• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.4
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• pp.49-61
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• 1981

A generally applicable computer simulation program for diffused silicon solar cells has been developed on the basis of the experimental results. The program can be easily used to obtain the spectral response and I-V characteristics for N+P, P+N N+PP+, P+NN+cells by changing various input parameters. The insolated spectra can be taken from AMI and constant intensity and GE - ELH lamp light sources. The options for AR coating are Si3N4 film and materials with constant reflectance including zero reflectance for ideal case. The computer simulation demonstrates successful results compared with the measured values for the short circuit current, open circuit voltage, efficiency, spectral response, quantum efficiency, I-V characteristics, etc. This program was used to optimize doping concentration, cell thickness, light concentration, junction depth, and to obtain the limit values for front surface recornbination velocity, effective carrier life time in the depletion regions and shunt resistance, and also to drive the changing rate in conversion efficiency depending on operation temperature, series resistance and electric field strength in N+P+ bulk regions.

• Journal of the Korean Vacuum Society
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• v.13 no.1
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• pp.22-28
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• 2004

Ta films were deposited on Si (100) substrates at zero substrate bias voltage and a substrate bias voltage of -125 V ($V_{s}$ = -125 V) using a non-mass separated ion beam deposition system. To investigate the effect of the negative substrate bias voltage on the impurity concentration in the Ta films, secondary ion mass spectrometry (SIMS) was used to determine impurities in the Ta films. By the SIMS depth profiles with $Cs^{+}$ cluster ion beam, high intensities of O, C and Si were clearly found in the Ta film at $V_{s}$ = 0 V, whereas these impurities remarkably decreased in the Ta film at $V_{s}$ = -125 V. Furthermore, from the SIMS result with $Cs^{+}$ and $O_2^{+}$ ion beams, it was found that applying the negative substrate bias voltage could affect individual impurity contents in the Ta films during the deposition. Discussions concerning the effect of the negative substrate bias voltage on the impurity concentration of Ta films will be described in details.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.59-65
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• 1999

In this paper, we had studied the possibility of application as Cu thin films from (hfac)Cu(VTMOS) which is very stable. Cu thin films had been studied as a function of deposition temperature. Substrates used in the experiment were PVD TiN on Si wafer. Deposition conditions were as follow : deposition temperature $50^{\circ}C$. Cu thin films were analyzed by AES, four point probe, XRD and SEM. All of deposited films were very pure and some favoring of <111> planes perpendicular to the substrate surface were observed. Cu thin films had two distinct growth rates at various deposition temperature. One is the surface reaction limited region below $200^{\circ}C$, and the other is the mass transport limited region above $200^{\circ}C$. The resistivity of deposited Cu thin films under the optimum deposition condition is $2.5mu\Omega.cm$ Thus, properties of deposited Cu thin films using (hfac)Cu(VTMOS) didn't show difference with Cu thin films from other precursors.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.35-43
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• 2003

In this study, the physical and chemical characteristics of incinerated pulp and sewage sludge ashes for recycling and reuse were examined. Then we studied the application to the cement admixture by pozzolanic reaction. The particle size of incinerated pulp and sewage sludge ashes was distributed around $10{\sim}100{\mu}$, and the contents of $SiO_2$ and $Al_2O_3$ were 45.8~51.0%, respectively. Compressive strengths of the solidified ashes were relatively higher, when the content of substituted incineration ashes was 10% and the porosity was also lower except for the case of sewage sludge ash. As results, it is shown that it may be possible to recycle incinerated pulp sludge ashes as cement admixtures.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.2
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• pp.31-48
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• 2014

This study is carried out to offer the raw data for conservation and management of tidal flat ecosystem by surveying and analysing the flora distributed in Daesong tidal flat wetland, Ahnsan-si, Gyeonggi-do coast, Korea. The results of surveying the flora were recorded as 186 taxa including 45 families, 121 genera, 170 species, 14 varieties and 2 forms. The halophytes checked around this site were 20 taxa including Atriplex gmelinii, Salicornia europaea, Suaeda glauca, Suaeda japonica, Phragmites communis, Carex scabrifolia and so forth. Polygonum bellardii that species had ecological value was the specific plant by floristic region. The growth locations of halophytes were 11 taxa of upper, 4 taxa of high tide line and 5 taxa of lower. The naturalized plants were 42 taxa including Phytolacca americana, Chenopodium glaucum, Melilotus alba, Veronica persica, Bidens pilosa, Leptochloa fusca and so forth. Because Aster subulatusand Leptochloa fusca grew a upper tidal flat wetland, they had the characteristics of halophytes. The focuses on the management of Daesong wetland were halophytes and naturalized plants. Firstly, to maintain a halophytes communities, we will sow the halophytes seeds and plant the individuals. And In-Situ conservation was applied to Polygonum bellardii habitat. Secondly, to prevent the genesis of naturalized plant, we will don't disturb around the wetland environment. The invasive alien plant, Lactuca scariola, was removed by periodic monitoring and purification activity.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.26-31
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• 2005

The strong continuous fiber reinforced metal matrix composites (MMCs) are recently used in aerospace and transportation applications as an advanced material due to its high strength and light weight. Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In order to be able to utilize these MMCs effectively and with safety, it must be determined their elastic plastic behaviors at the interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interlace was treated as three thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. Using proposed model, the effects of the interface region and fiber arrangement in MMCs on the distributions of stress and strain are evaluated. The stress distributions of a thin multi layer interface have much less changes compared with conventional perfect interface. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.93-101
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• 1992

Several "Napseok" mines are distribute in the Miryang area where the volcanic rocks are hydrothermally altered. The "Napseok" are pyrophyllite and dickite, with a small amount of silicates such as quartz, illite, tosudite and dumortierite. Other associated minerals are oxides, hydroxides, sulfides, sulfates and phosphates. Pyrophyllite which occurs as 2M polytype exhibits that the basal spacing increases due to dehydroxylation at 750${\circ}C$. Halloysite shows tubular forms. Wavellite is precipitated in fissures during the latest stage of the hydrothermal alteration process. Five mineral zones, that is pyrophyllite-deckite, illite, halloysite, silica, and albite-chlorite zones, are recognized with decreasing alteration degree. Clay minerals were formed by leaching of Si and alkali ions fron the country rocks, considering mineral assemblages, pyrophyllite polytype and thermodynamical data reported in the literature, temperatures of formation of main clay deposits are assumed to be 270 to 350${\circ}C$.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.647-653
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• 2007

In ready mixed concrete factory, in case of using the high molecular additive in winter especially the liquid additive for the early strength, it is required to check the stability. In this research, the freezing and gelling characteristics of the liquid additive for the early strength is reviewed, the material and mechanical solution are proposed to that the practical quality control method will be suggested. As the result, the Freezing temperature of the liquid additive for the early strength is $-11.8^{\circ}C$, and it is the lower than the temperature at which the strength is shown. By making with sodium silicate of $37{\pm}0.5%$ designed by $SiO_2\;and\;Na_2O$ in 0.31 of mol ratio, it minimizes the gelling at the lower temperature. On the other hand, facilities for storing and supplying the material should be set at $40^{\circ}C$ so the temperature distribution is well spreaded for practical operation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.507-507
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• 2013

유리기판으로 투과되는 빛들 중에는 내부 전반사나 wave-guided mode로 인하여 손실이 일어나 일반적으로 20%의 광추출 효율을 가진다. 이러한 문제점을 해결하기 위한 연구에는 Photonic Crystal과 같은 주기적인 나노 구조물이 있는데 이러한 구조물을 제작하기 위한 마스크 공정 과정은 대부분 복잡하거나 비싼 단점이 있다. 이에 본 발표에서는 마스크 없이 비정질소다라임 유리의 구조물 생성으로 광 추출 효율이 상승하는지 보고자 하였다. M-ICP (Magnetized-Induced Coupled Plasma)란 용량 결합형 플라즈마와 유도 결합형 플라즈마 두 가지 방식의 플라즈마를 이용한 것인데 용량 결합형 플라즈마를 이용해 이온이 sheath에 의해 가속되어 유리표면에 부딪히고 그에 따라 유리가 식각되는 물리적 식각을 이용하였다. 또한 이온의 밀도를 조절하기 위해 유도결합형 플라즈마 방식을 이용하여 식각률을 높였다. 화학적 식각을 위해서는 CF4와 O2혼합 가스를 이용해 F가 Si와 결합하여 SiF4가 되어 사라지고 탄소잔여물인 C는 O2와 반응하여 제거하였다. 그 결과, 랜덤한 분포를 가지는 미세한 구조물(stochastic sub-wavelength structure)을 유리 표면에 형성할 수 있었고, 또한 다양한 가스 종류와 압력, source power와 bias power, 그리고 시간을 바꿔가며 미세 구조물들을 관찰하였다. 실험 결과, 가시광선 파장 이하의 높이를 갖고 수 마이크로미터의 너비를 갖는 구조물이 전반사되는 빛을 효율적으로 추출하는 것을 산란되는 빛의 정도인 diffusive transmittance 가 기존 0%에서 15% 정도로 증가하는 것으로 스펙트로포토미터 측정을 통해 확인하였다. 이러한 유리 기판 위 구조물 생성방법을 OLED에 적용한다면 적은 비용으로 소자의 효율을 크게 향상 시킬 수 있을 것이다. 또한 본 처리 과정의 장점은 기존의 방법에 필요한 스퍼터링이나 RTA 처리 과정이 필요 없어 공정 단가 절감과 제조 공정의 단순화로 높은 생산성을 얻을 수 있으며 대면적화에도 유리하다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.482-482
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• 2013

반도체 소자의 미세화와 더불어 세정공정의 중요성이 차지하는 비중이 점점 커지고, 이에 따라 세정 기술 개발에 대한 요구가 증대되고 있다. 기존 세정 기술은 화학약품 위주의 습식 세정 방식으로 표면 손상, 화학 반응, 부산물, 세정 효율 등 여러 가지 어려움이 있다. 따라서 건식세정 방식이 활발하게 도입되고 있으며 대표적인 것이 에어로졸 세정이다. 에어로졸 세정은 기체상의 작동기체를 이용하여 에어로졸을 형성하고 표면 오염물질과 직접 물리적 충돌을 함으로써 세정한다. 하지만 이 또한 생성되는 에어로졸 내 발생 입자로 인해 패턴 손상이 발생하며 이러한 문제점을 극복하기 위하여 본 연구에서는 가스클러스터 장치를 이용한 세정 특성 평가에 관한 연구를 수행하였다. 가스 클러스터란 작동기체의 분자가 수십에서 수백 개 뭉쳐 있는 형태를 뜻하며 이렇게 형성된 클러스터는 수 nm 크기를 형성하게 된다. 그리고 짧은 시간의 응축에 의해 수십 nm 크기까지 성장하게 된다. 에어로졸 세정과 다르게 클러스터가 성장할 환경과 시간을 형성하지 않음으로써 작은 클러스터를 형성하게 되며 이로 인해 패턴 손상을 최소화 하고 상대적으로 높은 효율로 오염입자를 제거하게 된다. 클러스터 세정 장비를 이용한 표면 처리는 충돌에 의한 제거에 기반한다. 따라서 생성 및 가속되는 클러스터로부터 대상으로 전달되는 운동량의 정도가 세정 특성에 영향을 미치며 이는 생성되는 클러스터의 크기에 종속적이다. 생성 클러스터의 크기 분포는 분사 거리, 유량, 분사 각도, 노즐 냉각 온도 등의 변수에 관한 함수이다. 따라서 본 연구에서는 $CO_2$ 클러스터를 이용한 세정 특성을 평가하기 위하여 이러한 변수에 따라서 오염 입자의 종류, 크기에 따른 PRE (particle removal efficiency)를 평가하고 다양한 선폭의 패턴을 이용하여 손상 실험을 수행하였다. 제거 효율에 사용된 입자는 $CeO_2$와 $SiO_2$이며, 각각 30, 50, 100, 300 nm 크기를 정량적으로 오염시킨 쿠폰 웨이퍼를 제조하여 세정 효율을 평가하였다. 정량적 오염에는 SMPS (scanning mobility particle sizer)를 이용한 크기 분류와 정전기적 입자 부착 시스템이 사용되었다. 또한 패턴 붕괴 평가에는 35~180 nm 선폭을 가지는 Poly-Si 패턴을 이용하였다. 실험 결과 클러스터 형성 조건에 따라 상대적으로 낮은 패턴 붕괴에서 95% 이상의 높은 오염입자 제거효율을 전반적으로 보이는 것을 확인할 수 있었다. 따라서 이론적 계산에 기반하여 세정에 요구되는 클러스터 크기를 가정하고, 이를 통하여 세정에 적용할 경우 높은 기존 세정 방법의 단점을 보완하면서 높은 세정 효율을 가지는 대체 세정 방안으로 이용할 수 있음을 확인하였다.