• Korean Journal of Chemical Engineering
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• 제36권2호
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• pp.191-196
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• 2019

The phase of Cu,Zn,Al precursors strongly affects the activity of their final catalysts. Herein, the Cu,Zn,Al precursor was prepared by precipitation of $Al^{3+}$ onto primitive, amorphous Cu,Zn precipitate. This precursor turned out to be a phase mixture of zincian malachite and hydrotalcite in which the latter phase was less abundant compared to the co-precipitated precursor. The final catalyst derived from this precursor exhibited a little higher copper surface area and methanol synthesis activity than the co-precipitated counterpart. Therefore, the two precursor phases need to be mixed in an adequate proportion for the preparation of active $Cu/ZnO/Al_2O_3$ catalyst.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.114-118
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• 2009

A new Zn/O single source precursor, TMEDA-Zn$(eacac)_2$, has been synthesized by using N, N, N’, N’-tetramethylethylendiamine (TMEDA), sodium ethyl-acetoacetate, and $ZnCl_2$. From this organometallic precursor, ZnO thin films have been successfully grown on Si (100) substrates through the metal organic chemical vapor deposition (MOCVD) method at relatively mild conditions in the temperature range of 390~430 ${^{\circ}C}$. The synthesized ZnO films have been found to possess average grain sizes of about 70 nm with an orientation along the c-axis. The precursor and ZnO films are characterized through infrared spectroscopy, nuclear magnetic resonance spectroscopy, EI-FAB-spectroscopy, elemental analyses, thermal analysis, X-ray diffraction, and field emission scanning electron microscopic analyses.

• 한국세라믹학회지
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• 제35권5호
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• pp.458-464
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• 1998

Variations of reaction sequence of $Pb(Zn_{0.6}Mg_{0.4})_{1/3}Nb_{2/3}O_3$[PZMN] with precusor mixing methods were ex-amined using X-ray diffraction and dielectric characteristics. In the present study three different types of precursor mixing methods (oxide mixing PbO+$ZnNb_2O_6+MgNb_2O_6$[Zn+MN] and PbO+(Zn,Mg)$Nb_2O_6$[ZMN] precursor mixing) were adopted. When the oxide mixing method was used for the PZMN synthesis a Zn-rich perovskite phase and pyrochlore phase were formed. Compared with PbO+ZN+MN precursor mixing method the PbO-ZMN precursor led to a lowering of the formation temperature for perovskite sin-gle phase. These variation of composition and formation temperature of the perovskite phase were dis-cussed in terms of the difference in the solid-reaction requence between these three different types of pre-cursor mixing.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.129-133
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• 1994

$ZnO_{x}$ films were deposited by conventional thermal evaporation method. Zinc acetate was used as precursor. XRD and SEM results shows films as mixed stats of ZnO and zinc acetate. And EDX measurements reseal composition of films as $ZnO_{x}$.

• 한국진공학회지
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• 제19권6호
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• pp.483-488
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• 2010

스핀코팅 방법을 이용하여 다양한 농도의 전구체로 ZnO 나노 섬유질 박막(ZnO nano-fibrous thin films)을 성장하였고, 그에 따른 표면 및 광학적 특성 변화를 scanning electron microscopy (SEM)와 photoluminescence (PL)을 이용하여 측정하였다. 전구체 농도가 0.4 mol (M) 이하 일 때는 성장률이 낮아 ZnO 핵생성만이 되었고, 0.6 M 이상일 때 ZnO 박막은 나노섬유질 구조가 되었다. 전구체 농도가 더욱 증가함에 따라 ZnO 나노 섬유질의 굵기가 굵어졌고 ZnO 박막의 두께도 단계적으로 두꺼워졌다. 전구체 농도가 증가함에 따라 ZnO 나노 섬유질 박막의 photoluminescence (PL)의 근밴드가장자리 광방출(near-band-edge emission) 피크 세기와 full-width at half-maximu (FWHM)이 증가하였고, 깊은 준위 광방출(deep-level mission) 피크는 적색편이(red-shift)하였다.

• 한국전기전자재료학회논문지
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• 제23권3호
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• pp.222-227
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• 2010

ZnO nanorods array have been grown on the seed crystal coated Si(100) substrate by hydrothermal method. The growth, structural and optical properties of ZnO nanorods array were investigated with a variation of precursor concentration from 0.01 M to 0.04 M. The array density of grown ZnO nanorods per same area was increased with increasing the concentration of precursor solution. Vertically aligned ZnO nanorods with hexagonal wurtzite structure have highly preferred c-axis orientation along (002) lattice plane. Especially, ZnO nanorods array developed from 0.04 M precursor solution showed a diameter of about 85 nm and length of 1.2 {\mu}m$ without any crystallographic defects. The photoluminescence spectra of ZnO nanorods from heavier precursor concentration exhibited stronger UV emission around 380 nm corresponding with near-band-edge emission.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1457-1462
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• 2007

A simple and facile sonochemical route was described for the fabrication of diameter-controlled ZnO nanorod arrays on Si wafers. The diameter of ZnO nanorods was controlled by the concentration of zinc cations and hydroxyl anions in aqueous precursor solution. At high concentration of the precursor solution, thick ZnO nanorod arrays were formed. On the contrary, thin ZnO nanorod arrays were formed at low concentration of the precursor solution. The average diameter of ZnO nanorods varies from 40 to 200 nm. ZnO nanorod arrays with sharp tip were also fabricated by the step-by-step decrease in precursor solution concentration. The crystal structure and optical characteristics of ZnO nanorods were investigated by transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy. Growth mechanism of ZnO nanorod arrays was also proposed.

• 한국결정성장학회지
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• 제26권5호
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• pp.175-180
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• 2016

본 연구에서는 수용액 상에서 침전법과 수열합성법을 이용하여 나노크기의 ZnO 분말을 합성하였다. 두 합성방법 모두 출발원료로는 Zn-nitrate hexahydrate($Zn(NO_3)_2{\cdot}6H_2O$)와 NaOH 수용액을 사용하였고, 이들의 혼합용액에 합성조건 즉 반응 pH, 온도 및 Zn precursor의 몰 농도를 달리하여 ZnO 분말을 얻을 수 있었다. 두 합성법 모두에서 단일 상 ZnO는 낮은 Zn 농도 높은 pH 및 높은 온도 조건에서 합성되기 쉬웠다. 합성된 분말의 형상은 flake(plate), multipod 및 rod 형태로 합성 조건에 따라 그 형태의 조절이 가능하였다. 침전법에 비해 수열합성법은 $100^{\circ}C$ 이하인 비교적 낮은 합성온도에서도, 본 연구의 Zn 농도 전 구간(0.1~1 M)과 넓은 pH 범위에서 결정성이 우수한 ZnO 단일 상을 합성할 수 있는 장점을 보여주었다.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.214-218
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• 2020

In this study, Mg_xZn_1-xO thin films, which can be applied not only to active layers of light-emitting devices (LEDs), such as UV-LEDs, but also to solar cells, high mobility field-effect transistors, and power semiconductor devices, are fabricated using the sol-gel method. ZnO and Mg_0.3Zn_0.7O solution synthesized by the sol-gel method and the thin film were grown by spin coating on a Si (100) substrate and sapphire substrate. The solutions are synthesized by dissolving precursor materials in 2-methoxyethanol (2-ME) solvent, and then monoethanolamine (MEA) was added to the mixed solution as a sol stabilizer. Zinc acetate dihydrate is used as a ZnO precursor, while Mg nitrate hexahydrate and Mg acetate tetrahydrate are used as an MgO precursor. Then, the optical and structural characteristics of the fabricated thin films are compared. The molar concentration of the Zn precursor in the solvent is fixed at 0.3 M, and the amount of the Mg precursor is 30% of Mg²⁺/Zn²⁺. The optical characteristics are measured using an UV-vis spectrophotometer, and the transmittance of each wavelength is measured. Structural characteristics are measured using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition analyses are performed using energy dispersive X-ray spectroscopy (EDS). The Mg_0.3Zn_0.7O thin film was well formed at the ratio of the Mg precursor added regardless of the type of Mg precursor, and the c-axis of the thin film was decreased, while the band gap was increased to 3.56 eV.

• 한국재료학회지
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• 제22권4호
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• pp.180-184
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• 2012

Nanostructures of ZnO, such as nanowires, nanorods, nanorings, and nanobelts have been actively studied and applied in electronic or optical devices owing to the increased surface to volume ratio and quantum confinement that they provide. ZnO seed layer (about 40 nm thick) was deposited on Si(100) substrate by RF magnetron sputtering with power of 60 W for 5 min. ZnO nanorods were grown on ZnO seed layer/Si(100) substrate at $95^{\circ}C$ for 5 hr by hydrothermal method with concentrations of $Zn(NO_3)_2{\cdot}6H_2O$ [ZNH] and $(CH_2)_6N_4$ [HMT] precursors ranging from 0.02M to 0.1M. We observed the microstructure, crystal structure, and photoluminescence of the nanorods. The ZnO nanorods grew with hexahedron shape to the c-axis at (002), and increased their diameter and length with the increase of precursor concentration. In 0.06 M and 0.08 M precursors, the mean aspect ratio values of ZnO nanorods were 6.8 and 6.5; also, ZnO nanorods had good crystal quality. Near band edge emission (NBE) and a deep level emission (DLE) were observed in all ZnO nanorod samples. The highest peak of NBE and the lower DLE appeared in 0.06 M precursor; however, the highest peak of DLE and the lower peak of NBE appeared in the 0.02 M precursor. It is possible to explain these phenomena as results of the better crystal quality and homogeneous shape of the nanorods in the precursor solution of 0.06 M, and as resulting from the bed crystal quality and the formation of Zn vacancies in the nanorods due to the lack of $Zn^{++}$ in the 0.02 M precursor.