• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.246-246
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• 2010

As the trench width in the interconnect technology decreases down to nano-scale below 50 nm, superconformal gap-filling process of Cu becomes very critical for Cu interconnect. Obtaining superconfomral gap-filling of Cu in the nano-scale trench or via hole using MOCVD is essential to control nucleation and growth of Cu. Therefore, nucleation of Cu must be suppressed near the entrance surface of the trench while Cu layer nucleates and grows at the bottom of the trench. In this study, suppression of Cu nucleation was achieved by treating the Ru barrier metal surface with capacitively coupled hydrogen plasma. Effect of hydrogen plasma pretreatment on Cu nucleation was investigated during MOCVD on atomic-layer deposited (ALD)-Ru barrier surface. It was found that the nucleation and growth of Cu was affected by hydrogen plasma treatment condition. In particular, as the plasma pretreatment time and electrode power increased, Cu nucleation was inhibited. Experimental data suggests that hydrogen atoms from the plasma was implanted onto the Ru surface, which resulted in suppression of Cu nucleation owing to prevention of adsorption of Cu precursor molecules. Due to the hydrogen plasma treatment of the trench on Ru barrier surface, the suppression of Cu nucleation near the entrance of the trenches was achieved and then led to the superconformal gap filling of the nano-scale trenches. In the case for without hydrogen plasma treatments, however, over-grown Cu covered the whole entrance of nano-scale trenches. Detailed mechanism of nucleation suppression and resulting in nano-scale superconformal gap-filling of Cu will be discussed in detail.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.927-933
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• 1997

The effects of carbon black on the electrodes performance and on the structure of the catalyst layer in Raney nickel hydrogen electrodes for alkaline fuel cells were investigated by using electrochemical and nitrogen adsorption methods. The optimum content of carbon black in the catalyst layer of Raney nickel hydrogen electrode was 2wt%. The limiting current density was increased by the addition of carbon black due to the enlargement of gas-liquid interface area. The rate determining step at the limiting current density was supposed to be a step where hydrogen dissolves at gas-liquid interfaces.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.31-37
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• 2017

A synergistic effect was observed in the combination of nitrite and ethanolamines. Ethanolamine is one of the representative organic corrosion inhibitors and can be categorized as adsorption type. However, nitrosamines can form when amines mix with sodium nitrite. Since nitrosamine is a carcinogen, the co-addition of nitrite and ethanolamine will be not practical, and thus, a non-toxic combination of inhibitors shall be needed. In order to maximize the effect of monoethanolamine, we focused on the addition of molybdate. Molybdate has been used to alternate the addition of chromate, but it showed insufficient oxidizing power relative to corrosion inhibitors. This work evaluated the synergistic effect of the co-addition of molybdate and monoethanolamine, and its corrosion mechanism was elucidated. A high concentration of molybdate or monoethanolamine was needed to inhibit the corrosion of ductile cast iron in tap water, but in the case of the co-addition of molybdate and monoethanolamine, a synergistic effect was observed. This synergistic effect could be attributed to the molybdate that partly oxidizes the metallic surface and the monoethanolamine that is simultaneously adsorbed on the graphite surface. This adsorbed layer then acts as the barrier layer that mitigates galvanic corrosion between the graphite and the matrix.

• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.741-748
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• 2016

Laboratory scale model was constructed for open-cut riverbed infiltration experiment and four kinds of media were selected, medium sand, sand, volcanic rock, and gravel, for the experiment. Hydraulic conductivity for each medium and flow rate from the collecting pipe with functional screen were estimated from the experiment. Modified hydraulic conductivity scenarios considering turbid water (30~50 NTU) were applied in Visual MODFLOW modeling to analyze the effects of turbid water on the flow rate. Twenty-two scenarios were generated considering prticles in turbid water and applied to each medium cases in MODFLOW modeling. The minimum error was occurred when the gravel medium had 20% less hydraulic conductivities for the third layer-depth from the top and clay particles in turbid water might play a role in adsorption process to the surface of volcanic rock (2~5 mm). For medium sand case the error was also quite small when the mediumhas 5% less hydraulic conductivities for the second layer-depth from the top.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.145-146
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• 2007

Dye-Sensitized Solar Cell Solar cells(DSSC) were appeared for overcoming global environmental problems and lack of fossil fuel problems. And it is one of study field that is getting into the spotlight lately because manufacturing method is more simple and inexpensive than existing silicon solar cells. Oxide semiconductor is used for adsorption of dye and electron transfer in DSSC study, and $TiO_2$ is used most usually. Overall light conversion efficiency is changed by several elements such as $TiO_2$ particle size and structure, pore size and shape. In this study, we report the solar cell performance of titania$(TiO_2)$ film electrodes with various particle sizes. $TiO_2$ particle size was 16 nm, 25 nm, and mixture of 16nm and 25 nm, and manufactured using Doctor blade method. When applied each $TiO_2$ film to DSSC, the best efficiency was found at 16nm of $TiO_2$ particle. 16nm of $TiO_2$ particle has the highest efficiency compared to the others, because particles with smaller diameters would adsorb more dye due to larger surface area. And in case of the mixture of 16nm and 25 nm, the surface area was smaller than expected. It is estimated that double layer is adsorbed a large amount of chemisorbed dye and improved light scattering leading due to efficiency concentration light than mono layer.

• Geomechanics and Engineering
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• v.7 no.2
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• pp.183-200
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• 2014

The expansivity of clayey soils is a complicated phenomenon which may affect the stability of geotechnical structures and geo-environmental projects. In all common factors for the monitoring of soil expansion, less attention is given to anion type of pore space solutions. Therefore, this paper is concerned with the impact of various concentrations of different inorganic salts including NaCl, $Na_2SO_4$, and $Na_2CO_3$ on the macro and microstructure behavior of the expandable smectite clay. Comparison of the responses of the smectite/NaCl and smectite/$Na_2SO_4$ mixtures indicates that the effect of anion valance on the soil engineering properties is not very pronounced, regardless of the electrolyte concentration. However, at presence of carbonate as potential determining ions (PDIs) the swelling power increases up to 1.5 times compared to sulfate or chloride ions. The samples with $Na_2CO_3$ are also more deformable and show lower osmotic compressibility than the other mixtures. This demonstrates that the barrier performance of smectite greatly decreases in case of anions with the non-specific adsorption (e.g., $Cl^-$ and $SO{_4}^{2-}$) as the salinity of solution increases. Based on the results of the X-ray diffraction and sedimentation tests, the high soil volumetric changes upon exposure to carbonate is attributed to an increase in the repulsive forces between smectite basic unit layers due to the PDI effect of $CO{_3}^{2-}$ and increasing the pH level which enhance the buffering capacity of smectite. The study concluded that the nature of anion through its influence on the re-arrangement of soil microstructure and osmotic phenomena governs the hydro-mechanical parameters of expansive clays. It seems not coinciding with the double layer theory of the Gouy-Chapman double layer model.

• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.900-909
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• 2018

A $ZnO/TiO_2$ photocatalyst decorated with PbS quantum dots (QDs) was synthesized to achieve high photocatalytic efficiency for the decomposition of dye in aqueous media. A $TiO_2$ porous layer, as a precursor photocatalyst, was fabricated using micro-arc oxidation, and exhibited irregular porous cells with anatase and rutile crystalline structures. Then, a ZnO-deposited $TiO_2$ catalyst was fabricated using a zinc acetate solution, and PbS QDs were uniformly deposited on the surface of the $ZnO/TiO_2$ photocatalyst using the successive ionic layer adsorption and reaction (SILAR) technique. For the PbS $QDs/ZnO/TiO_2$ photocatalyst, ZnO and PbS nanoparticles are uniformly precipitated on the $TiO_2$ surface. However, the diameters of the PbS particles were very fine, and their shape and distribution were relatively more homogeneous compared to the ZnO particles on the $TiO_2$ surface. The PbS QDs on the $TiO_2$ surface can induce changes in band gap energy due to the quantum confinement effect. The effective band gap of the PbS QDs was calculated to be 1.43 eV. To evaluate their photocatalytic properties, Aniline blue decomposition tests were performed. The presence of ZnO and PbS nanoparticles on the $TiO_2$ catalysts enhanced photoactivity by improving the absorption of visible light. The PbS $QDs/ZnO/TiO_2$ heterojunction photocatalyst showed a higher Aniline blue decomposition rate and photocatalytic activity, due to the quantum size effect of the PbS nanoparticles, and the more efficient transport of charge carriers.

• Bulletin of the Korean Chemical Society
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• v.18 no.8
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• pp.831-840
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• 1997

Core/shell structured composite metal oxides of Fe2O3/MgO were prepared by thermal decomposition of Fe(acac)3 adsorbed on the surface of MgO cores. The morphology of the composites conformed to that of the MgO used as the cores. Broad powder X-ray diffraction peaks shifted toward larger d, large BET surface area (∼350 m2/g), and the size of crystalline domains in nano range (4 nm), all corroborate to the nanocrystallinity of the Fe2O3/MgO composite which was prepared by using nanocrystalline MgO as the core. By use of microcrystalline MgO as the core, microcrystalline Fe2O3/MgO composite was prepared, and it had small BET surface area of less than 35 m2/g. AFM measurements on nanocrystalline Fe2O3/MgO showed a collection of spherical aggregates (∼80 nm dia) with a very rough surface. On the contrary, microcrystalline Fe2O3/MgO was a collection of plate-like flat crystallites with a smooth surface. The nitrogen adsorption-desorption behavior indicated that microcrystalline Fe2O3/MgO was nonporous, whereas nanocrystalline Fe2O3/MgO was mesoporous. Bimodal distribution of the pore size became unimodal as the layer of Fe2O3 was applied to nanocrystalline MgO. The macropores in a wide distribution which the nanocrystalline MgO had were absent in the nanocrystalline Fe2O3/MgO. The decomposition of CCl4 was largily enhanced by the overlayer of Fe2O3 on nanocrystalline MgO making the reaction between nanocrystalline Fe2O3/MgO and CCl4 be nearly stoichiometric. The reaction products were environmentally benign MgCl2 and CO2. Such an enhancement was not attainable with the microcrystalline samples. Even for the nanocrystalline MgO, the enhancement was not attained, if not with the Fe2O3 layer. Without the layer of Fe2O3, it was observed that the nanocrystalline domain of the MgO transformed into microcrystalline one as the decomposition of CCl4 proceeded on its surface. It appeared that the layer of Fe2O3 on the particles of nanocrystalline Fe2O3/MgO blocked the transformation of the nanocrystalline domain into microcrystalline one. Therefore, in order to attain stoichiometric reaction between CCl4 and Fe2O3/MgO core/shell structured composite metal oxide, the morphology of the core MgO has to be nanocrystalline, and also the nanocrystalline domains has to be sustained until the core was exhausted into MgCl2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.660-666
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• 2010

Carbon aerogels are promising materials as electrodes for electrical double layer capacitors (EDLCs). An optimum process is presented for synthesis of nanoporous carbon aerogels via pyrolyzing resorcinol-formaldehyde (RF) organic aerogels, which could be cost-effectively manufactured from RF wet gels. The major reactions between resorcinol and formaldehyde include an addition reaction to form hydroxymethyl derivatives ($-CH_2OH$), and then a condensation reaction of the hydroxymethyl derivatives ($-CH_2-$)- and methylene ether ($-CH_2OCH_2-$) bridged compounds. The textural properties of carbon aerogels obtained were characterized by nitrogen adsorption/desorption analysis and SEM and TEM. The application of the resultant carbon for electrodes of electric double layers capacitor (EDLC) in organic TEABF4/ACN electrolyte indicated that the ESR, as low as 55 $m{\Omega}$, was smaller than for commercially activated carbons. And EDLC with carbon Aerogel electrodes has an excellent stable more than for commercially activated carbons.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.30-36
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• 2002

A 0.19 hectare natural-type wetland for stream water treatment demonstration was constructed and planted with cattails from April 2001 to May 2001. Part of its bottom surfaces adjacent to levees have a variety of slope of 1 : 4~1 : 15. Two small open water areas were installed, in which emergent plants could not grow. Removal of nutrients from stream waters was a major objective of the wetland. Waters of Sinyang Stream flowing into Kohung Estuarine Lake were pumped and funneled into the wetland. The lake had been formed by a salt marsh reclamation project and was located southern coastal region of Korean Peninsula. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow and outflow averaged $120.4m^3/day$ and $112.1m^3/day$, respectively. Hydraulic retention time was about 3.1 days. Average total phosphorous concentration of influent and effluent was $0.19mg/{\ell}$ and $0.075mg/{\ell}$, respectively. Total phosphorous loading rate of inflow and outflow averaged $12.05mg\;m^{-2}\;day^{-1}$ and $4.44mg\;m^{-2}\;day^{-1}$, respectively. Average total phosphorous removal rate in the wetland was $7.61mg\;m^{-2}\;day^{-1}$. Seasonal changes of phosphorous retention rates were observed. The wetland acted as effective phosphorous sinks in the initial stage of the constructed wetland.