• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.1014-1020
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• 2000

RF 마크네트론 스퍼터법으로 Ce의 일부를 희토류 원소로 치환한 Ce$_{1-x}$RE$_{x}$O$_{2-y}$(0.1$\leq$x$\leq$0.4, RE=Y, Nd) 박막을 Si(111), $Al_2$O$_3$(1012) 기판 위에 1450~1$600^{\circ}C$로 소결한 target을 이용하여 성장시켰다. Ce$_{1-x}$RE$_{x}$O$_{2-y}$ 박막의 성장시 기판온도 및 증착시간 등을 변화시켜 성장시켰으며, 성장된 박막의 특성분석은 XRD, SEM, TEM으로 행하였다. 증착된 박막의 방향성 및 결정성장 거동은 증착온도 및 시간에 따라 차이를 보였다. Si(111) 기판 위에 증착된 Ce$_{1-x}$Y$_{x}$O$_{2-y}$(x=0.3) 박막의 경우, 80$0^{\circ}C$에 비해 7$50^{\circ}C$에서 증착 시간에 따른 (111) 우선배향성의 정도가 나은 결과를 보였으며, $Al_2$O$_3$(1012) 기판 위에 증착한 Ce$_{1-x}$Nd$_{x}$O$_{2-y}$(x=0.3) 박막 또는 (111) 우선배향성을 나타내었다.을 나타내었다.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.217-219
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• 2006

본 논문은 초고압용 XLPE 케이블의 절연/단도전의 계면특성 향상을 위해 계면활성제 부가를 통한 절연파괴전압 향상에 관한 것으로, 계면구조의 변화와 이에 따른 절연파괴전압의 상관성을 밝히고자 하였다. 이를 위해, 계면확성제의 함량에 따른 절연/반도전 계면에서의 결정 미세구조(라멜라 밀도와 분자배향)를 스침각 X-ray와 TEM분석을 통해 밝히고, 이를 절연파괴 특성과의 상관성을 밝혔다. 연구결과, 사용되는 기저고분자와 첨가제 간의 정합성과 최적의 첨가제 함량이 절연재료의 파괴강도에 큰 영향이 있음을 알 수 있었다. 즉, 과도한 첨가제의 부가로 인하여 계면으로 이동한 계면활성제 간에 인력으로 뭉치게 되고(aggregation), 결국 국부적인 도메인을 형성하여 절연파괴 개시부로 작용할 수 있게 된다. 이를 스침각 X-ray (Gl-SAXS)를 통하여 라멜라 밀도 및 배향을 정량화 할 수 있으며, 이는 XLPE 전력케이블의 반도전 재료의 처방 및 계면특성 정량화 기법으로 유효하게 사용될 수 있을 것이다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.431-438
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• 1996

Transmission electron microscopy has been used to investigate the microstructure of hot-pressed $TiB_{2}$. Thin foil specimens, prepared by conventional ion beam thinning, revealed many features which originated from the crystallographic anisotropy of hexagonal $TiB_{2}$. It was observed that in these specimens Fe-impurities are precipitated to form secondary Fe-rich phases at grain triple edges, in grain boundaries and sometimes in-grain. These Fe-rich precipitates were characterised by their coherence or semi-coherence to a favourably oriented grain at a grain triple edge or grain boundaries or to the matrix $TiB_{2}$ phase.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.241-248
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• 1997

RuO2 thin films were deposited on SiO2(1000$\AA$)/Si and MgO(100) single crystal substrates at low tem-peratures by hot-wall metalorganic chemical vapor deposition(MOCVD), and effects of deposition paramet-ers on the properties of the thin films were investigated. RuO2 single phase was obtained at lower de-position temperature of 25$0^{\circ}C$. RuO2 thin films deposited onto SiO2(1000$\AA$)/Si substrates showed a random orientation, and RuO2 films onto MgO(100) single crystals showed the (hk0) orientation. The crystallinity and resistivity of RuO2 thin films increased and decreased with increasing deposition temperature, respec-tively. The resistivity of RuO2 thin films decreased with decreasing the flow rate. The resistivity of the 2600$\AA$-thick RuO2 thin films deposited with O2 flow rate of 50 sccm at 35$0^{\circ}C$ was 52.7$\mu$$\Omega$-cm, and they could be applicable to bottom electrodes of high dielectric materals.

• Polymer(Korea)
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• v.30 no.2
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• pp.175-181
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• 2006

Hybrid process of thermally-induced phase separation and stretching was developed for the preparation of microporous polypropylene hollow fiber membranes. Precursor for stretching was prepared by using soybean oil as a diluent and benzoic acid as a nucleating agent far the sphenlite control and it was stretched far the micrporous hollow fiber membrane. The effects of stretching ratio and deformation rate for stretching process were investigated. Increase of stretching ratio resulted in the greater pore size with nonuniform size distribution. Higher deformation rate also increaser the pore size with uniform size distribution. Stretching ratio was closely related with the orientation of polymer chain and increased the mechanical strength of the fiber. Increase of deformation rate had little effects on the orientation of crystalline phase, and decreased the orientation of amorphous phase which caused the decrease of tensile strength of the fiber and broke the micro-fibrils connecting spherulites to form a circular pore shape.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.403-409
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• 1999

The dielectric and pyroelectric properties of $Ba_{0.66}$$Sr_{0.38}$$TiO_{3}$(BST) thin films growtn on Pt/Ti/NON/Si us-ing RF magnetron sputtering have been investigated. With increasing the substrate temperature during de-position of the BST film in the range of 300-$600^{\circ}C$ the dielectric and pyroelectric constants of the film were increased due to improved crystallinity of the film. In addition the dependence of the microstructural and electrical properties of BST films onthe deposition temperature of the bottom Pt electrode was studied. The preferred orientation of the BST films as well as the microstructure of the Pt film was greatly in-fluenced by the deposition temperature of the bottom Pt electrode was studied. The preferred orientation of the BSt films as well as the microstructure of the Pt film was greatly in-fluenced by the deposition temperature of the bottom Pt electrodes. and thus so were the pyrolelectric pro-perties of the BST film. The highest value of pyroelectric coefficient at room temperature obtained in this work was $nCcm^{-2}K^{-1}$ which is much higher than those previously reported on other perovskite fer-roelectric thin films.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.22-26
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• 2001

Microstructures of AlN thin films on Si substrates grown by plasma assisted molecular beam epitaxy were analyzed with various growth temperatures and substrate orientations. Reflection high energy electron diffraction (RHEED) patterns were checked for the in-situ monitoring of the growth condition. X-ray diffraction(XRD), double crystal X-ray diffraction (DCXD), and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films after growth. On Si(100) sub-strates, AlN thin films were grown mostly along the hexagonal c-axis orientation at temperature higher than $850^{\circ}C$. On the other hand the AlN films on Si(111) were epitaxially grown with directional coherencies in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112). The microstructure of AlN thin films on Si(111) substrates, with a full width at half maximum of almost 3000 arcsec at 2$\theta$=$36.2^{\circ}$, showed that the single crystal films were grown, even if they includ a lot of crystal defects such as dislocations and stacking faults.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.774-779
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• 2013

We synthesized the solution processible monodispersed $TiO_2$ crystalline nano-sol with ~ 5 nm in size by sol-gel method. Through the spin-coating of crystalline $TiO_2$ nano-sol at low processing temperature, we could make even blocking interlayer on the rough FTO transparent electrode substrate. The rough FTO surface could be gradually smoothed by the spin-coating of nano-crystalline $TiO_2$ sol based blocking interlayer. The 1, 2.5, 5, and 10 wt% of nanocrystalline $TiO_2$ sol formed 29, 38, 62, and 226 nm-thick of blocking interlayer in present experimental condition, respectively. The 5 and 10 wt% of $TiO_2$ nano-sol could effectively fill up the valley part of bare FTO with 48.7 nm of rms (root mean square) roughness and consequently enabled the ZnO to be grown to vertically aligned one dimensional nanorods on the flattened blocking interlayer/FTO substrate.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.358-364
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• 2009

We investigated the growth of ZnO thin films with prominent emission characteristics through minimizing the formation of defects by using pulsed laser deposition (PLD). To do so, the ZnO films were deposited on sapphire(0001) substrates at the substrate temperature of $400-850^{\circ}C$ and then the variation of their structural and optical properties were analyzed by x-ray diffraction, atomic force microscope and photoluminescence. As a result, all ZnO films were grown with c-axis preferential orientation irrespective of the substrate temperature. However, the crystallinity and stress state were dependent on the substrate temperature and the ZnO film deposited at $600^{\circ}C$ showed the best surface morphology and crystallinity with nearly no strain. And also this film exhibited outstanding emission characteristics from the viewpoint of full width half maximum of UV emission peak as well as visible emission due to defects. These results indicate that the emission characteristics of the ZnO films are strongly related to their structural characteristics influenced by substrate temperature. Consequently, ZnO films with strong UV emission and nearly no visible emission, which are applicable to UV emission devices, could be grown at the substrate temperature of $600^{\circ}C$ by PLD.

• Journal of the Korean Chemical Society
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• v.23 no.5
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• pp.286-295
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• 1979

In order to predict the effect of Lewis acid catalysis on the regioselectivity of the Diels-Alder reactions between unsymmetrically substituted dienes and dienophiles, the frontier orbital theory applied to the theoretical model of the Lewis acid complexed dienophile was studied by means of CNDO/2 MO. In the majority of reactions, CNDO/2 calculations gave good results in accordance with experimental orientation. Also, it was shown that the secondary orbital interaction played an important role in the regioselectivity of the Diels-Alder reaction between unsymmetrically substituted dienes and dienophiles. Although ANH's treatment is mathematically simpler than other methods, ANH's method which laid emphasis on dissymmetrical transition state gave good results on decision of regioselectivity.