• Progress in Superconductivity
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• v.13 no.2
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• pp.127-132
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• 2011

Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.

• Textile Coloration and Finishing
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• v.17 no.2 s.81
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• pp.10-18
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• 2005

Silk fabrics mordanted with $Fe^{2+},\;Ni^{2+},\;and\;Cu^{2+}$ were dyed with the aqueous extract of Cassia tora L. seed which was known to include water soluble colorant kaempferol, one of flavonol compounds. Kaempferol can react with free radicals and chelate transition metal ions, which is thought to catalyze processes leading to the appearance of free radicals and have antioxidant activity. In relation to the coordinating and chelating mechanism of the ions with the silk protein and kaempferol, reasonable conclusions should be made on the colorant uptake and the water fastness of the fabric. The amount of the colorant on the fabric was in the order of $Fe^{2+}>Ni^{2+}>Cu^{2+}$. In case of dyeing through coordinaiton bonds between transition metal ions and silk protein and colorants, it was thought that the ions with the smaller secondary hydration shell, the higher preference to the atoms of the ligand coordinated, and the suitable bonding stability for the substitution of primarily hydrated water molecules for colorants led to the higher colorant uptake. The water fastnsess of the fabric was in the order of $Fe^{2+}>Cu^{2+}>Ni^{2+}$. It should be reasonable to choose transition metal ions with weak and strong tendency to the ionic and the coordination bond, respectively, to the carboxylate anion of the silk protein. Although further research needs to be done, the conclusions above may be generally applied to the natural dyeing through the coordination bond mechanism between transition metal ions and colorants and substrates.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.147-151
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• 2014

A boron doping process using a boron tri-bromide ($BBr_3$) as a boron source was applied to form a $p^+$ emitter layer on an n-type mono-crystalline CZ substrate. Nitrogen ($N_2$) gas as an additive of the diffusion process was varied in order to study the variations in sheet resistance and the uniformity of doped layer. The flow rate of $N_2$ gas flow was changed in the range 3 slm~10 slm. The sheet resistance uniformity however was found to be variable with the variation of the $N_2$ flow rate. The optimal flow rate for $N_2$ gas was found to be 4 slm, resulting in a sheet resistance value of $50{\Omega}/sq$ and having a uniformity of less than 10%. The process temperature was also varied in order to study its influence on the sheet resistance and minority carrier lifetimes. A higher lifetime value of $1727.72{\mu}s$ was achieved for the emitter having $51.74{\Omega}/sq$ sheet resistances. The thickness of the boron rich layer (BRL) was found to increase with the increase in the process temperature and a decrease in the sheet resistance was observed with the increase in the process temperature. Furthermore, a passivated emitter solar cell (PESC) type solar cell structure comprised of a boron doped emitter and phosphorus doped back surface field (BSF) having Ni/Cu contacts yielding 15.32% efficiency is fabricated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.30-31
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• 2006

We have fabricated SmBCO coated conductor on IBAD-MgO substrates using unique co-evaporation method. The batch type co-deposition system was specially designed and named as EDDC(evaporation using drum m dual chamber) that is possible to deposit superconducting layer with different composition ratio at low temperature of $700^{\circ}C$. In this study, we have investigated the influence of SmBCO phase composition and texture of IBAD-MgO template on the critical current density. We have changed the deposition rates of Sm, Ba and Cu during co-evaporation to examine the optimal composition ratio shown better critical current density. The composition ratio and surface morphology of SmBCO coated conductors were analyzed by the EDX and SEM, respectively. A higher critical current density was measured at superconducting phase composition ratio of Ba deficiency, Sm or Cu rich compared to the Sm1Ba2Cu3Ox stoichiometry.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.185-188
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• 1999

Biepitaxial Y$_1Ba_2Cu_3O_{7-x}$ (YBCO) and La$_{0.2}Sr_{0.8}MnO_3$ (LSMO) thin films have been prepared on SrTiO$_3$ buffer layer and MgO seed layer grown on Al$_2O_3$(11${\bar{2}}$0)substrates by dc-sputtering with hollow cylindrical targets, respectively. We charaterized Josephson properties and significantly large magnetoresistance in YBCO and LSMO films with 45$^{\circ}$ grain boundary junction, respectively. The observed working voltage (I$_cR_n$) at 77 K in grain boundary junction was below 10${\mu}$V, which is typical I$_cR_n$ value of single biepitaxial Josephson junction. The field magnetoresistance ratio (MR) of LSMO grain boundary juncoon at 77K was enhanced to 13%, which it was significant MR value with high magnetic field sensitivity at a low field of 250 Oe. These results indicate that inserting the insulating layer instead of the grain boundary layer with metallic phase can be possible to apply a new SIS Josephson junction and a novel magnetic device using spin-polarized tunneling junction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.1-9
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• 2003

In this paper, we designed a highly suppressed sidelobe ladder type RF SAW bandpass filter based on 1-port resonator, for 800 MHz mobile communication system. In order to get the highest device characteristics, we optimized some important parameters such as the electrode thickness, electrode lambda weghting of the reflectors, and static capacitance ratio. Furthermore, we fabricated the Tx and Rx. filter using optimized parameters. Implemented filters can be used in 800 MHz mobile communication system and external impedance matching circuits are not needed. RF filter was fabricated on 36$^{\circ}$LiTaO$_3$ substrates with Al-Cu (W 3 %)and mounted 3.8mm$\times$3.8mm$\times$1.5mm SMD package. Developed filters has 2.3 dB insertion loss in the 25 MHz pass-band, 33MHz with 3-dB insertion loss, stop-band rejection of 30 dB, passband ripple is less than 0.5 The power durability of the filters measured about 3.5W and the maximum temperature variation within -2$0^{\circ}C$~8$0^{\circ}C$ was 0.09 dB/$^{\circ}C$ of 3-dB insertion loss.

• Progress in Superconductivity
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• v.2 no.2
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• pp.86-91
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• 2001

Temperature dependences of the unloaded Ｑ(Ｑ$_{0}$) and the resonant frequency ( $f_{0}$) of YB $a_2$C $u_3$ $O_{7-{\delta}}$ (YBCO) microstrip ring resonators and rutile-loaded cylindrical cavity resonators were measured at low temperatures. Dc magnetron-sputtered YBCO films grown on Ce $O_2$-buffered r-cut sapphire (CbS) substrates were used fur this purpose. The surface resistances ( $R_{s}$) of YBCO films measured by both a microstrip ring resonator and a TE $01\delta$/ mode rutile-loaded cylindrical cavity resonator are compared with each other. It turned out that the values of $R_{s}$ measured by the microstrip resonator technique are comparable to those by the rutile-loaded resonator technique at temperatures lower than ~50 K. However, above 50 K, the $R_{s}$ measured by the microstrip resonator technique appeared higher according to the temperature. Our results show that the current crowding effects near the edge of a microstrip resonator become more significant at temperatures near the critical temperature.emperature.e.e.e.e.e.e.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.84-88
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• 2007

[ $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ ] (BZN), $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMN), and $Bi_2Cu_{2/3}Nb_{4/3}O_7$ (BCN) pyrochlore thin films were prepared on $Cu/Ti/SiO_2/Si$ substrates by pulsed laser deposition and the micro-structural and electrical properties were characterized for embedded capacitor applications. The BZN, BMN, and BCN films deposited at $25\;^{\circ}C$ and $150\;^{\circ}C$, respectively show smooth surface morphologies and dielectric constants of about $39\;{\sim}\;58$. The high dielectric loss of the films deposited at $150\;^{\circ}C$ compared with films deposited at $25\;^{\circ}C$ was attributed to the defects existing at interface between the films and copper electrode by an oxidation of copper bottom electrode. The leakage current densities and breakdown voltages in 200 nm thick-BMN and BZN films deposited at $150\;^{\circ}C$ are approximately $2.5\;{\times}\;10^{-8}\;A/cm^2$ at 3 V and above 10 V, respectively. Both BZN and BMN films are considered to be suitable materials for embedded capacitor applications.

• Transactions on Electrical and Electronic Materials
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• v.15 no.1
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• pp.24-27
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• 2014

In this study, the effects of Mn-doping and the electrode materials on the memory characteristics of $ZnO_xS_{1-x}$ resistive random access memory (ReRAM) devices on plastic are investigated. Compared with the undoped Al/$ZnO_xS_{1-x}$/Au and Al/$ZnO_xS_{1-x}$/Cu devices, the Mn-doped ones show a relatively higher ratio of the high resistance state (HRS) to low resistance state (LRS), and narrower resistance distributions in both states. For the $ZnO_xS_{1-x}$ devices with bottom electrodes of Cu, more stable conducting filament paths are formed near these electrodes, due to the relatively higher affinity of copper to sulfur, compared with the devices with bottom electrodes of Au, so that the distributions of the set and reset voltages get narrower. For the Al/$ZnO_xS_{1-x}$/Cu device, the ratio of the HRS to LRS is above $10^6$, and the memory characteristics are maintained for $10^4$ sec, which values are comparable to those of ReRAM devices on Si or glass substrates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.801-804
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• 2006

[ $GdAlO_3(GAO)$ ] buffer layer for $YBa_2Cu_3O_{7-{\delta}}(YBCO)$ coated superconductor wire was fabricated by sol-gel processing. Precursor solution was prepared by dissolving 1:1 stoichiometric quantaties of gadolinium nitrate hexahydrate and aluminum nitrate nonahydrate in methanol. The solution was spin-coated on $SrTiO_3(STO)$(100) single crystal substrates and heated at $1000^{\circ}C$ for 2h in wet $N_2-5%\; H_2$, atmosphere. A SEM(scanning electron microscopy) observation of the surface morphology of the GAO layer has shown that it has a faceted morphology indicating epitaxy. It was shown from x-ray diffraction(XRB) that GAO buffer layer was highly c-axis oriented epitaxial thin film with both good out-of-plane($FWHM=0.29^{\circ}$ for the (002) reflection) and in-plane ($FWHM=1.10^{\circ}$ for the {112} reflection) alignment.