• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2536-2538
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• 1998

This paper investigates the residual stress of tetraethoxysilane (TEOS) and 7wt% phosphosilicate glass (PSG), which are commonly used as a sacrificial layer or etch mask in the fabrication of microelectromechanical systems (MEMS). In order to measure residual stress, $2{\mu}m$ thick TEOS and PSG stress measurement structures are fabricated. Polysilicon is used as the sacrificial layer. First the residual stress of an as-deposited 7wt% PSG flim and TEOS film are measured to be-0.3115% and -0.435%, respectively, which are quite large. These films are annealed from $500^{\circ}C$ to $800^{\circ}C$. Annealing has the effects of reducing residual stress. In the case of the 7wt% PSG film, the residual stress becomes +0.00715% after annealing at $625^{\circ}C$ for 150 minutes. In the case of TEOS film, the residual stress reduces to -0.2134% after same condition. Incidentally, this condition is the same condition for depositing a $2{\mu}m$ thick polysilicon at $625^{\circ}C$ at our low pressure chemical vapor deposition (LPCVD) furnace.

• 한국세라믹학회지
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• 제49권6호
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• pp.575-580
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• 2012

Geopolymers were synthesized using raw materials produced from two different areas: one was from Indonesia and the other was from Habcheon, Korea. The constituting phases of the Indonesian raw material were quartz and kaolinite, while those of the Habcheon sample were quartz, halloysite and albite. They were both calcined at $750^{\circ}C$ for 6 hours, and solution of NaOH and water glass was added to activate the geopolymeric reaction. The compressive strength of geopolymer synthesized from the Indonesian raw material showed a low value of $151\;kgf/cm^2$ after curing for 28 days. However, it could be greatly increased by adding blast furnace slag powders of $1188\;kgf/cm^2$ and $1969\;kgf/cm^2$ at 20 wt% and 40 wt% additions, respectively. The compressive strength of the geopolymer synthesized from the Habcheon raw material was high, at $557\;kgf/cm^2$, after 28 days, and the very high early-stage (3 days) strength of $556\;kgf/cm^2$ for this sample was remarkable. Commercially available Habcheon metastate raw material, of which composition showed low CaO and $Na_2O$ contents compared to the calcined Habcheon raw material, was also examined. It was found that the compressive strength of the commercial metastate type was nearly identical to that of the calcined Habcheon raw material except for the relatively low value at an early curing stage and at a high curing temperature of $60^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제20권7호
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• pp.594-599
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• 2007

[ $CulnS_2$ ] thin films were synthesized by sulfurization of Cu/In Stacked elemental layer deposited onto glass Substrates by vacuum furnace annealing at temperature $200^{\circ}C$. And structural and electrical properties were measured in order to certify optimum conditions for growth of the ternary compound semiconductor $CuInS_2$ thin films with non-stoichiometry composition. $CuInS_2$ thin film was well made at the annealed $200^{\circ}C$ of SLG/Cu/In/S stacked elemental layer which was prepared by thermal evaporator, and chemical composition of the thin film was analyzed nearly as the proportion of 1 : 1 : 2. Physical properties of the thin film were investigated at various fabrication conditions substrate temperature, annealing and temperature, annealing time by XRD, FE-SEM and Hall measurement system. The compositional deviations from the ideal chemical formula for $200^{\circ}C$ material can be conveniently described by non-molecularity$({\Delta}x=[Cu/In]-1)$ and non-stoichiometry $({\Delta}y=[{2S/(Cu+3In)}-1])$. The variation of ${\Delta}x$ would lead to the formation of equal number of donor and accepters and the films would behave like a compensated material. The ${\Delta}y$ parameter is related to the electronic defects and would determine the type of the majority charge carriers. Films with ${\Delta}y>0$ would behave as p-type material while ${\Delta}y<0$ would show n-type conductivity. At the sane time, carrier concentration, hall mobility and resistivity of the thin films was $9.10568{\times}10^{17}cm^{-3},\;312.502cm^2/V{\cdot}s\;and\;2.36{\times}10^{-2}\;{\Omega}{\cdot}cm$, respectively.

• 자원리싸이클링
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• 제27권6호
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• pp.38-43
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• 2018

유리생산공정에서 발생하는 요업로 전극봉인 폐주석 산화물로부터 가스환원공정과 전해정련을 통하여 고순도 주석을 회수하기 위한 연구를 수행하였다. 메탄가스 환원공정을 통해 99% 순도의 조주석을 회수하고, 불순물을 미량 제어하였다. 주석의 전해정련시 전류밀도가 $60A/dm^2$이고 전해액의 황산농도가 0.75 mol일 때 99.979%의 고순도 주석이 96.8% 회수되었다. 그리고 전극봉에 포함된 Pb, Sb 등의 독성 불순물 제어가 가능함을 확인하였다.

• 대한금속재료학회지
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• 제49권1호
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• pp.79-84
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• 2011

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at $380^{\circ}C$ for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

• 대한금속재료학회지
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• 제48권4호
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• pp.335-341
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• 2010

High-quality single-walled carbon nanotubes (SWCNTs) were synthesized by catalytic decomposition of $C_2H_2$ using Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized SWCNTs typically occurred in the form of a bundle with a diameter of 10~20 nm together with amorphous carbon and catalytic impurities, which were removed by a two-step purification process consisting of oxidation and an acid treatment. The oxidation step, using an $O_2$-Ar mixture at $380^{\circ}C$ for 5 hr in a vertical-type furnace and a $HNO_3$ treatment at $100^{\circ}C$ for one hour, was utilized to remove the amorphous carbon particles. Subsequently, metallic catalysts were removed in HCl at room temperature for 5 hr under magnetic stirring. The SWCNT suspension was prepared by dispersing the purified SWCNTs in an aqueous sodium dodecyl benzene sulfonate solution with horn-type sonication. This was then air-sprayed on glass to fabricate CNT field emitters. The samples had a turn-on field value of 4 V/${\mu}m$ and a current density of 0.67 mA/$cm^2$ at 9 V/${\mu}m$. Increasing the HCl treatment time improved the field emission properties.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.56-62
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• 2021

In this study, we created a DBD plasma device and a MnO2 catalyst mesh filter for evaluating ozone reduction of devices via the catalyst method. The DBD plasma device was manufactured by applying Ag paste to soda lime glass via the screen-printing method. The MnO2 catalyst mesh filter was manufactured by mixing MnO2 powder with binder with a 10% difference in concentration from 10% to 50% and then applying it using the dip-coating method. Finally, we sintered a MnO2 catalyst mesh filter in an electric furnace. We evaluated the characteristics of ozone generation according to the Ar gas flow of DBD plasma devices, the opening ratio, and ozone reduction performance of the MnO2 catalyst filters. Ozone reduction performance was approximately 20.4% at MnO2 10 wt%, 37.8% at MnO2 30 wt% and 50% at MnO2 50 wt%.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1855-1862
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• 2023

Graphite crucibles are used for melting uranium and its alloys in VIM furnace. Various coating materials namely Al₂O₃, ZrO₂, MgO etc. are applied on the inner surface of the crucibles using paint brush or thermal spray technique to mitigate U-C interaction. These leads to significant amount of carbon pick-up in uranium. In this study, the attempts are made to develop multilayer coatings comprising of SiC/Y₂O₃ and Mo/Y₂O₃ on graphite to study the feasibility of minimizing U-C interaction. The parameters are optimized to prepare SiC coating of about 70㎛ thickness using CVD technique on graphite coupons and subsequently Y₂O₃ coating of about 250㎛ thickness using plasma spray technique. Molybdenum and Y₂O₃ layers were deposited using plasma spray technique with 70㎛ and 250㎛ thickness, respectively. Interaction studies of the coated graphite with molten uranium at 1450℃ for 20 min revealed that Y₂O₃ coating with SiC interlayer provides physical barrier for uranium-graphite interaction, however, this led to the physical separation of coating layer. Y₂O₃ coating with Mo interlayer provided superior barrier effect showing no degradation and the coatings remained intact after interaction tests. Therefore, the Mo/Y₂O₃ coating was found to be a promising solution for minimizing carbon pick-up during uranium/uranium alloy melting.

• 한국진공학회지
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• 제22권5호
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• pp.238-244
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• 2013

태양전지 제조공정에서 열처리로 레이저를 사용하는 도핑공정은 태양전지의 성능을 결정짓는 중요한 요소이다. 그러나 퍼니스를 이용하는 공정에서는 선택적으로 고농도(Heavy) 도핑영역을 형성하기가 어렵다. 레이저를 사용한 선택적 도핑의 경우 고가의 레이저 장비가 요구되어지며, 레이저 도핑 후 고온의 에너지로 인한 웨이퍼의 구조적 손상 문제가 발생된다. 본 연구는 저가이면서 코로나 방전 구조의 대기압 플라즈마 소스를 제작하였고, 이를 통한 선택적 도핑에 관한 연구를 하였다. 대기압 플라즈마 제트는 Ar 가스를 주입하여 수십 kHz 주파수를 인가하여 플라즈마를 발생시키는 구조로 제작하였다. P-type 웨이퍼(Cz)에 인(P)이 shallow 도핑 된(120 Ohm/square) PSG (Phosphorus Silicate Glass)가 제거되지 않은 웨이퍼를 사용하였다. 대기압 플라즈마 도핑 공정 처리시간은 15 s와 30 s이며, 플라즈마 전류는 40 mA와 70 mA로 처리하였다. 웨이퍼의 도핑프로파일은 SIMS (Secondary Ion Mass Spectroscopy)측정을 통하여 분석하였으며, 도핑프로파일로 전기적 특성인 면저항(sheet resistance)을 파악하였다. 도펀트로 사용된 PSG에 대기압 플라즈마 제트로 도핑공정을 처리한 결과 전류와 플라즈마 처리시간이 증가됨에 따라 도핑깊이가 깊어지고, 면저항이 향상하였다. 대기압 플라즈마 도핑 후 웨이퍼의 표면구조 손상파악을 위한 SEM (Scanning Electron Microscopy) 측정결과 도핑 전과 후 웨이퍼의 표면구조는 차이가 없음을 확인하였으며, 대기압 플라즈마 도핑 폭도 전류와 플라즈마 처리시간이 증가됨에 따라 증가하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제19권2호
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• pp.170-178
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• 2015

이 연구에서는 산업부산물인 알카리활성 슬래그와 알칼리 활성화제 (물유리, 수산화나트륨)에 강섬유를 사용하였으며, 이를 철근콘크리트 보에 적용하여 휨성능 평가를 하였다. 주요변수는 알칼리 활성화제의 혼입비율 및 강섬유를 혼입으로 총 8개의 실험체를 제작하였으며, 재료 및 구조성능 평가를 위한 실험을 수행한 결과 다음과 같은 결론을 얻었다. 친환경 알카리활성 슬래그 섬유보강콘크리트를 사용한 철근콘크리트 보는 전반적으로 휨 또는 휨-전단에 의하여 파괴되었다. 그리고 수산화나트륨의 몰 증가와 강섬유를 보강한 결과 최대내력이 15.8~25.9% 증가한 값이 나타났으며, 연성 또한 높게 나타났다. 친환경 알카리활성 슬래그 섬유보강콘크리트는 기존의 콘크리트를 대체할 수 있는 기초연구로서 향후 건설소재 및 재료분야에 활용할 수 있을 것으로 사료되며, 이러한 특성을 바탕으로 콘크리트 2차 제품 생산과 구조부재를 PC화하여 활용할 경우 생산성 향상, 공기단축 등 효율이 상승될 것으로 보인다.