• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.6
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• pp.546-549
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• 2007

As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost. Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique. 100 nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $1\;{\mu}m-thick$ SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-5%W substrate. Critical current of 90 A/cm was obtained for the SmBCO coated conductors.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.32-36
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• 2006

Simplification of the buffer architecture in the fabrication of coated conductors is required because the deposition of multi-layers leads to a longer production time and a higher cost of coated conductors. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique. l00nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $0.4{\mu}m$-thick SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-W substrate. Critical current of $55.4 A/cm^2$ was obtained for the SmBCO coated conductors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.363-368
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• 2010

In this work, electrochemiluminescence (ECL) cell using nanocrysralline $TiO_2$ electrode and Ru(II) complex (Ru${(bpy)_3}^{2+}$) is fabricated for low-cost high-efficient energy conversion device application. The nanocrysrallme $TiO_2$ layer (${\sim}10{\mu}m$ thickness) with large surface area (${\sim}360m^2$/g) can largely inject electrons from nanoporous $TiO_2$ electrode and allows the oxidation/reduction of Ru(II) complex in the nanopores. The cell structure is composed of a glass/ F-doped $SnO_2$(FTO)/ porous $TiO_2$/ Ru(II) complex in acetonitrile/ FTO/ glass. The nanocrysralline $TiO_2$ layer is prepared using sol-gel combustion method. The ECL efficiency of the cell consisting of the porous $TiO_2$ layers was 250 cd/W, which was higher than that consisting of only FTO electrode (50cd/W). The nanoporous $TiO_2$ layers wwas effective for increasine ECL intensities.

• ETRI Journal
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• v.25 no.2
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• pp.65-72
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• 2003

To achieve cost and size reductions, we developed a low cost manufacturing technology for RF substrates and a high performance passive process technology for RF integrated passive devices (IPDs). The fabricated substrate is a conventional 6" Si wafer with a 25${\mu}m$ thick $SiO_2$ surface. This substrate showed a very good insertion loss of 0.03 dB/mm at 4 GHz, including the conductive metal loss, with a 50 ${\Omega}$ coplanar transmission line (W=50${\mu}m$, G=20${\mu}m$). Using benzo cyclo butene (BCB) interlayers and a 10 ${\mu}m$ Cu plating process, we made high Q rectangular and circular spiral inductors on Si that had record maximum quality factors of more than 100. The fabricated inductor library showed a maximum quality factor range of 30-120, depending on geometrical parameters and inductance values of 0.35-35 nH. We also fabricated small RF IPDs on a thick oxide Si substrate for use in handheld phone applications, such as antenna switch modules or front end modules, and high-speed wireless LAN applications. The chip sizes of the wafer-level-packaged RF IPDs and wire-bondable RF IPDs were 1.0-1.5$mm^2$ and 0.8-1.0$mm^2$, respectively. They showed very good insertion loss and RF performances. These substrate and passive process technologies will be widely utilized in hand-held RF modules and systems requiring low cost solutions and strict volumetric efficiencies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.180-181
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• 2006

As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique 100nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $0.4{\mu}m$-thick SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-W substrate. Critical current of 118A/$cm^2$ was obtained for the SmBCO coated conductors.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.18-21
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• 2011

In this work, the yttrium oxide($Y_2O_3$) thin films as the buffer layer were prepared by the simple solution coating and reel-to-reel process on an unpolished metal tape substrate. The $Y_2O_3$ thin films were successfully synthesized by the hydrolysis of yttrium acetate. We have studied the improvement of surface roughness with the concentration of solution(0.1 M, 0.4 M, M) and the number of coatings. The planarization by solution coating process is simple in comparison with the existing polishing process, and it is eco-friendly, and has the benefits of low cost process. The thickness of $Y_2O_3$ films was increased with the $Y_2O_3$ concentration in the solution, and the surface became smoother with the number of coating cycles. Using this process, we have achieved 1.2 nm RMS roughness from a starting roughness of over 31 nm on 25 ${\mu}m^2$ area.

• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1707-1718
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• 1996

Given a signal net N=s, 1,...,n to be the set of nodes, with s the source and the remaining nodes sinks, an MRDPT (minimum-cost rectilinear Steiner distance -preserving tree) has the property that the length of every source to sink path is equal to the rectilinear distance between the source and sink. The minimum- cost rectilinear Steiner distance-preserving tree minimizes the total wore length while maintaining minimal source to sink length. Recently, some heuristic algorithms have been proposed for the problem offending the MRDPT. In this paper, we investigate an optimal structure on the MRDPT and present a theoretical breakthrough which shows that the min-cost flow formulation leads to an efficient O(n2logm)2) time algorithm. A more practical extension is also in vestigated along with interesting open problems.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.434-436
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• 2013

Ga-doped ZnO (GZO) was substitutes of the SnO2:F films on soda lime glass substrate in the photovoltaic devices such as CIGS, CdTe and DSSC due to good properties and low cost. However, it was reported that the electrical resistivity of GZO is unstable above $300^{\circ}C$ in air atmosphere. To improve thermal stability of GZO thin films at high temperature above $300^{\circ}C$ an $TiO_2$ thin film was deposited on the top of GZO thin films as a barrier layer by Pulsed Laser Deposition (PLD) method. $TiO_2$ thin films were deposited at various thicknesses from 25 nm to 100 nm. Subsequently, these films were annealed at temperature of $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$ in air atmosphere for 20 min. The XRD measurement results showed all the films had a preferentially oriented ( 0 0 2 ) peak, and the intensity of ( 0 0 2 ) peak nearly did not change both GZO (300 nm) single layer and $TiO_2$ (50 nm)/GZO (300 nm) double layer. The resistivity of GZO (300 nm) single layer increased from $7.6{\times}10^{-4}{\Omega}m$ (RT) to $7.7{\times}10^{-2}{\Omega}m$ ($500^{\circ}C$). However, in the case of the $TiO_2$ (50 nm)/GZO (300 nm) double layer, resistivity showed small change from $7.9{\times}10^{-4}{\Omega}m$ (RT) to $5.2{\times}10^{-3}{\Omega}m$ ($500^{\circ}C$). Meanwhile, the average transmittance of all the films exceeded 80% in the visible spectrum, which suggests that these films will be suitable for photovoltaic devices.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.447-454
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• 2017

A new amperometric biosensor has been developed for the detection of hydrogen peroxide ($H_2O_2$). The sensor was fabricated through the one-step deposition of a biocomposite layer onto a glassy carbon electrode at neutral pH. The biocomposite, as a $H_2O_2$ sensing element, was prepared by the electrochemical deposition of a homogeneous mixture of graphene oxide, aniline, and horseradish peroxidase. The experimental results clearly demonstrated of that the sensor possessed high electrocatalytic activity and responded to $H_2O_2$ with a stable and rapid manners. Scanning electron microscopy, cyclic voltammetry, and amperometry were performed to optimize the characteristics of the sensor and to evaluate its sensing chemistry. The sensor exhibited a linear response to $H_2O_2$ in the range of 10 to $500{\mu}M$ concentrations, and its detection limit was calculated to be $1.3{\mu}M$. The proposed sensing-chemistry strategy and the sensor format were simple, cost-effective, and feasible for analysis of "food-grade $H_2O_2$" in food samples.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.16-16
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• 2002

The presently commercialized lithium-ion batteries use layer structured LiCoO₂ cathodes. Because of the high cost and toxicity of cobalt, an intensive search for new cathode materials has been underway in recent years. Recently, a concept of a one-to-one solid state mixture of LiNO₂ and LiMnO₂, i.e., Li[Ni/sub 0.5/Mn/sub 0.5/]O₂, was adopted by Ohzuku and Makimura to overcome the disadvantage of LiNiO₂ and LiMnO₂. Li[Ni/sub 0.5/Mn/sub 0.5/]O₂ has the -NaFeO₂ structure, which is characteristic of the layered LiCoO₂ and LiNiO₂ structures and shows excellent cycleability with no indication of spinel formation during electrochemical cycling. Layered Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials with high homogeneity and crystallinity were synthesized using a mechanical alloying method. The Li[Ni/sub 0.475/Co/sub 0.05/Mn/sub 0.475/]O₂ electrode delivers a high discharge capacity of 187 mAh/g between 2.8 and 4.6 V at a high current density of 0.3 mA/㎠(30 mA/g) with excellent cycleability. The charge/discharge and differential capacity vs. voltage studies of the Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials showed only one redox peak up to 50 cycles, which indicates that structural phase transitions are not occurred during electrochemical cycling. The magnitude of the diffusion coefficients of lithium ions for Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂(x = 0.5 and 0.475) are around 10/sup -9/ ㎠/s measured by the galvanostatic intermittent titration technique (GITT).