• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.106-106
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• 1999

반도체 소자가 소브마이크론 이하로 집적화 되어감에 따라, RC 신호 지연 및 간섭 현상, 전력 소비의 증가 문제가 심각하게 대두되고 있다. 이러한 문제를 개선하기 위해서는, 현재 층간 절연막으로 상용화되어 있는 SiO2 박막을 대체할 저유전율 박막의 개발이 필수적이며, 많은 연구자들이 여러 가지 새로운 유기물질과 무기물질은 제안하고 있다. 반도체 공정상의 적합성을 고려할 때, 이들 여러물질 중에서 알킬기를 함유한 SiO2 박막(이하 'Si-O-C-H 박막'으로 표기)에 많은 관심이 집중되고 있다. Si-O-C-H 박막은 알킬기에 의해 형성된 나노 스케일의 기공에 의해 작은 유전율을 가지게 된다. 따라서, 박막내의 알킬기의 함유량이 많을수록 보다 작은 유전율을 얻을 수 있다. 그러나 과다한 알킬기의 함유는 Si-O-C-H 박막의 열적 특성을 열화시키는 부정적인 효과도 있다. 본 연구에서는 bis-trimethylsilylmethane(BTMSM, H9C3-Si-CH2-Si-C3H9) precursor를 이용하여 Si-O-C-H 박막을 증착하였다. BTMSM precursor의 중요한 특징중 하나는, 두 실리콘 원자 사이에 Si-CH2 결합이 존재한다는 사실이다. Si-CH2 결합은 양쪽의 Si에 의해 강하게 결합되어 있어서, BTMSM precursor를 사용하여 Si-O-C-H 박막은 유전상수도 작을 뿐 아니라, 열적으로도 안정된 특성이 얻어질 것으로 기대된다. Si-O-C-H 박막의 열적 안정성을 평가하기 위하여, 고온 열처리 전후의 FT-IR 스펙트럼 분석과 C-V(capacitance-voltage) 측정에 의한 유전상수 변화를 살펴보았다. 또한 증착된 박막의 미세구조 및 step coverage 특성 관찰을 위하여 SEM(scanning electron microscopy) 및 TEM(transmission electron micfroscopy) 분석을 하였다. 변화하였으며 이는 포토루미네슨스의 변화의 원인으로 판단된다. 연구하였다. CeO2 와 Si 사이의 계면을 TEM 측정에 의해 분석하였고, Ce와 O의 화학적 조성비를 RBS에 의해 측정하였다. Si(100) 기판위에 증착된 CeO2 는 $600^{\circ}C$ 낮은 증착률에서 seed layer를 하지 않은 조건에서 CeO2 (200) 방향으로 우선 성장하였으며, Si(111) 기판 위의 CeO2 박막은 40$0^{\circ}C$ 높은 증착률에서 seed layer를 2분이상 한 조건에서 CeO2 (111) 방향으로 우선 성장하였다. TEM 분석에서 CeO2 와 Si 기판사이에서 계면에서 얇은 SiO2층이 형성되었으며, TED 분석은 Si(100) 과 Si(111) 위에 증착한 CeO2 박막이 각각 우선 방향성을 가진 다결정임을 보여주었다. C-V 곡선에서 나타난 Hysteresis는 CeO2 박막과 Si 사이의 결함때문이라고 사료된다.phology 관찰결과 Ge 함량이 높은 박막의 입계가 다결정 Si의 입계에 비해 훨씬 큰 것으로 나타났으며 근 값도 증가하는 것으로 나타났다. 포유동물 세포에 유전자 발현벡터로써 사용할 수 있음으로 post-genomics시대에 다양한 종류의 단백질 기능연구에 맡은 도움이 되리라 기대한다.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 대

• 한국초전도학회:학술대회논문집
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• 2009.07a
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• pp.97-97
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• 2009

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.1-13
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• 2016

This review deals with one of the surface modification techniques, chemical conversion coating and particularly cerium-based conversion coatings (CeCC) as a promising substitute for chromium and phosphate conversion coating on magnesium and its alloys. The CeCCs are commonly considered environmentally friendly. The effects of surface preparation, coating thickness, bath composition, and e-paint on the corrosion behavior of CeCCs have been studied on the AZ31 magnesium alloy. This review also correlates the coating microstructural, morphological, and chemical characteristics with the processing parameters and corrosion protection. Results showed that the as-deposited coating system consists of a three layer structure (1) a nanocrystalline MgO transition layer in contact with the Mg substrate, (2) a nanocrystalline CeCC layer, and (3) an outer amorphous CeCC layer. The nanocrystalline CeCC layer thickness is a function of immersion time and cerium salt used. The overall corrosion protection was crucially dependent on the presence of coating defects. The corrosion resistance of AZ31 magnesium alloy was better for thinner CeCCs, which can be explained by the presence of fewer and smaller cracks. On the other hand, maximum corrosion protection was achieved when AZ31 magnesium samples with thin CeCCs are e-painted. The e-paint layer further restricts and hinders the movement of chloride and other aggressive ions present in the environment from reaching the magnesium surface.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.201-206
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• 2000

Effects of the post-annealing temperature of CeO$_2$ buffer layers on the properties of YBCO films on CeO$_2$-buffered sapphire were investigated. 45 nm-thick CeO$_2$ buffer layer was prepared in-situ on r-cut sapphire using an on-axis rf magnetron sputtering method, which was later post-annealed at temperatures between 950$^{\circ}$C and 1100$^{\circ}$C in an oxygen-flowing environment. YBCO films were prepared on CeO$_2$-buffered sapphire (CbS), for which the surface morphology, crystal structures and electrical properties of the YBCO films were studied. YBCO films on post-annealed CbS appeared to have better properties than those on as-grown CbS with regard to the morphological, structural and electrical properties when the YBCO films were prepared on CeO$_2$ buffer layer post-annealed at temperatures of 1000 - 1050$^{\circ}$C. A TE$_{011}$ mode rutileloaded cylindrical cavity resonators was fabricated with the YBCO films placed as the endplates, for which the unloaded Q of the resonator was measured. It turned out that the resonator with the endplates prepared from the YBCO films on postannealed CbS at 1000 $^{\circ}$C showed the highest unloaded Q with the value more than 8 ${\times}$ 10$^5$ at 30 K and 8.6 CHz, revealing that the YBCO films on post-annealed CbS at 1000$^{\circ}$C the temperature could be the lowest among the YBCO films on post-annealed CbS.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.981-987
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• 1998

$La_{0.5}Sr_{0.5}MnO_{3-\delta}$ as air electrode for soild oxide fuel cell was synthesized by a citrate process and its cathodic polarization was determinated by the current interruption method on the Gd-doped ceria as electrolyte. The addition of citric acid increased the exothermic heat for the formation of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ perovskite oxide. The degree of the initial particle agglomeration was affected by the exothermic heat. Also the increase of cal-cination temperature enlarged the particle size and the higher sintering temperature accelerated the den-sification of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ layer after its being painted on $Ce_{0.8}Gd_{0.2}O_{1.9}$ electrolyte. In this study $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ synthesized by citrate process of which the molar ratio of citric acid to metal nitrate was 2 calcined at $650^{\circ}C$ for 2hr and sintered at 1100 at $1200^{\circ}C$ for 4 hrs after slurry coating on Ce0.8Gd0.2O1.9 electrlyte showed the lowest cathodic polarization.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.95-105
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• 1995

Ceria(CeO2) stabilized zirconia(CeSZ) sol was synthesized with zirconium n-butoxide Zr(OC4H9)4 and cerium nitrate hexahydrate Ce(NO3)3.6H2O as precursors and ethylacetoacetate(EAcAc) as a chelating agent under atmosphere. CeSZ films were deposited on AISI 304 stainless steel using the prepared polymeric sol by dipcoating and the coating characteristics were investigated by XRD, ellipsometry, scratch test and SEM. The CeSZ film began to crystallize from amorphous to tetragonal phase at 40$0^{\circ}C$ and it was not converted into monoclinic phase up to 100$0^{\circ}C$ by the addition of 16mol% CeO2 as a stabilizer which could suppress phase transformation of zirconia. The CeSZ films were prepared by varying the EAcAc contents and the cncentration of CeSZ sol and measured the thickness and refractive index. From these results, it was found that the EAcAc contents and concentration of CeSZ coating sol evidently affect the densification of CeSZ film. The CeSZ film coated with 0.4M CeSZ sol and heat-treated at $600^{\circ}C$ for 10min had thickness of 50nm and 17% porosity. The CeSZ film on 304 stainless steel effectively acted as a protective layer against oxidation up to 80$0^{\circ}C$ and had superior corrosion resistance in 25% H2SO4 solution for 4.5 hrs.

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.65-65
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• 2002

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.117-122
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• 2010

BCY($Ba(Ce_{0.9}Y_{0.1})O_{3-\delta}$) oxide, shows high protonic conductivity at high temperatures, and are referred to as hydrogen separation membrane. For high efficiency of hydrogen separation ($H_2$ flux and selectivity) and low fabrication cost, ultimate thin and dense BCY-Ni layer have to be coated on a porous substrate such as $ZrO_2$. Aerosol depostion (AD) process is a novel technique to grow ceramic film with high density and nano-crystal structure at room-temperature, and would be applied to the fabrication process of AD integration ceramic layer effectively. XRD and SEM measurements were conducted in order to analyze the characteristics of BCY-Ni membrane fabricated by AD process.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.69-69
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• 2004