• Korean Chemical Engineering Research
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• 제46권3호
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• pp.619-625
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• 2008

패시베이션 및 절연 목적으로 이용하는 플라즈마 화학기상증착(PECVD)법에 의해 증착된 무기막과 웨이퍼 간 본딩 접착제로 이용하는 유기 박막 적층면의, 열 순환에 의한 잔류 응력 및 본딩 결합력의 효과를 4점 굽힙 시험법과 웨이퍼 곡률 측정법에 의해 평가하였다. 무기막으로는 산화 규소막($SiO_2$)과 산화 질화막($SiN_x$)이, 유기 박막으로는 BCB(Benzocyclobutene)가 이용되었다. 이를 통해, 열 순환 동안 무기막과 유기막 사이에서의 잔류 응력과 본딩 결합력의 상관관계에 대한 모델식을 개발하였다. 최대 온도 350 및 $400^{\circ}C$에서 수행한 열 순환 공정에서, PECVD 산화 질화막과 BCB로 구성된 다층막에서, 본딩 결합력은 첫 번째 순환 공정 동안 감소한다. 이는 산화질화막 내 잔류인장응력의 증가가 다층막의 잔류응력에 의해 변형되는 에너지 및 본딩 결합력의 감소를 유도한다는 모델식의 예측과 일치하며, PECVD 산화 규소막내 잔류 압축 응력의 감소가 다층막의 잔류응력에 의해 변형되는 에너지 및 본딩 결합력 상승을 이끄는 산화 규소막과 BCB 구조의 본딩 결합력 결과와 비교된다. 이러한 산화 규소막과 산화 질화막을 포함한 다층막의 상반된 본딩 결합력은 증착 공정 후 막 내에 형성된 수소 결합이 고온 순환 공정 동안 축합 반응을 통해 더 밀집되어 인장응력을 형성하기 때문임을 알 수 있었다.

• 한국광물학회지
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• 제22권2호
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• pp.163-176
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• 2009

진해지역에 위치하는 납석광상에 대하여, 광산 지질조사를 통해 산출상태를 파악하고, X-선회절분석, X-선형광분석, 전자현미분석, ICP분석 등을 통하여 변질광물의 광물학적 특성을 조사하였다. 그 결과, 이 납석광상에는 일라이트, 딕카이트, 엽납석, 다이어스포어, 녹니석, 황철석, 침철석 등의 다양한 광물들이 산출되었다. 이들 구성광물의 조합을 검토한 결과, A: 석영, B: 석영+ 일라이트, C: 석영 + 일라이트 + 딕카이트, D: 엽납석 + 일라이트 + 딕카이트 + 다이어스포어의 4개 광물조합으로 주로 구분되었다. 이들 광물조합의 산출상태로 보아 규화대, 일라이트변질대, 카올린변질대, 엽납석변질대로 구분할 수 있는 것으로 나타났다. 이 규화대의 대부분은 약 90% 이상의 높은 $SiO_2$ 함량을 보이고 작은 입자의 석영들로만 거의 구성되어 있는 특징을 보였다. 엽납석은 2M형의 폴리타이프에 해당되는 것으로 나타났다. 이 광상의 모암은 유문암질암, 안산암질 응회암 및 화산 각력암 등의 화산암이며, 모암의 차이에 따라 변질대 분포양상이 다소 다르게 나타났다. 이런 화산암이 수소이온 및 실리카의 활동도가 높은 산성열수용액에 의해 변질작용을 받아 납석광상이 형성되었으며, 그중에서 엽납석변질대가 가장 고온의 환경에서 생성된 것으로 사료된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.434-435
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• 2012

Plasma enhanced chemical vapor deposition (PECVD) silicon dioxide thin films have many applications in semiconductor manufacturing such as inter-level dielectric and gate dielectric metal oxide semiconductor field effect transistors (MOSFETs). Fundamental chemical reaction for the formation of SiO2 includes SiH4 and O2, but mixture of SiH4 and N2O is preferable because of lower hydrogen concentration in the deposited film [1]. It is also known that binding energy of N-N is higher than that of N-O, so the particle generation by molecular reaction can be reduced by reducing reactive nitrogen during the deposition process. However, nitrous oxide (N2O) gives rise to nitric oxide (NO) on reaction with oxygen atoms, which in turn reacts with ozone. NO became a greenhouse gas which is naturally occurred regulating of stratospheric ozone. In fact, it takes global warming effect about 300 times higher than carbon dioxide (CO2). Industries regard that N2O is inevitable for their device fabrication; however, it is worthwhile to develop a marginable nitrous oxide free process for university lab classes considering educational and environmental purpose. In this paper, we developed environmental friendly and material cost efficient SiO2 deposition process by substituting N2O with O2 targeting university hands-on laboratory course. Experiment was performed by two level statistical design of experiment (DOE) with three process parameters including RF power, susceptor temperature, and oxygen gas flow. Responses of interests to optimize the process were deposition rate, film uniformity, surface roughness, and electrical dielectric property. We observed some power like particle formation on wafer in some experiment, and we postulate that the thermal and electrical energy to dissociate gas molecule was relatively lower than other runs. However, we were able to find a marginable process region with less than 3% uniformity requirement in our process optimization goal. Surface roughness measured by atomic force microscopy (AFM) presented some evidence of the agglomeration of silane related particles, and the result was still satisfactory for the purpose of this research. This newly developed SiO2 deposition process is currently under verification with repeated experimental run on 4 inches wafer, and it will be adopted to Semiconductor Material and Process course offered in the Department of Electronic Engineering at Myongji University from spring semester in 2012.

• 한국재료학회지
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• 제9권11호
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• pp.1049-1054
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• 1999

근사단결정 다이아몬드막 성장시 입자의 정렬을 개선하기 위한 집합조직성장의 2단계 성장방법을 제안하였다. 메탄조성 4%, 기판온도 $850^{\circ}C$ 조건에서 (100) Si 기판에 - 200V 바이어스를 인가하여 20분동안 전처리 하였다. 처리한 기판을 2%[CH$_4$], 기판온도 $810^{\circ}C$에서 2~35시간동안 <100> 집합조직을 지니도록 1단계로 성장시켰다. 이 시편의 성장표면을 평탄화하기 위하여 (100) 면이 성장하도록 2% [CH$_4$], 기판온도 $850^{\circ}C$ 조건에서 2단계 성장시켰다. 1단계 성장시간에 따른 다이아몬드막의 배열정도를 {111} X-ray pole figure의 반가폭 변화를 통해 관찰하였다. 1단계 성장 후 입자정렬은 막의 두께가 증가할수록 개선되었다. 그러나 <100> 집합조직의 표면조직은 피라미드 형태의 굴곡을 피할 수 없었다. 2단계 성장시 (100) 면의 성장으로 인해 막의 표면은 평탄화되었으며, 이때 입자의 정렬은 1단계 성장시간에 크게 의존하였다.

• 천문학논총
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• 제30권2호
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• pp.559-563
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• 2015

Monitor of All-sky X-ray Image (MAXI) is a Japanese X-ray all-sky surveyer mounted on the International Space Station (ISS). It has been scanning the whole sky since 2009 during every 92-minute ISS rotation. X-ray transients are quickly found by the real-time nova-search program. As a result, MAXI has issued 133 Astronomer's Telegrams and 44 Gamma-ray burst Coordinated Networks so far. MAXI has discovered six new black holes (BH) in 4.5 years. Long-term behaviors of the MAXI BHs can be classified into two types by their outbursts; a fast-rise exponential-decay type and a fast-rise flat-top one. The slit camera is suitable for accumulating data over a long time. MAXI issued a 37-month catalog containing 500 sources above a ~0.6 mCrab detection limit at 4-10 keV in the region ${\mid}{b}{\mid}$ > $10^{\circ}$. The SSC instrument utilizing an X-ray CCD has detected diffuse soft X-rays extending over a large solid angle, such as the Cygnus super bubble. MAXI/SSC has also detcted a Ne emission line from the rapid soft X-ray nova MAXI J0158-744. The overall shapes of outbursts in Be X-ray binaries (BeXRB) are precisely observed with MAXI/GSC. BeXRB have two kinds of outbursts, a normal outburst and a giant one. The peak dates of the subsequent giant outbursts of A0535+26 repeated with a different period than the orbital one. The Be stellar disk is considered to either have a precession motion or a distorted shape. The long-term behaviors of low-mass X-ray binaries (LMXB) containing weakly magnetized neutron stars are investigated. Transient LMXBs (Aql X-1 and 4U 1608-52) repeated outbursts every 200-1000 days, which is understood by the limit-cycle of hydrogen ionization states in the outer accretion disk. A third state (very dim state) in Aql X-1 and 4U 1608-52 was interpreted as the propeller effect in the unified picture of LMXB. Cir X-1 is a peculiar source in the sense that its long-term behavior is not like typical LMXBs. The luminosity sometimes decreases suddenly at periastron. It might be explained by the stripping of the outer accretion disk by a clumpy stellar wind. MAXI observed 64 large flares from 22 active stars (RS CVns, dMe stars, Argol types, young stellar objects) over 4 years. The total energies are $10^{34}-10^{36}$ erg $s^{-1}$. Since MAXI can measure the spectrum (temperature and emission measure), we can estimate the size of the plasma and the magnetic fields. The size sometimes exceeds the size of the star. The magnetic field is in the range of 10-100 gauss, which is a typical value for solar flares.

• 한국환경보건학회지
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• 제44권1호
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• pp.55-62
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• 2018

Objectives: This study set out to measure the heavy metal concentrations in waste water produced in the casting pickling process at dental technical laboratories and examine the actual state of its treatment. Methods:The investigator measured the concentrations of each heavy metal at 55 dental technical laboratories using an inductively coupled plasma optical emission system. Results: The annual usage of electrolytes was under 10 L in 50 (90.9%), and was 10L or more in five (9.1%) laboratories. Among the laboratories, 15 (27.3%) commissioned the treatment of waste,12 (21.8%) treated the waste with general sewage,and 28 (50.9%) treated the waste in aseptic tank. The arithmetic $mean{\pm}standard$ deviation and the geometric mean of chrome(Cr) were $75.3{\pm}50.9$ and 58.3 mg/L; those of cobalt (Co) were $112.3{\pm}106.7$ and 66.1 mg/L; those of nickel (Ni) were $62.9{\pm}83.5$ and 8.9 mg/L; those of molybdenum (Mo) were $17.1{\pm}13.4$ and 12.0 mg/L; those of iron (Fe) were $31.5{\pm}44.1$ and 6.2 mg/L; those of lead (Pb) were $0.3{\pm}0.3$ and 0.3 mg/L; those of beryllium (Be) were $3.6{\pm}3.6$ and 2.0 mg/L. The hydrogen ion concentration was under pH 2 across all the samples. Conclusions: The findings show that the dental technical laboratories were not doing well with the separation, storage, collection, and treatment of the electrolytes they discarded, and that most of the electrolytes were introduced through the general sewage or aseptic tank. The causes of this include alack of perception among the practitioners at dental technical laboratories and contracted companies avoiding collection for economic reasons. There is a need for education to improve the perceptions of waste water treatment among the practitioners at dental technical laboratories. Environment-related departments should be stricter with legal applications in the central and local governments. It is also required to provide proper management of commissioned treatment.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.7-8
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• 2010

The surface conductive layer (SCL) of chemical vapor deposition (CVD) diamonds has attracting much interest. However, neither photoemission electron microscopic (PEEM) nor micro-spectroscopic (PEEMS) information is available so far. Since SCL retains in an ultra-high vacuum (UHV) condition, PEEM or PEEMS study will give an insight of SCL, which is the subject of the present study. The sample was made on a Ib-type HTHP diamond (001) substrate by non-doping CVD growthin a DC-plasma deposition chamber. The SCL properties of the sample in air were; a few tens K/Sq. in sheet resistance, ${\sim}180\;cm^2/vs$ in Hall mobility, ${\sim}2{\times}10^{12}/cm^2$ in carrier concentration. The root-square-mean surface roughness (Rq) of the sample was ~0.2nm as checked by AFM. A $2{\times}1$ LEED pattern and a sheet resistance of several hundreds K/Sq. in UHV were checked in a UHV chamber with an in-situ resist-meter [1]. The sample was then installed in a commercial PEEM/S apparatus (Omicron FOCUS IS-PEEM) which was composed of electro-static-lens optics together with an electron energy-analyzer. The presence of SCL was regularly monitored by measuring resistance between two electrodes (colloidal graphite) pasted on the two ends of sample surface. Figure 1 shows two PEEM images of a same area of the sample; a) is excited with a Hg-lamp and b) with a Xe-lamp. The maximum photon energy of the Hg-lamp is ~4.9 eV which is smaller that the band gap energy ($E_G=5.5\;eV$) of diamond and the maximum photon energy of the Xe-lamp is ~6.2 eV which is larger than $E_G$. The image that appear with the Hg-lamp can be due to photo-excitation to unoccupied states of the hydrogen-terminated negative electron affinity (NEA) diamond surface [2]. Secondary electron energy distribution of the white background of Figs.1a) and b) indeed shows that the whole surface is NEA except a large black dot on the upper center. However, Figs.1a) and 1b) show several features that are qualitatively different from each other. Some of the differences are the followings: the two main dark lines A and B in Fig.1b) are not at all obvious and the white lines B and C in Fig.1b) appear to be dark lines in Fig.1a). A PEEMS analysis of secondary electron energy distribution showed that all of the features A-D have negative electron affinity with marginal differences among them. These differences can be attributed to differences in the details of energy band bending underneath the surface present in SCL [3].

• 분석과학
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• 제24권4호
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• pp.243-248
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• 2011

루미놀 화학발광 시스템(luminol-$H_2O_2$)을 이용하여 수용액 중의 수은(II) 이온을 선택적으로 정량분석 하였다. 루미놀과 과산화수소의 반응에서 촉매작용을 하는 구리(II), 철(III), 크롬(III) 이온 등 다양한 금속이온의 농도를 정량분석한 연구결과가 보고되어 있다. 본 연구에서는 수은(II) 이온이 루미놀과 과산화수소의 반응에서 다른 금속이온과 같이 촉매작용을 하는 것을 관찰하였으며, 수용액 중 수은(II) 이온의 정량분석 조건을 최적화하기 위하여 반응시간, pH등에 따른 영향을 조사하였다. 또한 수은이온이 갖는 1가와 2가 산화수 중에서 수은(I) 이온은 루미놀과 과산화수소의 반응에 있어서 촉매작용을 하지 않았을 뿐만 아니라 반응에 어떠한 영향도 미치지 않았다. 또한 수은(I)과 수은(II) 이온이 공존하는 수용액 중의 수은(II) 이온의 분석과정에서 수은(I) 이온의 방해 효과는 관찰되지 않았다. 이를 바탕으로 하여 루미놀 화학발광 시스템을 이용하여 수용액 중의 수은(II) 이온만 선택적으로 분석하는 것이 가능하다는 결과와 함께 화학발광분석법과 ICP분석법으로부터 얻은 실험결과를 비교하여 수용액 내에 존재하는 수은 이온의 산화수별 농도를 확인할 수 있다. 루미놀 화학발광 시스템의 최적 분석조건 하에서, 수용액 중의 선택적 수은(II) 이온의 정량분석을 위해 얻은 검정곡선에서 직선성이 성립하는 농도범위는 $1.25{\times}10^{-5}{\sim}2.50{\times}10^{-3}M$이며, 이때 상관계수는 0.991이고, 검출한계는 $1.25{\times}10^{-7}M$이었다.

• 한국균학회지
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• 제44권1호
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• pp.23-30
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• 2016

본 연구에서는 복령의 성장 환경조건이 다른 지역(강원도, 경상도, 전라도)별 복령의 성분 분석 및 생리활성 비교를 위해 연구하였다. 일반성분 분석 결과, oxygen 46~48%로 가장 많이 포함하고 있었고 다음으로 38~39%의 Carbon, 6.05~6.1% Hydrogen, 0.17~0.21% Nitrogen으로 나타났다. 그리고 3개도 복령 모두에서 sulphur 성분은 발견되지 않았다. 지역별 복령을 inductively coupled plasma-mass spectrometry(ICP) 분석으로 11종의 무기질을 분석한 결과 S는 145~149 ppm, Mg은 69~72 ppm, P는 122~154 ppm로 비슷한 함유량을 나타냈고, Ca은 경상도(509.98 ppm)가 강원도(210.61 ppm)와 전라도 (223.88 ppm)보다 약 2~2.35배보다 많이 함유하였다. GC-MS 분석 결과 모든 복령에서 oleic aid 계열의 지방산이 확인되었다. 50% 에탄올 복령 추출물의 DPPH와 ABTS radical 소거활성과 FRAP 방법을 실행하여 항산화 효과를 알아보았다. 복령 추출물 10mg/ml의 농도에서 강원도, 전라도 복령의 DPPH와 ABTS의 $IC_{50}$ 값은 강원도(3 mg/mL), 경상도(23.03 mg/mL), 전라도(4.16 mg/mL)와 강원도(3.52 mg/mL), 경상도(12.17 mg/mL), 전라도(7.40 mg/mL)로 계산되었다. FRAP에서 $IC_{50}$ 값은 강원도(6.59 mg/mL), 경상도(19.06 mg/mL), 전라도(18.97 mg/mL)로 계산되었다. 연구에 사용한 복령의 항산화 활성은 농도 의존적인 증가를 보였으며 강원도, 전라도, 경상도 복령의 순으로 항산화 활성이 나타났다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.107-108
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• 2008

The spectacular development of AMLCDs, been made possible by a-Si:H technology, still faces two major drawbacks due to the intrinsic structure of a-Si:H, namely a low mobility and most important a shift of the transfer characteristics of the TFTs when submitted to bias stress. This has lead to strong research in the crystallization of a-Si:H films by laser and furnace annealing to produce polycrystalline silicon TFTs. While these devices show improved mobility and stability, they suffer from uniformity over large areas and increased cost. In the last decade we have focused on microcrystalline silicon (${\mu}c$-Si:H) for bottom gate TFTs, which can hopefully meet all the requirements for mass production of large area AMOLED displays [1,2]. In this presentation we will focus on the transfer of a deposition process based on the use of $SiF_4$-Ar-$H_2$ mixtures from a small area research laboratory reactor into an industrial gen 1 AKT reactor. We will first discuss on the optimization of the process conditions leading to fully crystallized films without any amorphous incubation layer, suitable for bottom gate TFTS, as well as on the use of plasma diagnostics to increase the deposition rate up to 0.5 nm/s [3]. The use of silicon nanocrystals appears as an elegant way to circumvent the opposite requirements of a high deposition rate and a fully crystallized interface [4]. The optimized process conditions are transferred to large area substrates in an industrial environment, on which some process adjustment was required to reproduce the material properties achieved in the laboratory scale reactor. For optimized process conditions, the homogeneity of the optical and electronic properties of the ${\mu}c$-Si:H films deposited on $300{\times}400\;mm$ substrates was checked by a set of complementary techniques. Spectroscopic ellipsometry, Raman spectroscopy, dark conductivity, time resolved microwave conductivity and hydrogen evolution measurements allowed demonstrating an excellent homogeneity in the structure and transport properties of the films. On the basis of these results, optimized process conditions were applied to TFTs, for which both bottom gate and top gate structures were studied aiming to achieve characteristics suitable for driving AMOLED displays. Results on the homogeneity of the TFT characteristics over the large area substrates and stability will be presented, as well as their application as a backplane for an AMOLED display.