• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.116-120
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• 2011

In this paper, we studied the optimization of the screen pringting method for crystalline silicon solar cell fabrication. The 156 * 156 mm2 p-type silicon wafers with $200{\mu}m$ thickness and $0.5-3{\Omega}cm$ resistivity were used after texturing, doping, and passivation. Screen printing method is a common way to make the c-Si solar cell with low-cost and high-efficiency. We studied the optimized condition for screen printing with crystalline silicon solar cell as changing the printing direction (finger line or bus bar), finger width, and mesh angle. As a result, the screen printing with finger line direction showed higher finger height and better conversion efficiency, compared with one with bus bar direction. The experiments with various finger widths and mesh angles were also carried out. The characteristics of solar cells was obtained by measuring light current-voltage, optical microscope and electroluminescence.

• 대한치과보철학회지
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• 제34권1호
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• pp.169-186
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• 1996

The purpose of this study was to investigate the mechanical properities and biocompatibility with crystallization temperature and time of a bioactive glass-ceramic system $41.4wt%SiO_{2}-35.0wt%CaO-3.0wt%MgO-12.0wt%P_{2}O_{5}-8.6wt%Al_{2}O_{3}$ with same molar percent of $Al_{2}O_{3}\;and\;P_{2}O_{5}$. The crystallization behaviors were investigated with DTA, XRD and SEM. Fracture toughness with the change of crystallization temperature and time was measured by indentation fracture method. Also, biocompatibility was evaluated by culture of mouse fibroblast cell line L929. The results obtained were as follows ; 1. The major crystalline phases were apatite and anorthite, and relative intensity of anorthite phase was increased at $1004^{\circ}C$. 2. The hardness and fracture toughness were gradually increased with the increase in ceraming temperature to $1004^{\circ}C$. 3. When the glass ceramic was heat-treated for 4 hours at ceraming temperature of $1004^{\circ}C$, hardness and fracture toughness showed the maximum values $578.84k/mm^2\;and\;2.07MPa\;m^{1/2}$, respectively. 4. The growth rate and cytotoxic of L929 fibroblast cells for bioactive glass ceramic were better than those of stainless steel and titanium.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.641-647
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• 1999

The paper provides the results of microstructure analysis and dielectricproperties of porcelain suspension insulators. The evaluation of characteristics was also made as a function of the manufacturers and fabricated years for the experimental specimens which had been used in real distribution lines. Even though the series A contained higher alumina contents than the series B, the densification of series A was lower than that of series B, resulting from much porosity. The microstructure investigation confirmed that series A had much porosity than series B. The series A contained quartz $(SiO_2),\; mullite\; (Al_6Si_2O_{13}),\; corundum(Al_2O_3),\; and cristobalite\; (SiO_2)$ phases. However, the series B had no cristobalite phase which had very high thermal expansion coefficient. Also, the tan$\delta$of series A was more abruptly increased than that of series B as increasing temperature. The elevated temperature may make much expansion of cristobalite crystal than other crystals, resulting in crack and puncture inside cap during the summer days.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.593-596
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• 1999

This paper presents a process optimization of antireflectiun (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a doble-layer AR(DLAR) coating of MgF$_2$/CeO$_2$, We investigated CeO$_2$ films as an All layer because they hale a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown CeO$_2$ film showed strong dependence on a deposition temperature. The CeO$_2$ film deposited at 400 $^{\circ}C$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgF$_2$ film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 7m to 1.1 7m. We achieved the efficiencies of solar cells greater than 15% with 3.12 % improvement with DLAR coatings . Further details on MgF$_2$, CeO$_2$ films, and cell fabrication Parameters are presented in this paper.

• 마이크로전자및패키징학회지
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• 제7권2호
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• pp.43-46
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• 2000

Nd:YAG laser of 355 nm wavelength, which amounts to 3.5 eV, produced by a harmonic generator was used to create Ag metallic particles as seeds for nucleation in photosensitive glass containing $Ag^+$ and $Ce^{3+}$ . The pulse widths and frequency of the laser were 8ns and 10 Hz, respectively. For crystalline growth, heat-treatment following laser irradiation was carried out at $570^{\circ}C$ for 1h. Then, the $LiAlSi_3O^8$ crystal phase appeared in the laser irradiated lithium aluminum silicate glass. We present the effect of laser-induced nucleation compared with spontaneous nucleation by heat treatment fur crystallization in the glass.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.323-330
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• 1998

Mixed oxide compounds of potential usefulness for fibre coatings (hexagonal celsian, $BaAl_2Si_2O_8$ and lanthanum hexaluminate, $LaAl_{11}O_{18}$) or for matrix materials (yttrium aluminium garnet, $Y_3Al_5O_{12}$) were prepared by hybrid sol-gel synthesis and their thermal crystallisation was monitored by thermal analysis, X-ray diffraction and multinuclear solid state MAS NMR. All the gels convert to the crystalline phase below about $12200^{\circ}C$, via amorphous intermediates in which the Al shows and NMR resonance at 36-38 ppm sometimes ascribed to Al in 5-fold coordination. Additional information about the structural changes during thermal treatment was provided by $^{29}Si$, $^{137}Ba$ and $^{89}Y$ MAS NMR spectroscopy, showing that the feldspar framework of celsian begins to be established by about $500^{\circ}C$ but the Ba is still moving into its polyhedral lattice sites about $400^{\circ}C$ after the sluggish onset of crystallization. Lanthanum hexaluminate and YAG crystallise sharply at 1230 and $930^{\circ}C$ respectively, the former via $\gamma-Al_2O_3$, the latter via $YAlO_3$. Yttrium moves into the garnet lattice sites less than $100^{\circ}C$ after crystallisation.

• 한국결정성장학회지
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• 제5권2호
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• pp.175-180
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• 1995

석탄회의 성상 해명의 일환으로서, 석회석의 열처리 조건과 광물조성의 관계를 검토했다. 석탄회의 주 광물조성은 mullite, quartz 및 유리상(약 20 ~ 25wt%)이었으며, $1000^{\circ}C $ 까지는 거의 변화가 없었다. 안산의 석탄회 중에는 calcite가 함유되었으며, $1200^{\circ}C $ 에서 calcite 분해로부터 온 CaO, quartz 및 유리상 중의$Al_2O_3$가 반응하여 anorthite($CaO{\cdot}Al_2O_3{\cdot}2SiO_2$)로 바뀌는 것을 알 수 있었다.

• 센서학회지
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• 제9권3호
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• pp.242-247
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• 2000

10 mole%의 과잉 PbO가 첨가된 타겟을 이용하여 $(La_{0.5}Sr_{0.5})CoO_3(LSCO)/Pt/Ti/SiO_2/Si$ 위에 RF 마그네트론 스퍼터링 방법을 이용하여 $Pb_{0.99}[(Zr_{0.6}Sn_{0.4})_{0.9}Ti_{0.1}]_{0.98}Nb_{0.02}O_3(PNZST)$ 박막을 증착시켰다. $500^{\circ}C$의 기판온도, 80W의 RF power에서 증착된 박막은 급속열처리(RTA)후에 페로브스카이트 상으로 결정화되었다. $650^{\circ}C$, 공기중에서 10초 동안 열처리된 박막이 가장 우수한 결정성과 전기적 특성을 나타내었다. 이러한 박막으로 제작된 PNZST 커패시터는 약 $20\;{\mu}C/cm^2$ 정도의 잔류분극과 약 50 kV/cm 정도의 항전계를 나타내었다. 또한, $2.2{\times}10^9$의 스위칭 후에도 잔류분극의 감소는 10% 미만이었다.

• 한국재료학회지
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• 제17권1호
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• pp.1-5
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• 2007

GaN thin fan were grown by spin coated colloidal GaOOH precursor. Polycrystalline GaNs with crystalline size of $10{\sim}100nm$ were grown on $SiO_2$ substrate. The shape of crystallite above $900^{\circ}C$ had the hexagonal plate and column type. X-ray diffraction patterns for them correspond to those of the hexagonal wurtzite GaN. With increasing droplets. i.e, thickness of deposited layers, XRD intensity increased. PL (photoluminescence) spectrum consisted with an weak near band-edge emission at 3.45 eV and a broad donor-acceptor emission band at 3.32 eV. From the low temperature PL measurement on GaN grown at $800^{\circ}C$ that the shallow donor-acceptor recombination induced emission was more intense than the near band-edge excitonic emission.

• 한국재료학회지
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• 제13권5호
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• pp.303-308
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• 2003

Amorphous carbon nitride films deposited on Si(001) substrates by a plasma enhanced chemical vapor deposition (PECVD) technique using CH$_4$and $N_2$as reaction gases were thermally annealed at various temperatures under$ N_2$atmosphere, then their physical properties were investigated particularly as a function of annealing temperature. Above $600^{\circ}C$ a small amount of crystalline $\beta$-$C_3$$N_4$ phase evolves, while the film surface becomes very rough due to agglomeration of fine grains on the surface. As the annealing temperature increases, both the hardness and the $sp^3$ bonding nature are enhanced. In contrast to our expectation, higher annealing temperature results in a relatively higher friction mainly due to big increase in roughness at that temperature.