스 혼합비에 따른 BLT 박막의 식각 메커니즘과 선택비, 식각 후 박막 표면의 조성변화를 조사하였다. BLT 박막의 최대식각률은 $Ar/Cl_2$ 플라즈마에서의 Ar 가스 혼합비가 80%일 때 50.8 nm의 값을 보였다. 이 때, 1sccm의 $CH_4$ 첨가를 통하여 선택비와 식각률을 개선할 수 있었다. 박막 표면의 xPS 분석을 통해 BLT 박막 표면의 조성변화는 Cl 원자와의 반응에 의한 화학적 식각 손상이 H 원자와의 반응에 의한 그것보다 크다는 것을 알 수 있었다.

• Membrane Journal
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• v.23 no.1
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• pp.54-60
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• 2013

PEGDA/PETEDA dendrimer composite membranes was prepared by UV photopolymerizing of poly ethylene glycol diacrylate (PEGDA) containing 5~15 wt% pentaerythrityl tetraethylenediamine (PETEDA) dendrimer. The prepared composite membrane was characterized by FT-IR, $^1H$-NMR and DSC. The glass transition temperature ($T_g$) of PEGDA/PETEDA dendrimer composite decreased with the increment of PETEDA dendrimer content. The $CO_2$ separation properties over $CH_4$ were investigated by changing the PETEDA dendrimer content and pressure. The composite membrane containing 10 wt% PETEDA dendrimer exhibited on excellent $CO_2/CH_4$ ideal selectivity of 31.8 and a $CO_2$ permeability of 162.2 barrer.

• Journal of Magnetics
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• v.12 no.2
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• pp.81-83
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• 2007

Etching of NiFe films covered with an organic photo-resist or Ti was successfully performed by an inductively coupled plasma-reactive ion etching (ICP-RIE) system using $CHF_3/O_2/NH_3$ discharges exchanging $CHF_3$ for $CH_4$ gas gradually. Experimental results showed that the organic photo-resist mask can be applied to the NiFe etching. In the case of the Ti metal mask, it was found that the etching-selectivity Ti against NiFe was significantly varied from 7.3 to ${\sim}0$ by changing $CHF_3/CH_4/O_2/NH_3$ to $CH_4/O_2/NH_3$ discharges used in the ICP-RIE system. These results show that the present RIE of NiFe was dominated by a chemical reaction rather than a physical sputtering.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.297-303
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• 2019

A triple-layered $PMMA/Ni_{64}Zr_{36}/PDMS$ hydrogen gas sensor using hydrogen permeable alloy and flexible polymer layers is fabricated through spin coating and DC-magnetron sputtering. PDMS(polydimethylsiloxane) is used as a flexible substrate and PMMA(polymethylmethacrylate) thin film is deposited onto the $Ni_{64}Zr_{36}$ alloy layer to give a high hydrogen-selectivity to the sensor. The measured hydrogen sensing ability and response time of the fabricated sensor at high hydrogen concentration of 99.9 % show a 20 % change in electrical resistance, which is superior to conventional Pd-based hydrogen sensors, which are difficult to use in high hydrogen concentration environments. At a hydrogen concentration of 5 %, the resistance of electricity is about 1.4 %, which is an electrical resistance similar to that of the $Pd_{77}Ag_{23}$ sensor. Despite using low cost $Ni_{64}Zr_{36}$ alloy as the main sensing element, performance similar to that of existing Pd sensors is obtained in a highly concentrated hydrogen atmosphere. By improving the sensitivity of the hydrogen detection through optimization including of the thickness of each layer and the composition of Ni-Zr alloy thin film, the proposed Ni-Zr-based hydrogen sensor can replace Pd-based hydrogen sensors.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.32-38
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• 2021

We developed an inductively coupled plasma (ICP) etcher for GaN etching using a parallel plasma electrode source with a multifunctional chuck matched to it in order for the low power consumption and low process cost in comparison with the conventional ICP system with a helical-type plasma electrode source. The optimization process condition using it for the micro light-emitting diode (µ-LED) chip fabrication was established, which is an ICP RF power of 300 W, a chuck power of 200 W, a BCl₃/Cl₂ gas ratio of 3:2. Under this condition, the mesa structure with the etch depth over 1 ㎛ and the etch angle over 75° and also with no etching residue was obtained for the µ-LED chip. The developed ICP showed the improved values on the process pressure, the etch selectivity, the etch depth uniformity, the etch angle profile and the substrate temperature uniformity in comparison with the commercial ICP. The µ-LED chip fabricated using the developed ICP showed the similar or improved characteristics in the L-I-V measurements compared with the one fabricated using the conventional ICP method

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.36-43
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• 2022

Breakthrough analysis has widely been explored for the dynamic separation of gaseous mixtures in porous materials. In general, breakthrough experiments measure the components of a flowing gas when a gaseous mixture is injected into a column filled with an adsorbent material. In this paper, we report on the design and fabrication of a breakthrough curve measurement device to study the dynamic adsorptive separation of hydrogen isotopologues in porous materials. Using the designed system, an experiment was conducted involving a 1:1 mixture of hydrogen and deuterium passed through a column filled with zeolite 13X (1 g). At room temperature, both hydrogen and deuterium were adsorbed in negligible amounts; however, at a temperature of 77 K, deuterium was preferentially adsorbed over hydrogen. The selectivity was different from that in the existing literature due to the different sample shapes, measurement methods, and column structures, but was at a similar level to that of cryogenic distillation (1.5).

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.57-64
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• 2020

The water-gas shift reaction for the compact reformer was carried out at a gas hourly space velocity of 72,152 h^-1 over the Cu-Nb-CeO₂ catalysts prepared by co-precipitation method. In order to investigate the effect of Nb₂O₅ promotion over a Cu-CeO₂ catalyst, the Nb₂O₅ loading amount was systematically changed from 0 to 5 wt.%. Among the prepared catalysts, the Cu-Nb-CeO₂ (1%) catalyst showed the highest catalytic activity (CO conversion=61% at 400℃) as well as 100% CO₂ selectivity. The high activity and stability of Cu-Nb-CeO₂ (1%) catalyst are correlated to high Brunauer-Emmett-Teller surface area, small metallic Cu crystallite size, and enhanced redox property.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.222-227
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• 2018

$Zn_{1-x}Co_x$ Zeolitic Imidazolate Framework (ZIF) (x = 0~0.05) were prepared by the co-precipitation of $Zn^{2+}$ and $Co^{2+}$ using 2-methylimidazole, which were converted into pure and Co-doped ZnO nanoparticles by heat treatment at $600^{\circ}C$ for 2 h. Homogeneous Zn/Co ZIFs were achieved at x < 0.05 owing to the strong coordination of the imidazole linker to $Zn^{2+}$ and $Co^{2+}$, facilitating atomic-scale doping of Co into ZnO via annealing. By contrast, heterogeneous Zn/Co ZIFs were formed at $x{\geq}0.05$, resulting in the formation of $Co_3O_4$ second phase. To investigate the potential as high-performance gas sensors, the gas sensing characteristics of pure and Co-doped ZnO nanoparticles were evaluated. The sensor using 3 at% Co-doped ZnO exhibited an unprecedentedly high response and selectivity to trimethylamine, whereas pure ZnO nanoparticles did not. The facile, bimetallic ZIF derived synthesis of doped-metal oxide nanoparticles can be used to design high-performance gas sensors.

• Membrane Journal
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• v.5 no.1
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• pp.35-43
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• 1995

For several years lots of attempts have been made to establish the liquid membrane-based techniques for separations of gas mixtures especially containing carbon dioxide. A more effective system to separate $CO_{2}$ from flue gases, a circulatory hollow-fiber membrane absorber(HFMA) consisting of absorption and desorption modules with vacuum mode, has been considered in this study. Gas-liquid mass transfer has been modeled on a membrane module with non-wetted hollow-fibers in the laminar flow regime. The influence of an absorbent flow rate on the separation performance of the circulatory HFMA can be predicted quantitatively by obtaining the $CO_{2}$ concentration profile in a tube side. The system of $CO_{2}/N_{2}$ binary gas mixture has been studied using pure water as an(inert) absorbent. As the absorbent flow rate is increased, the permeation flux(i.e., defined as permeation rate/membrane contact area) also increases. The enhanced selectivity compared to the previous results, on the other hand, shows the decreasing behavior. It has been found obviously that the permeation flux depends on the variations of pressure in gas phase of desorption module. From an accurate comparison with the results of conventional flat sheet membrane module, the advantageous permeability of this circulatory HFMA can be clearly ascertained as expected. Our efforts to the theoretical model will provide the basic analysis on the circulatory HFMA technique for a better design and process.

• Membrane Journal
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• v.21 no.3
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• pp.256-262
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• 2011

This study describes the performance of PSF and PC membranes for separation and recovery of $SF_6$ from gas mixtures (10% $SF_6$/70% $N_2$/19% $O_2$/1% $CF_4$) containing low concentration of $SF_6$. The $SF_6$ concentration in retentate, recovery efficiency and selectivity of mixed gases were measured as a function of retentate flow rate and temperature. The concentration of $SF_6$ in the gas recovered from PSF and PC membrane respectively decreased with increase of retentate flow rate and increased with increase of temperature. The values of $SF_6$ concentration in retentate of PSF membrane were higher than those of PC membrane at constant experimental conditions. The maximum value of recovery efficiency of PSF and PC membranes are 95.9% and 67.8%, respectively, under 298.15 K and 150 cc/min of retentate flow rate. With the exception of $CF_4/SF_6$, the real selectivities of $N_2/SF_6$ and $O_2/SF_6$ at PSF membrane were higher than those of PC membrane.