• 한국세라믹학회지
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• 제53권4호
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• pp.463-467
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• 2016

$Si^{4+}-N^{3-}$ was incorporated into $Ce^{3+}-doped$ lutetium aluminum garnet ($Lu_{2.965}Ce_{0.035}Al_5O_{12}$, $LuAG:Ce^{3+}$) lattices, resulting in the formation of $Lu_{2.965}Ce_{0.035}Al_{5-x}Si_xO_{12-x}N_x$ [(Lu,Ce)AG:xSN]. For x = 0-0.25, the synthesized powders consisted of the LuAG single phase, and the lattice constant decreased owing to the smaller $Si^{4+}$ ions. However, for x > 0.25, a small amount of unknown impurity phases was observed, and the lattice constant increased. Under 450 nm excitation, the PL spectrum of $LuAG:Ce^{3+}$ exhibited the green band, peaking at 505 nm. The incorporation of $Si^{4+}-N^{3-}$ into the $Al^{3+}-O^{2-}$ sites of $LuAG:Ce^{3+}$ led to a red-shift of the emission peak wavelength from 505 to 570 nm with increasing x. Corresponding CIE chromaticity coordinates varied from the green to yellow regions. These behaviors were discussed based on the modification of the $5d^1$ split levels and crystal field surroundings of $Ce^{3+}$, which arose from the Ce-(O,N)8 bonds.

• 한국세라믹학회지
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• 제20권2호
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• pp.129-134
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• 1983

MgO.$Al_2O_3$ polycrstalline spinel powder was subjected to vaporization over the temperature range of 1150-130$0^{\circ}C$ under H2 atmosphere. Diffusion coefficient of oxygen ion through the spinel were calculated using the measure vaporization rates as follows : D=28.4 exp(-901500/RT) Reference data of the vaporization rates of MgO.$8Al_2O_3$ single crystal spinel were applied to the vaporiza-tion model proposed in this study and were calculated to give the oxygen ion diffusion coefficients over the tempera-ture 1700-195$0^{\circ}C$. The obtained diffusion coefficients are as follows: $D=3.20{\times}106$ exp(-155600/RT)

• 한국세라믹학회지
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• 제23권5호
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• pp.25-34
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• 1986

This study was to refined the crystal structure of solid solution to determine the position and amount of Al in diopside and to relate crystal structure changes and properties of solid solution. Single crystals of the solid solution in the system CaO.MgO.$2 SiO_2-Al_2O_3$ were made from the melt with slow cooling and used to refine the structure. The following were obtained. 1. Tetrahedra rotated around axis parallel to the direction which the angle 03-03-03 became small. 2. Tetrahedron became large and regular. Average T-O bond distance increased 0.53 percent. 3. M1 octahedron became small and average M1-O bond distance decreased 1.1 percent. 4, M2 polyhedron became small and average M2-O bond distance decreased 0.37 percent Polythedron was affected not so much compared with any cation site. 5. Distance between metal ions distances between T and oxygens which were coordinated with M2 and meighboring tetrahedron distances between M2 and oxygens which coordinated with M1 and M2 were not changed almost. 6. $Al^{3+}$ substituted 4Mg^{2+}$ and $Si^{4+}$

• 한국결정성장학회지
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• 제19권2호
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• pp.84-89
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• 2009

The turbid/translucent, near colorless(milky) metamorphic sapphire samples from Sri Lanka have been characterized after the heat treatment in $N_2$ at $1650^{\circ}C$. As-received sapphire specimens became bluish-colored and exhibited more clarity after the heat treatment. It was found that the color change at inclusions zoning region is attributed by the dissolution. As received samples contain the micro/nano inclusions such as rutile($TiO_2$), ilmenite($FeTiO_3$), spinel($MgAl_{2}O_{4}$)/ulvospinel($Fe_{2}TiO_{4}$) and apatite($Ca_5(PO_4)_3$), which were dissolved by the heat treatment and form the blue color through $Fe^{2+}/Ti^{4+}$ charge transferring. The microstructures become different because as the dissolution of apatite($Ca_5(PO_4)_3(OH,F,Cl)$) in alumino silicates($Al_{2}SiO_{5}$) occurred, resulting in morphological change with the appearance of(Ca, Mg, Al) silicate on the surface. Both as-received and heat treated samples showed the rhombohedral crystal structure of $Al_{2}O_{3}$.

• 한국결정성장학회지
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• 제27권2호
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• pp.99-104
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• 2017

저급탄을 가스화하는 반응기에 사용되는 내화물은 고온에서 부식성이 강한 $H_2S$ 가스에 노출되며, 경도나 내마모성과 같은 기계적 특성이 가스에 노출되는 시간이 길어짐에 따라서 떨어진다. 그러나 $H_2S$ 가스에 의한 내화물의 기계적 특성 약화 원인이 아직 잘 알려져 있지 않다. 본 실험에서는 내화도가 다른 두 종류의 케스터블 내화물을 $H_2S$ 농도가 높은 $H_2O/N_2/H_2S$ 혼합가스에 100시간 동안 $900^{\circ}C$에서 노출시키고, 미세구조, 결정상과 내마모 특성 변화를 비교하였다. 혼합가스에 노출되면서 내화물 시편의 무게는 감소하였다. 노출 후 기공률은 감소하고, 내마모 특성은 현저하게 떨어졌다. 부식에 의해서 내화물을 구성하는 상에 변화가 일어났는데, $CaAl_2O_4$와 일부의 $SiO_2$는 사라지고 $CaSO_4{\cdot}2H_2OS$와 $Al_2Si_2O_5(OH)_4$ 상이 나타났다. 내화물의 내마모 특성이 $H_2S$ 가스에 노출된 후에 감소하는 주 원인은 캐스터블 내화물에서 결합제 역할을 하는 $CaAl_2O_4$가 사라지고 기계적 특성이 나쁜 $CaSO_4{\cdot}2H_2OS$가 생성되기 때문인 것으로 생각되었다.

• 한국결정성장학회지
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• 제27권6호
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• pp.282-288
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• 2017

본 논문에서는 광전 음극 이미지 센서로 사용될 수 있는 광소자용 재료로 III-V 족 화합물 반도체인 GaAs/AlGaAs 다층 구조를 LPE(Liquid Phase Epitaxy) 방법에 의해 성장하였다. n형 GaAs 기판 위에 수십 nm의 GaAs 완충층을 형성 한 후 Zn가 도핑된 p-AlGaAs 에칭 정지 층(etching stop layer)과 Zn가 도핑된 p-GaAs 층 그리고 Zn가 도핑된 p-AlGaAs 층을 성장하였다. 성장된 시료의 특성을 조사하기 위하여 주사전자현미경(SEM)과 이차이온질량분석기(SIMS) 그리고 홀(Hall) 측정 장치 등을 이용하여 GaAs/AlGaAs 다층 구조를 분석하였다. 그 결과 $1.25mm{\times}25mm$의 성장 기판에서 거울면(mirror surface)을 가지는 p-AlGaAs/p-GaAs/p-AlGaAs 다층 구조를 확인할 수 있었으며, Al 조성은 80 %로 측정 되었다. 또한 p-GaAs층의 캐리어 농도는 $8{\times}10^{18}/cm^2$ 범위까지 조절할 수 있음을 확인하였다. 이 결과로부터 LPE 방법에 의해 성장된 p-AlGaAs/p-GaAs/AlGaAs 다층 구조는 광전 음극 이미지 센서의 소자로서 이용될 수 있을 것으로 기대한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.473-473
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• 2011

In recent years, organic thin film transistors OTFTs based on conductive-conjugated molecules have received significant attention. We report a fabrication of organic single crystal nanowires that made on Si substrates by liquid bridge-mediated nanotransfer molding (LB-nTM) with polyurethane acrylate (PUA) mold. LB-nTM is based on the direct transfer of various materials from a stamp to a substrate via a liquid bridge between them. In liquid bridge-transfer process, the liquid layer serves as an adhesion layer to provide good conformal contact and form covalent bonding between the organic single crystal nanowire and the Si substrate. Pentacene is the most promising organic semiconductors. However pentacene has insolubility in organic solvents so pentacene OTFTs can be achieved with vacuum evaporation system. However 6, 13-bis (triisopropylsilylethynyl) (TIPS) pentacene has high solubility in organic solvent that reported by Anthony et al. Furthermore, the substituted rings in TIPS-pentacene interrupt the herringbone packing, which leads to cofacial ${\pi}-{\pi}$ stacking. The patterned TIPS-Pentacene single crystal nanowires have been investigated by Atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrical properties.

• Journal of Electrochemical Science and Technology
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• 제14권4호
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• pp.377-387
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• 2023

Ni-W/Al₂O₃ nano-composites were electrodeposited on mild steel substrate for mechanical and corrosion resistance applications. This study focused on the preparation of Ni-W/Al₂O₃ nano-composite coating with various quantity of Al₂O₃ incorporations. The addition of Al₂O₃ in the electrolytes were varied from 1-10 g/L in electrolytes and the Al₂O₃ incorporation in Ni-W/Al₂O₃ nano-composite coatings were obtained from 1.82 to 13.86 wt.%. The incorporation of Al₂O₃ in Ni-W alloy matrix influenced the grain size, surface morphology and structural properties were observed. The distributions of Al₂O₃ particle in alloy matrix were confirmed using electron microscopy (FESEM and TEM) and EDAX mapping analysis. The crystal structure informations were studied using X-ray diffraction method and it confirms that the deposits having cubic crystal structure. The better corrosion rate (0.87 mpy) and microhardness (965 HV) properties were obtained for the Ni-W/Al₂O₃ nano-composite coating with 13.86 wt.% of Al₂O₃ incorporations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.185-188
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• 1996

The doped n-type $Al_{x}Ga_{1-x}Sb$ crystals were grown by the vertical Bridgman method at composition ratio x=0, x=0.1, x=02 respectively. The lattice constants of the $Al_{x}Ga_{1-x}Sb$ crystals were 6.096${\AA}$, 6.097${\AA}$, 6.106${\AA}$ at composition ratio respectively. The carrier concentration, the resistivity, and the carrier mobility measured by the Van der Pauw method at x-0 were n≡1 x $10^{17}$$cm^{-3}$, $\rho$≡0.15 ${\Omega}$-cm, ${\mu}$$_{n}$≡500 $\textrm{cm}^2$$V^{-1}$$sec^{-1}$ at 300K. The carrier concentration, the resistivity, and the carrier mobility measured by the Van der Pauw method at x=0.1 were n≡2.96 x $10^{15}$$cm^{-3}$, $\rho$≡103 $\textrm{cm}^2$$V^{-1}$$sec^{-1}$ at 300K.

• 한국결정학회지
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• 제5권1호
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• pp.24-32
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• 1994

(0001),(1012) 및 (1120)면 sapphire 기판위에 성장되는 (0001), (1120) 및 (1011)면 GaN epitaxy 박막을 Ga/HCI/NH3/He 계를 사용한 HVPE(halide vapor phase epitaxy)방법에 의하여 성장시키는 연구를 수행하였다. 박막의 표면조직과 결정구조는 XRD, RHEED와 SEM으로 분석하였으며, 성장된 막의 화학적 조성은 XPS로 관찰되었다. (1120) sapphire위에는 각각 (0001)과 (1120) GaN epitaxy 박막의 두가지 배향관계가 관찰되었다. (0001)면 GaN epitaxy 박막은 (0001)과 (1120)면 sapphire 기판위에서 1050℃ 의 고온으로 성장시킬 때 이차원적인 성장구조를 보여주였으며, (1120) sapphire 기판위에 성장된 (1011) GaN 박막이 주사전자현미경과 RHEED 분석결과 가장 좋은 표면조직과 결정구조를 보여주었다.