• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.136.1-136.1
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• 2010

고체산화물 연료전지(SOFC)에서 사용되는 연결재의 주 기능은 각 단위 셀의 연료극과 다음 셀의 공기극을 전기적으로 연결하여, 공기와 사용연료의 분리역할을 하기위해 사용된다. SOFC용 연결재는 다른 구성요소 소재보다 높은 전기전도성, 낮은 이온전도성이 요구되며 SOFC는 고온에서 작동되기 때문에 다른 구성 소재들과 유사한 열팽창계수와 물리, 화학적인 안정성이 요구된다. 현재 연결재 제조기술은 plasma coating, sputtering, screen printing, 전사법등 다양한 연구가 진행되고 있다. 본 연구에서는 저렴한 비용으로 대량생산이 용이한 고상반응법을 적용하여 세라믹연결재를 제조하고, 그 특성을 연구하였다. 세라믹 연결재로서 선정한 합성조성은 $(La_{0.7}Ca_{0.3})(Cr_{0.9}Co_{0.1})O_3$로 SOFC 작동온도에서 높은 전기전도도를 나타낸다. LCCO 연결재를 1300, 1400 및 $1500^{\circ}C$에서 합성을 진행하였을 때 출발원료로 $CaCO_3$를 $CaF_2$로 대체하였을 때의 소결특성을 평가하였고, SEM과 XRD분석을 통하여 균질하고 결정성이 우수한 분말이 합성된 것을 확인하였고 DC impedance analyzer를 사용하여 전기전도도를 측정하였다. TMA를 사용하여 열팽창계수를 측정한 결과 YSZ(${\sim}10.8{\times}10^{-6}/^{\circ}C$)와 동일한 값을 나타내었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.176-176
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• 2012

본 연구는 GaN 기반의 전자소자의 표면 패시베이션 방법으로 열산화 공정을 이용한 알루미늄산화막 패시베이션 공정에 대하여 연구하였다. 결정질의 알루미늄산화물은 경도가 크고 화학적으로 안정적이기 때문에 외부 오염에 대한 소자 표면을 효과적으로 보호할 수 있으며, 열적안정성이 뛰어나 공정중 또는 공정 후의 고온 환경에서의 열 손상이 적은 장점을 가진다. 결정질 알루미늄산화막($Al_2O_3$)을 소자 표면에 형성하기 위해서 일반적으로 TMA (trimethlyaluminium)와 오존($O_3$)가스를 이용한 ALD 공정법이 사용되고 있으나 공정 비용이 비싸고 열산화막에 비해 전자 trapping이 많이 발생하여 전자이동도가 저하되는 단점이 있어, 본 연구에서는 열산화 공정을 이용하여 소자의 전기적 특성 저하를 발생시키지 않는 알루미늄산화막 패시베이션을 수행하였다. 실험에 사용된 기판은 AlGaN/GaN 이종접합 구조가 증착된 HEMT 제작용 기판을 사용하였으며 TLM 구조를 제작하여 소자의 채널 면저항 및 절연영역간 누설전류 특성을 확인하였다. TLM 구조가 제작된 샘플 위에 알루미늄을 100 ${\AA}$ 두께로 소자위에 증착하고 $O_2$ 분위기에서 약 $525{\sim}675^{\circ}C$ 온도로 3분간 열처리하여 알루미늄 산화막을 형성한 후 $950^{\circ}C$ 온도로 $N_2$ 분위기에서 30초간 안정화열처리 하여 안정한 알루미늄 산화막 패시베이션을 형성하였다. 알루미늄산화막 패시베이션 후 소자의 절연영역 사이의 누설전류는 패시베이션 전과 비슷한 크기를 나타냈고 패시베이션 후 채널의 면저항이 패시베이션 전에 비해 약 20% 감소한 것을 확인하였다. 또한 패시베이션된 소자와 패시베이션되지않은 소자에 대해 $900^{\circ}C$ 온도로 30초간 열처리한 결과 패시베이션 되지 않은 소자는 74%만큼 채널 면저항이 증가하였으며, 절연영역 누설전류가 다섯오더 크기로 증가한 반면 알루미늄산화막 패시베이션한 소자는 단지 13%의 채널 면저항의 증가를 나타내었고 절연영역 누설전류는 100배 감소한 값을 보여 알루미늄산화막 패시베이션이 소자의 열적 안정성을 향상시키는 것을 확인하였다.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.19
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• pp.8161-8169
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• 2014

Background: Cancer stem cells (CSC) are populations of cells responsible for tumor initiation, progression and therapeutic resistance in many cancers. In the present study, we aimed to investigate the expression pattern and clinical significance of two CSC markers, CD133 and Nestin, in a series of skin tumors. Materials and Methods: One hundred and thirteen paraffin blocks from skin cancers including 16 (14%) cases of melanoma, 37 (33%) of squamous cell cancer (SCC) and 60 (53%) of basal cell cancer (BCC) were collected and assembled in a tissue microarray (TMA). The samples were immunohistochemically examined for the expression of CD133 and Nestin. Expression of these markers was also correlated with clinicopathological parameters. Results: A significant difference was observed in the expression of CD133 and Nestin in melanomas, SCC and BCC (p value=0.001). Furthermore, the level of expression was significantly higher in the melanomas compared to the SCC and BCC tumors. Expression of CD133 in the melanoma was significantly associated with increased tumor invasiveness (p value=0.05), a higher rate of metastasis (p value=0.04) and the presence of ulceration (p value=0.02). Increased expression of Nestin was observed in metastatic melanoma (p value=0.04), while no statistically significant correlation was found with other clinicopathological parameters including Breslow thickness, Clark level and ulceration. Conclusions: Elevated expression levels of CD133 and Nestin in the melanomas are associated with advanced disease, with more aggressive and metastatic skin tumors. Therefore, these markers could be potential therapeutic targets for malignant tumors of the skin.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.281.1-281.1
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• 2016

Transition metal dichalcogenides (TMDCs) are promising layered structure materials for next-generation nano electronic devices. Many investigation on the FET device using TMDCs channel material have been performed with some integrated approach. To use TMDCs for channel material of top-gate thin film transistor(TFT), the study on high-k dielectrics on TMDCs is necessary. However, uniform growth of atomic-layer-deposited high-k dielectric film on TMDCs is difficult, owing to the lack of dangling bonds and functional groups on TMDC's basal plane. We demonstrate the effect of remote oxygen plasma pretreatment of large area synthesized few-layer MoSe2 on the growth behavior of Al2O3, which were formed by atomic layer deposition (ALD) using tri-methylaluminum (TMA) metal precursors with water oxidant. We investigated uniformity of Al2O3 by Atomic force microscopy (AFM) and Scanning electron microscopy (SEM). Raman features of MoSe2 with remote plasma pretreatment time were obtained to confirm physical plasma damage. In addition, X-ray photoelectron spectroscopy (XPS) was measured to investigate the reaction between MoSe2 and oxygen atom after the remote O2 plasma pretreatment. Finally, we have uniform Al2O3 thin film on the MoSe2 by remote O2 plasma pretreatment before ALD. This study can provide interfacial engineering process to decrease the leakage current and to improve mobility of top-gate TFT much higher.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.541-551
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• 1988

The purpose of this investigation was to prepare multicomponent monolithic Li-Al-Si gels of composition(mol%) 16.67 Li2O-16.67 Al2O3-66.67 SiO2 and to convert the gels to monolithic glass-ceramic at low temperature without melting. The hydrolysis, DTA, TGA, TMA, SEM, pore distribution, density and the activation energy for crystallization of the glass-ceramic formation with rawmaterials of which tetraethl orhosilicate of networkforming cation(Si) is partially hydrolyzed, aluminum isoproxide and lithium methoxide prepared by Li-metal react with methanol were studied. The results were as follows : 1) Monolithic gels which were added with additional water, resulting in a total water content 2.5 to 3.0 times the stoichiometric amount required to fully hydrolyze the alkoxides. 2) Specimens were dried to form crylinders 60mm in length and 40mm in diameter in about 800 hrs at 5$0^{\circ}C$. 3) $\beta$-eucryptite crystals and $\beta$-spodumene crystals were detected in samples heated above 75$0^{\circ}C$. 4) Within the temperature and range of 25-50$0^{\circ}C$ and 1,00$0^{\circ}C$ the thermal expansion coefficient for crystallized samples were shown as 2.6-5.7$\times$10-7/$^{\circ}C$ and 7.4-12.5$\times$10-7/$^{\circ}C$, respectively. 5) The activation energy for the crystal growth was 11.01kcal/mol at 794$^{\circ}C$ to 85$0^{\circ}C$.

• Tuberculosis and Respiratory Diseases
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• v.68 no.1
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• pp.22-28
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• 2010

Background: Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis. VEGF production is regulated by HIF-$1{\alpha}$ and EGFR. This study examined the relationship between the clinicopathological factors and VEGF, HIF-$1{\alpha}$ and EGFR protein overexpression, and evaluated their prognostic value in patients with a surgically resected non-small cell lung cancer (NSCLC). Methods: Patients who underwent a surgical resection at Kangnam St. Mary's hospital were reviewed retrospectively. The core biopsy samples from 54 patients with NSCLC were assembled on a tissue microarray (TMA), and immunohistochemical staining for the VEGF, HIF-$1{\alpha}$ and EGFR proteins was performed. The overexpression of these proteins was evaluated in relation to age, gender, histology and staging by univariate analysis. The clinicopathological prognostic factors were analyzed. Results: Multivariate analysis performed by Cox regression (odds ratio 2.8, 95% CI 1.0~8.2, p=0.046) revealed HIF-$1{\alpha}$ overexpression to be an unfavorable factor. There was no correlation between the overexpression of these proteins and the clinicopathological factors. VEGF showed a positive relationship with EGFR, but there was no statistical significance [$p(x^2)=0.06$]. Conclusion: HIF-$1{\alpha}$ overexpression predicts shorter survival in patients with a surgically resected NSCLC. Therefore, HIF-$1{\alpha}$ may be a poor prognostic factor in NSCLC.

• Bioinformatics and Biosystems
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• v.1 no.1
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• pp.28-37
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• 2006

Recent studies in molecular biology and proteomics have identified a significant number of novel diagnostic, prognostic, and therapeutic disease markers. However, validation of these markers in clinical specimens with traditional histopathological techniques involves low throughput and is time consuming and labor intensive. Tissue microarrays (TMAs) offer a means of combining tens to hundreds of specimens of tissue onto a single slide for simultaneous analysis. This capability is particularly pertinent in the field of cancer for target verification of data obtained from cDNA micro arrays and protein expression profiling of tissues, as well as in epidemiology-based investigations using histochemical/immunohistochemical staining or in situ hybridization. In combination with automated image analysis, TMA technology can be used in the global cellular network analysis of tissues. In particular, this potential has generated much excitement in cardiovascular disease research. The following review discusses recent advances in the construction and application of TMAs and the opportunity for developing novel, highly sensitive diagnostic tools for the early detection of cardiovascular disease.

• Korean Journal of Materials Research
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• v.26 no.8
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• pp.430-437
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• 2016

Aluminum oxide ($Al_2O_3$) thin films were grown by atomic layer deposition (ALD) using a new Al metalorganic precursor, dimethyl aluminum sec-butoxide ($C_{12}H_{30}Al_2O_2$), and water vapor ($H_2O$) as the reactant at deposition temperatures ranging from 150 to $300^{\circ}C$. The ALD process showed typical self-limited film growth with precursor and reactant pulsing time at $250^{\circ}C$; the growth rate was 0.095 nm/cycle, with no incubation cycle. This is relatively lower and more controllable than the growth rate in the typical $ALD-Al_2O_3$ process, which uses trimethyl aluminum (TMA) and shows a growth rate of 0.11 nm/cycle. The as-deposited $ALD-Al_2O_3$ film was amorphous; X-ray diffraction and transmission electron microscopy confirmed that its amorphous state was maintained even after annealing at $1000^{\circ}C$. The refractive index of the $ALD-Al_2O_3$ films ranged from 1.45 to 1.67; these values were dependent on the deposition temperature. X-ray photoelectron spectroscopy showed that the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ were stoichiometric, with no carbon impurity. The step coverage of the $ALD-Al_2O_3$ film was perfect, at approximately 100%, at the dual trench structure, with an aspect ratio of approximately 6.3 (top opening size of 40 nm). With capacitance-voltage measurements of the $Al/ALD-Al_2O_3/p-Si$ structure, the dielectric constant of the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ was determined to be ~8.1, with a leakage current density on the order of $10^{-8}A/cm^2$ at 1 V.

• Polymer(Korea)
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• v.27 no.3
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• pp.249-254
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• 2003

The variation of chemical structure and physical properties of crosslinked polyethylene (XLPE) during thermal aging process was investigated. The formation of carbonyl functional group resulting from thermal oxidation reaction of XLPE was monitored using X-ray photoelectron spectroscopy and near infrared (NIR) spectroscopy. It was observed that the intensity of carbonyl peak observed at 1715 nm linearly increased with aging time in NIR spectroscopy. The linear relationship between NIR peak absorbance and aging time confirmed that NIR spectroscopy might be used as a proper tool for monitoring the aging process of polymeric materials. Also the formation of crosslinks during the aging process was monitored using thermal mechanical analysis, stress-strain test, and Shore hardness test. The change in the physical properties, such as the increase in the glass transition temperature from 110 to 132$^{\circ}C$, the decrease in the strain from 265 to 110%, as well as the increase in the shore D hardness from 32 to 50, was observed during the aging process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.174-174
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• 2009

현재 전자부품용으로 사용되는 유리프리트의 경우 PbO계를 주로 사용하고 있다. 최근 환경규제에 따른 PbO 사용이 제한됨에 따라 이를 대체할 Pb-free 유리 조성에 대한 연구가 활발히 진행 중이다. Pb-free계로서는 $Bi_2O_3$계, $B_2O_3$계가 주로 연구되고 있으나 소성 온도가 $500^{\circ}C$이상으로 높고 또한 $Bi_2O_3$ 계는 중금속이기 때문에 문제가 있다. 본 연구에서는 $400^{\circ}C$ 미만 소성이 가능한 SnO-$P_2O_5$계를 기본 조성계로 선택하고 열적, 전기적, 화학적 특성을 개선하기 위해 $R_2O_3$(R=Al, B), RO(R=Mg, Zn, Ca, Ba) 를 첨가하였다. 개선된 조성으로 샘플을 만들고 이를 대상으로 실제 전자부품 생산 공정에 적용 실험을 진행 하였다. 실험에 사용된 전자 부품은 소형 칩 베리스터로 생산 공정에서 코팅용 유리프리트와 파우더를 절연체로서 전면에 코팅하게 된다. 유리프리트를 코팅함으로서 누설 전류를 차단하고 생산 공정시 베리스터 내부를 보호하게 된다. 실험에 사용된 샘플의 열적 특성은 TMA로, 전기적 절연 특성은 고 절연저항 측정기로 측정하였고 내 산성과 내 알칼리성도 측정하였다. 샘플을 이용하여 완성된 칩 베리스터의 성능은 고온, 내습 신뢰성 TEST(고온:$150^{\circ}C$ 12HR, 내습:$85^{\circ}C$-85%12HR)로 실험하여 합부판정 (Leakage current <10uA)을 내려 완성품과 불량품을 가려내었다.