• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.221.2-221.2
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• 2015

Graphene is very interesting 2 dimensional material providing unique properties. Especially, graphene has been investigated as a stretchable and transparent conductor due to its high mobility, high optical transmittance, and outstanding mechanical properties. On the contrary, high sheet resistance of extremely thin monolayer graphene limits its application. Artificially stacked multilayer graphene is used to decrease its sheet resistance and has shown improved results. However, stacked multilayer graphene requires repetitive and unnecessary transfer processes. Recently, growth of multilayer graphene has been investigated using a chemical vapor deposition (CVD) method but the layer controlled synthesis of multilayer graphene has shown challenges. In this paper, we demonstrate controlled growth of multilayer graphene using a two-step process with multi heating zone low pressure CVD. The produced graphene samples are characterized by optical microscope (OM) and scanning electron microscopy (SEM). Raman spectroscopy is used to distinguish a number of layers in the multilayer graphene. Its optical and electrical properties are also analyzed by UV-Vis spectrophotometer and probe station, respectively. Atomic resolution images of graphene layers are observed by high resolution transmission electron microscopy (HRTEM).

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2609-2612
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• 2012

A simple green method was developed for rapid synthesis of silver and gold nanoparticles (AgNPs and AuNPs) has been reported using Lonicera japonica flower extract as a reducing and a capping agent. AgNPs and AuNPs were carried out at $70^{\circ}C$. The successful formation of AgNPs and AuNPs have been confirmed by UV-Vis spectro photometer, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray Analysis (EDAX), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). To our knowledge, this is the first report where Lonicera japonica flower was found to be a suitable plant source for the green synthesis of AgNPs and AuNPs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.284-287
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• 2013

In this work, we have fabricated TiC films by using unbalanced magnetron sputtering method with graphite and Ti targets for contact strip application of electric railway. TiC films were deposited with various substrate temperatures. We investigated various properties of TiC films prepared with various substrate temperatures, such as the hardness, surface roughness, friction coefficient, resistivity, FESEM (Field Emission Scanning Electron Microscopy), HRTEM (High Resolution Transmission Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy). The hardness and friction coefficient properties of TiC films were improved with increasing substrate temperature. These results indicate that the improvement of hardness and resistivity is related to the increase of sp2 clusters in TiC films. And also, the resistivity value of TiC films were decreased with increasing substrate temperature.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.129-133
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• 2000

Boron nitride films were synthesized with $N_2$ion flux of low energy, up to 100 eV, at different substrate temperatures of no heating, 200, 400, 500, and $800^{\circ}C$, respectively. Boron was supplied by e-beam evaporation at the rate of $1.5\AA$/sec. For all the conditions, hexagonal BN (h-BN) phase was mainly synthesized and high resolution transmission electron microscopy (HRTEM) showed that (002) planes of h-BN phase were aligned vertical to the Si substrate. The maximum alignment occurred around $400^{\circ}C$. In addition to major h-BN phase, transmission electron diffraction (TED) rings identified the formation of cubic BN (c-BN) phase. But HRTEM showed no distinct and continuous c-BN layer. These results suggest that c-BN phase may form in a scattered form even when h-BN phase is mainly synthesized under small momentum transfer by bombarding ions, which are not reconciled with the macro compressive stress model for the c-BN formation.

• Journal of the Mineralogical Society of Korea
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• v.13 no.2
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• pp.53-64
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• 2000

Chlorite from the talc deposits in the Chungnam area, Korea, has been studied using electron microprobe analysis and high resolution transmission electron microscopy (HRTEM), Talc orea are hydrothermal alteration products of serpentinite which was originated from ultramafic rocks. Chlorite occurs in close association with talc ores of with the black alteration zone between talc ore bodies and granitic gneiss. It is the most abundant impurity mineral of talc ores. Chlorite in association with talc is characterized by very high but narrow variation in Mg/(Mg+Fe) ratios (0.784~0.951), significant octahedral substitution (-0.200~0.692), wide variation in Al contents (1.085~3.160 / 14 oxygens), and high Cr and Ni contents. It was formed under a very limited but high Mg/(Mg+Fe) condition in close connection with serpentinite. Chlorite in the black alteration zone is characterized by a high Fe content, wide variation in Mg/(Mg+Fe) ratios (0.378~0.852), narrow octahedral substitution (-0.035~0.525), high narrow Al contents (1.468~2.959), and low Cr and Ni contents. It was formed under a low Mg/(Mg+Fe) and relatively Al-rich condition in close connection with county rocks. Two different chemical modes for chlorite suggest two different origins for two different chlorites. Although most of chlorites show typical 14-$\AA$ lattice fringe images under HRTEM, some chlorites show fringe images of 21-$\AA$ (14$\AA$+7$\AA$) spacings within (001) lattice-fringe images of chlorite (14$\AA$). But brown chlorite from the black zone has high Ti and K contents suggesting that mica was the precursor of brown chlorite. Such possibility is also supported by the fact that lattice-fringe images of brown chlorite show 14-$\AA$ chlorite layers in which 10-$\AA$ mica single layer or packets are interlayered. Partial terminations from 3 mica layers to 2 chlorite layers are often observed. It, therefore, is suggested that the chlorite associated with talc ores is a hydrothermal alteration products of serpentinite, whereas the chlorites in the black alteration zone is a hydrothermal alteration product of granitic gnesis under a partial influence of serpentinite.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2299-2305
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• 2020

Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr₂O₃ formed on the outer surface of the Cr-Al alloy, and a thin Al₂O₃ layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr₂Zr.

• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.7-16
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• 1996

Partially sericitized tourmaline from a pegmatite, Black Hills, South Dakota, U.S.A., was investigated using high-resolution transmission electron microscopy (HRTEM). Muscovite occurs as the only alteration product of tourmaline, and it is developed extensively as narrow veinlets along the {110} and {100} cleavage directions of tourmaline, indicating that a cleavage-controlled alteration mechanism was dominant. Muscovite was characterized mainly as two-layer polytypes with minor stacking disorder, but tourmaline is almost free of structural defects. HRTEM images of tourmaline-muscovite interfaces revealed that the interfaces between two minerals are composed of well-defined {110} and {100} boundaries of tourmaline. The (001) of muscovite is in general parallel to the c-axis of tourmaline, but tourmaline and replacing muscovite do not show specific crystallographic orientation relationship; muscovite consists of numerous 100-1000$\AA$ thick subparallel packets, and the angles between the (001) of muscovite and (110) of tourmaline is highly variable. Al/Si ratios of both minerals suggest that tourmaline to muscovite alteration by late magnetic fluids has been facilitated by their similar Al/Si ratio in the incipient alteration stage, in that the hydration reaction with preservation of Al and Si would require only addition of K+ and H2O. Aluminous minerals other than muscovite were not characterized as the alteration products of tourmaline, indicating that tourmaline reacted directly to muscovite; the tourmaline alteration apparently occurred by the presence of residual fluids in which K+ is available and silica was not undersaturated.

• Journal of the Korean Vacuum Society
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• v.2 no.4
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• pp.501-506
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• 1993

The spatial potential distribution of electron cyclotron resonance plasma is measured as a function of tehsubstrate DC bias by Langmuir probe method. It is observed that the substrate DC bias changes the slope of the plasma potential near the subsrate, resulting in changes in flux and energy of the impinging ions across plasma $_strate boundary along themagnetric field. The effect of the substrate DC bias on the low-temperature silicon homoepitaxy (below $560^{\circ}C$) is examine dby in situ reflection high energy electron diffraction (RHEED), cross-section transmission electron microscopy (XTEM),plan-view TEM and high resolution transmision electron microscopy(HRTEM). While the polycrystalline silicon layers are grow withnegative substrate biases, the single crystaline silicon layers are grown with negative substrate biases, the singel crystalline silicon layers are grown with positive substrate biases. As the substrate bias changes form negative to positive values, the growth rate decreases. It is concluded that the control of the ion energy during plasma deposition is very important in silicon epitaxy at low temperatures below $560^{\circ}C$ by UHV-ECRCVD.VD.

• Applied Microscopy
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• v.26 no.4
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• pp.479-487
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• 1996

Thin epilayer structures of GaAs/AlAs/InGaAs, grown by Molecular Beam Epitaxy, were investigated by high resolution transmission electron microscopy, Image in the [110] zone axis was taken and compared with the calculated images. The supercell structure which contains GaAs, AlAs and InGaAs layers was designed and was employed in the image calculation with MacTempas computer program. Good agreement was shown between experimental image and a set of calculated images with varying defocus and sample thickness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.26-26
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• 2009

Vertically aligned arrays of mm-long multi-walled carbon nanotubes (MWCNTs) on Si substrates have been synthesized by water-assisted thermal chemical vapor deposition (CVD). The growth of CNTs was investigated by changing the experimental parameters such as growth temperature, growth time, gas composition, annealing time, catalyst thickness, and Al underlayer thickness. The 0.5-nm-thick Fe served as catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. We grew CNTs by adding a little amount of water vapor to enhance the activity and the lifetime of the catalyst. Al was very good at producing the nm-size catalyst particles by preventing "Ostwald ripening". The Al underlayer was varied over the range of 15~40 nm in thickness. The optimum conditions for the synthesis parameters were as follows: pressure of 95 torr, growth temperature of $815^{\circ}C$, growth for 30 min, 60 sccm Ar + 60 sccm $H_2$ + 20 sccm $C_2H_2$. The water vapor also had a great effect on the growth of CNTs. CNTs grew 5.03 mm long for 30 min with the water vapor added while CNTs were 1.73 mm long without water vapor at the same condition. As-grown CNTs were characterized by using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. High-resolution transmission electron microscopy showed that the as-grown CNTs were of ~3 graphitic walls and ~6.6 nm in diameter.