• Korean Journal of Materials Research
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• v.6 no.4
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• pp.379-387
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• 1996

본 연구에서는 GaAs 소자제작 및 epi-layer 성장 공정에 있어 이용되어지는 HCI, H3PO4, 탈이온수(de-ionized water:DIW)를 통한 습식제정후 공기중 노출에 따른 오염을 최소화하여 표면상태 변화를 진성적(intrinsic)으로 관찰하고자 모든 세정처리를 아르곤 가스(argon gas)로 분위기가 유지되는 glove box에서 수행하였으며, 표면조성 및 결합상태 변화에 대한 관찰은 X-선 광전자 분광기(X-ray photoelectron spectroscopy)를 통해 이루어졌다. 고진공하에서 GaAs를 벽개하여 관찰함으로써 Ga이 대기중 산소이온과 우선적으로 결합함을 알 수 있었고, 이런 GaAs 표면의 반응성에 대한 고찰을 바탕으로 습식세정에 따른 화학반응 기구가 제시 되어졌다. HCI 및 H3PO4/DIW/HCI처리후 CI-이온의 Ga 이온과의 반응에 의한 Ga-CI결합의 형성과 As 산화물의 높은 용해도에 따른 As 산화물의 완전한 제거 및 식각전 초기(bare)GaAsvyaus에 존재하는 원소(elemental)As 상태의 식각후 잔류가 관찰되어졌다. 또 HCI, H3PO4/DIW/HCI 처리하고 DIW로 세척후 표면상태 변화를 관찰한 결과, DIW처리에 의해 elemental As 상태가 증가함을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.457-464
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• 2006

Controlled auto ignition (CAI) combustion, also known as HCCI (homogeneous charge compression ignition), offers the potential to simultaneously improve fuel economy and reduce emission. CAI-combustion was achieved in a single cylinder gasoline DI engine, with a cylinder running in a CAI mode. Standard components were used the camshafts which had been modified in order to restrict the gas exchange process. The effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region were investigated. The effect that injection timings on factor such as start of combustion, combustion duration and heat release rate was also investigated. From results early injection caused the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gave rise to good mixing of the fuel-air.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.465-471
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• 2006

Controlled auto-ignition(CAI) combustion, offers the potential to improve fuel economy and reduce emission simultaneously. In this study, CAI-combustion was achieved in a single cylinder gasoline DI engine with modified camshafts in order to restrict the gas exchange process. We investigated the effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region. The effect of injection timings on combustion characteristic such as start of combustion, combustion duration and heat release rate was also investigated. From the result early injection causes the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gives rise to good mixing of the fuel/air. On the other hand, late injection extended the operation region more than early injection but the emissions of HC and NOx were more or less increased than early injection.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.102-107
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• 2019

This paper proposes a method to improve the mass spectral detection performance of the residual gas analyzer. By improving the mode estimation method for setting the threshold value and improving the additive noise elimination method, it is possible to detect mass spectrums having low peak values of the threshold level difficult to distinguish from noise. Ion signal blocks for each mass index with noise removed by the improved method are effective for eliminating invalid ion signals based on the linear and quadratic fittings. The mass spectrum can be obtained from the quadratic fitted curves for the reconstructed ion signal block using only the valid ion signals. In addition, the resolution of the mass spectrum can be improved by correcting the error caused by the shift of the spectral peak position. To verify the performance of the proposed method, computer simulations were performed using real ion signals obtained from the residual gas analysis system under development. The simulation results show that the proposed method is valid.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.97-100
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• 2018

$NF_3$ Plasma etching of silicon was conducted by injecting only $NF_3$ gas into reactive ion etching. $NF_3$ Plasma etching was done in intermediate pressure. Silicon etching by $NF_3$ plasma in reactive ion etching was diagnosed through residual gas analyzer and optical emission spectroscopy. In plasma etching, optical emission spectroscopy is generally used to know what kinds of species in plasma. Also, residual gas analyzer is mainly to know the byproducts of etching process. Through experiments, the results of optical emission spectroscopy during silicon etching by $NF_3$ plasma was analyzed with connecting the results of etch rate of silicon and residual gas analyzer. It was confirmed that $NF_3$ plasma etching of silicon in reactive ion etching accords with the characteristic of reactive ion etching.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.108-115
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• 2019

The thermal response of elastomeric insulators used as protection against high-temperature and high-pressure combustion gases varies depending on their composition and thermal environment conditions. In this paper, the thermal response characteristics of elastomeric insulators in different mixing environments were compared. Tests to determine thermal protection performance were carried out using a thermal protection rubber evaluation motor(TPREM), combustion gas velocities of 20 m/s and 100 m/s were tested at a chamber pressure of 1,000 psig. The pressure time curve of the chamber, the temperature time curve of the internal materials, the residual thickness and the thermal destruction depth of the test specimens were obtained. The results showed that the thermal protection performance of elastomeric insulators in different mixing environments was similar.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.55-66
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• 2012

The practical way to minimize the greenhouse gas is to reduce the emission of carbon dioxide. For this reason, CCS(Carbon Capture and Storage) technology, which could reduce carbon dioxide emission, has risen as a realistic alternative in recent years. In addition, the researcher is recently working into ways of applying CCS technologies with deep saline aquifer. In this study, the evaluation model on the feasibility of $CO_2$ sequestration in the deep saline aquifer using ANN(Artificial Neural Network) was developed. In order to develop the efficiency-evaluation model, basic model was created in the deep saline aquifer and sensitivity analysis was performed for the aquifer characteristics by utilizing the commercial simulator of GEM. Based on the sensitivity analysis, the factors and ranges affecting $CO_2$ sequestration in the deep saline aquifer were chosen. The result from ANN training scenario were confirmed $CO_2$ sequestration by solubility trapping and residual trapping mechanism. The result from ANN model evaluation indicated there is the increase of correlation coefficient up to 0.99. It has been confirmed that the developed model can be utilized in feasibility of $CO_2$ sequestration at deep saline aquifer.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.367-370
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• 2003

This study was carried out to investigate the possibility for reuse of solid organic wastes such as saccharified newspapers and boxes by two-phase anaerobic fermentation system. When 15g of newspaper and box wastes were digested for 24 days by batch fermentation, tCOD removal rate were found to be 60.9 and 62.4%, respectively. During this period, the amounts of biogas produced were 6.95 and 6.43L. The removal efficiencies of total solid were 34.8 and 33.4%, and those of volatile solid were 40.0 and 39.2%, respectively. That pH was around 7.5 after 20-days operation means methane fermentation is well advanced. In case of semicontinuous reaction, tCOD removal efficiencies of newspaper and box wastes were 64.7 and 65.0%, respectively for 14-days operation. It has been shown that each of the average biogas amounts produced after 25 days operation (stabilization stage for methane fermentation) was 0.31 and 0.30L/g dry wt./day, respectively, and each methane contents was 57.3 and 56.2%, respectively. After the reaction continued for 25 days, pHs in the anaerobic acidogenic and methanogenic fermenters were shown to be 5.0 and 7.5, respectively.

• The Journal of the Petrological Society of Korea
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• v.17 no.3
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• pp.179-190
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• 2008

The distribution characteristics of some major environmental radionuclides ($^{40}K$, $^{228}Ac$, $^{226}Ra$, $^{222}Rn$) and U in rocks, soils and soil gas were studied at Geumjeong-Gu, Busan, Korea. The activities of radionuclides in granitic rocks are decreased in the odor of $^{40}K$>thorium decay series>uranium decay series. This reveals that Th was relatively more enriched in granitic rocks than U. The U content and activity of $^{226}Ra$ and $^{228}Ac$, however, don't reflect the fractionation sequence of granitic rocks in the study area. The activities of all these radionuclides and U content in soils are generally higher than in rocks, and their distribution in rocks, soils and soil gas show very low co-relationship. These facts indicate that the activities of radionuclides in soil and soil gas were greatly affected by leaching and adsorption properties of the radionuclides and their parents during weathering and pedogenetic process rather than their concentrations in parent rocks.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.78-78
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• 2000

다결정 실리콘-게르마늄 (poly-SiGe)은 태양전지 개발에 있어서 중요한 물질이다. 우리는 소량의 Ge(x=0.05)으로부터 다량의 Ge(x=0.67)을 함유한 수소화된 비정질 실리콘-게르마늄 (a-SiGe:H) 박막의 고상결정화 과정을 ESR (electron spin resonance)방법으로 조사해보았다. 먼저 PECVD 방법으로 Corning 1737 glass 위에 a-Si1-xGex:H 박막을 증착시켰다. 증착가스는 SiH4, GeH4 가스를 썼으며, 기판온도는 20$0^{\circ}C$, r.f. 전력은 3W, 증착시 가스압력은 0.6 Torr 정도이었다. 증착된 a-SiGe:H 박막은 $600^{\circ}C$ N2 분위기에서 다시 가열되어 고상결정화 되었고, 결정화 정도는 XRD (111) peak의 세기로부터 구해졌다. ESR 측정은 상온 x-band 영역에서 수행되었다. 측정된 ESR스팩트럼은 두 개의 Gaussian 함수로써 Si dangling-bond와 Ge dangling-bond 신호로 분리되었다. 가열 초기의 a-SiGe:H 박막 결함들의 스핀밀도의 증가는 수소 이탈에 기인하고, 또 고상결정화 과정에서 결정화된 정도와 Ge-db 스핀밀도의 변화는 서로 깊은 상관관계가 있음을 알 수 있었다. 특히 Ge 함유량이 큰 박막 (x=0.21, 0.67)에서 뿐만 아니라 소량의 Ge이 함유된 박막(x=0.05)에서도 Ge dangling-bond가 Si dangliong-bond 보다 고상결정화 과정에서 더 중요한 역할을 한다는 것을 알수 있었다. 또한 초기 열처리시 Si-H, Ge-H 결합에서 H의 이탈로 인하여 나타나는 Si-dangling bond, Ge-dangling bond 스핀밀도의 최대 증가 시간은 x 값에 의존하였는데 이러한 결과는 x값에 의존하는 Si-H, Ge-H 해리에너리지로 설명되어 질 수 있다. 층의 두께가 500 미만인 커패시터의 경우에 TiN과 Si3N4 의 계면에서 형성되는 슬릿형 공동(slit-like void)에 의해 커패시터의 유전특성이 파괴된다는 사실을 알게 되었으며, 이러한 슬릿형 공동은 제조 공정 중 재료에 따른 열팽창 계수와 탄성 계수 등의 차이에 의해 형성된 잔류응력 상태가 유전막을 기준으로 압축응력에서 인장 응력으로 바뀌는 분포에 기인하였다는 사실을 확인하였다.SiO2 막을 약화시켜 절연막의 두께가 두꺼워졌음에도 기존의 SiO2 절연막의 절연 파괴 전압 및 누설 전류오 비교되는 특성을 가졌다. 이중막을 구성하고 있는 안티퓨즈의 ON-저항이 단일막과 비교해 비슷한 것을 볼 수 잇는데, 그 이유는 TiO2에 포함된 Ti가 필라멘트에 포함되어 있어 필라멘트의 저항을 감소시켰기 때문으로 사료된다. 결국 이중막을 구성시 ON-저항 증가에 의한 속도 저하 요인은 없다고 할 수 있다. 5V의 절연파괴 시간을 측정한느 TDDB 테스트 결과 1.1$\times$103 year로 기대수치인 수십 년보다 높아 제안된 안티퓨즈의 신뢰성을 확보 할 수 있었다. 제안된 안티퓨즈의 이중 절연막의 두께는 250 이고 프로그래밍 전압은 9.0V이고, 약 65$\Omega$의 on 저항을 얻을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품 개발에 따른 새로운 수요 창출과 수익률 향상, 기존의 기능성 안료를 나노(nano)화하여 나노 입자를 제조, 기존의 기능성 안료에 대한 비용 절감 효과등을 유도 할 수 있다. 역시 기술적인 측면에서도 특수소재 개발에 있어 최적의 나노 입자 제어기술 개발 및 나노입자를 기능성 소재로 사용하여 새로운 제품의 제조와 고압 기상 분사기술의 최적화에 의한 기능성 나노 입자 제조 기술을 확립하고 2차 오염 발생원인 유기계 항균제를 무기계 항균제로 대체할 수 있다. 이와 더불