• Transactions of the Korean hydrogen and new energy society
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• v.11 no.1
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• pp.19-27
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• 2000

The polymer electrolyte membrane fuel cell (PEMFC) system was developed. In order to enhance the performance of membrane electrode assembly (MEA), the transfer printing method of the electrocatalyst layer on membrane was developed. The $H_2/O_2$ single cell with an electrode area of $50cm^2$ was fabricated and tested using 20 wt.% Pt/C as an electrocatalyst and the commercial and hand-made MEA such as Nafion 115, Hanwha, Dow, Flemion T and Gore Select. The 100-cell PEMFC stack with an active electrode area of $300cm^2$ was designed and fabricated using 40 wt.% Pt/C and 30 wt.% Pt-Ru/C as a cathode and anode electrocatalysts, respectively. The performance of PEMFC system was obtained to be 7kW (250A at 28V) and 3.5kW (70A at 50V) at $80^{\circ}C$ by flowing $H_2/air$ and methanol reformed fuel gas/air, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.46-52
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• 2003

In this paper, we fabricated PRT(platinum resistance thermometers) with the trimming technology using high fine laser system. U. V.(wavelength： 355nm) laser was mainly used for adjusting Pt thin films resistors to 100Ω at 0$^{\circ}C$. Internationally, the accepted A-class tolerance of temperature sensor is ${\pm}$0.06Ω at 0$^{\circ}C$. according to DIN EN 60751. The width of trimmed lines was about 10$\mu\textrm{m}$ and the best trimming conditions of Pt thin films were power : 37mW, frequency : 200Hz and bite size：1.5$\mu\textrm{m}$. And 96 resistors, fabricated by photolithography and etching process, have 79∼90Ω and 91∼102Ω as the proportion of 45.7% and 57.3%, respectively. As result of sitting Pt thin films resistors to the target value(109.73Ω at 25$^{\circ}C$), 82.3% of all resistors had the tolerance within ${\pm}$0.03Ω and the others(17.7％) were within ${\pm}$0.06Ω of A-class tolerance. The PRTs which wore fabricated in this research had excellent characteristics as follows； high accuracy, international standard TCR(temperature coefficient of resistance) value, long-term stability, wide temperature range, good linearity and repeatability, rapid response time, etc.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.83-87
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• 2004

Phase noise performance and current consumption of Radio Frequency (RF) Voltage-Controlled Oscillator (VCO) are largely dependent on the Quality (Q) factor of inductor-capacitor (LC) tank. Because the Q-factor of LC tank is determined by on-chip spiral inductor, we designed, analyzed, and modeled on-chip differential inductor to enhance differential Q-factor, reduce current consumption and save silicon area. The simulated inductance is 3.3 nH and Q-factor is 15 at 2 GHz. Self-resonance frequency is as high as 13 GHz. To verify its use to RF applications, we designed 2 GHz differential LC VCO. The measurement result of phase noise is -112 dBc/Hz at an offset frequency of 100 kHz from a 2GHz carrier frequency. Tuning range is about 500 MHz (25%), and current consumption varies from 5mA to 8.4 mA using bias control technique. Implemented in $0.35-{\mu}m$ SiGe BiCMOS technology, the VCO occupies $400\;um{\times}800\;um$ of silicon area.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.3-9
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• 1999

Pt thin film of about 7000$\AA$ thickness was deposited on the alumina substrate using DC Magnetron Sputter and the characteristics of the film for temperature sensor were investigated. When film of about 7000$\AA$ thickness was deposited at working gas pressure of $2.0{\times}10^{-3}$torr, sputtering power of 50W, substrate temperature of $350^{\circ}C$(Ts), sheet resistance(Rs), resistivity($\rho$) and temperature coefficient of resistivity(TCR) of the film were respectively 0.39$\Omega$/$\square$, 27.60$\mu\Omega$-cm and $3350 ppm/^{\circ}C$. When the film was annealed at $1000^{\circ}C$ for 240min in hydrogen ambient, Rs, $\rho$ and TCR were respectively 0.236$\Omega$/$\square$, 15.18$\mu\Omega$-cm and 3716 ppm/$3716 ppm/^{\circ}C$. When working gas of 15sccm oxygen and 100sccm Argon were used, Rs, $\rho$ and TCR were respectively 0.335$\Omega$/$\square$, 22.45$\mu\Omega$-cm and $3427 ppm/^{\circ}C$. When the film was annealed at $1000^{\circ}C$ for 240min, Rs, $\rho$and TCR were respectively 0.224/$\Omega$$\square$, 14$\mu\Omega$-cm and $3760 ppm/^{\circ}C$ and the characteristics of the film were much improved.

• Corrosion Science and Technology
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• v.23 no.1
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• pp.33-40
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• 2024

The concentration and diffusion coefficient of oxide ion vacancies in the oxide scale formed on Fe-22Cr-0.5Mn ferritic stainless steel with and without molybdenum (Mo) was measured at 800℃ by the electrochemical polarization method. After pre-oxidation for 100 h in ambient air at 800 ℃, the oxide scale on one side was completely removed with sandpaper. A YSZ plate was placed on the side where the oxide scale remained. Platinum (Pt) meshes were attached on the top of the YSZ plate and the side where the oxide scale was removed. Changes in electrical current were measured after applying an electrical potential through Pt wires welded to the Pt meshes. The results were interpreted by solving the diffusion equation. The diffusion coefficient and concentration of oxide ion vacancy decreased by 30% and 70% in the specimen with Mo, respectively, compared to the specimen without Mo. The oxide ion vacancy concentration of chromia decreased due to the addition of Mo.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.816-819
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• 1995

(Ba$_{1-x}$ , Sr$_{x}$)TiO/$_3$thin films on Pt/Ti/SiO$_2$/Si substrates were prepared by LP MOCVD(Low Pressure Metal-Organic Chemical Vapor Deposition). The crystalinity of BST deposit had a (100) preferred orientation with increasing deposition temperature due to surface diffusion. BST films deposited at 90$0^{\circ}C$ showed a dielectric constant of 365 and a dissipation factor of 0.052 at a frequency of 100kHz. The chance of capacitance of the films with applied voltage was small, showing paraelectric properties. BST film deposited at 90$0^{\circ}C$ had a charge storage density of 60 fc/${\mu}{\textrm}{m}$$^2$at a field of 0.2MV/cm and the leakage current density of 20 nA/$\textrm{cm}^2$ at a field of 0.15 MV/cm.cm.

• Journal of Sensor Science and Technology
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• v.8 no.4
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• pp.327-332
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• 1999

Catalytic combustion type gas sensors were fabricated by using noble metal(Pt and Pd) added ${\gamma}-Al_2O_3$ powder with specific surface area of $200\;m^2/g$. The fabricated sensor showed power consumption of 500 mW at the operating voltage of 1.75 V and high sensitivity of about 120 mV for butane, methane, or propane 100%LEL, respectively. The sensor properties also showed good linearity to hydrocarbon gas concentration variation, reproductivity and stability for relative humidity variation. And it showed high stability in butane ambient for 100 days.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.199-203
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• 2000

$Ta_2_O5$ and $Sr_0.8Bi_2.4Ta_2O_9$ films were deposited on p-type Si(100) substrates by a rf-magnetron sputtering and the metal organic decomposition (MOD), respectively.The electrical characteristics of the $Pt/SBT/Ta_2O_5/Si$ structure were obtained as the functions of $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering and $Ta_2_O5$ thickness. And to certify the role of $Ta_2_O5$ as a buffer layer, the electrical characteristics of $Pt/SBT/Ta_2O_5/Si$ were compared. $Pt/SBT/Ta_2O_5/Si$ capacitor with 20% $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering did now show typical C-V curve of metal/ferroelectric/insulator/semiconductor (MFIS) structure. The capacitor with 20% $O_2$ gas flow ratio during the $Ta_2_O5$ sputtering had the largest memory window. And the memory window was decreased as the $Ta_2_O5$ gas flow ratio during the $Ta_2_O5$ sputtering was increased to 40%, 60%. In the C-V characteristics of the $Pt/SBT/Ta_2O_5/Si$ capacitors with the different $Ta_2_O5$ thickness, the capacitor with 26nm thickness of $Ta_2_O5$ had the largest memory window. The C-V and leakage current characteristics of the Pt/SBT/Si structure were worse than those of $Pt/SBT/Ta_2O_5/Si$ structure. These results and Auger electron spectroscopy (AES) measurement showed that $Ta_2_O5$ films as a buffer layer tool a role to prevent from the formation of intermediate phase and interdiffusion between SBT and Si.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.319-322
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• 2003

To match the charge induced by the insulators $CeO_2$ with the remanent polarization of ferro electric SBT thin films, areas of Pt/SBT/Pt (MFM) and those of $Pt/CeO_2/Si$ (MIS) capacitors were ind ependently designed. The area $S_M$ of MIS capacitors to the area $S_F$ of MFM capacitors were varied from 1 to 10, 15, and 20. Top electrode Pt and SBT layers were etched with for various area ratios of $S_M\;/\;S_F$. Bottom electrode Pt and $CeO_2$ layers were respectively deposited by do and rf sputtering in-situ process. SBT thin film were prepared by the metal orgnic decomposition (MOD) technique. $Pt(100nm)/SBT(350nm)/Pt(300nm)/CeO_2(40nm)/p-Si$ (MFMIS) gate structures have been fabricated with the various $S_M\;/\;S_F$ ratios using inductively coupled plasma reactive ion etching (ICP-RIE). The leakage current density of MFMIS gate structures were improved to $6.32{\times}10^{-7}\;A/cm^2$ at the applied gate voltage of 10 V. It is shown that in the memory window increase with the area ratio $S_M\;/\;S_F$ of the MFMIS structures and a larger memory window of 3 V can be obtained for a voltage sweep of ${\pm}9\;V$ for MFMIS structures with an area ratio $S_M\;/\;S_F\;=\;6$ than that of 0.9 V of MFS at the same applied voltage. The maximum memory windows of MFMIS structures were 2.28 V, 3.35 V, and 3.7 V with the are a ratios 1, 2, and 6 at the applied gate voltage of 11 V, respectively. It is concluded that ferroelectric gate capacitors of MFMIS are good candidates for nondestructive readout-nonvolatile memories.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.10
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• pp.1514-1519
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• 2005

This study was performed to investigate the effects of Porphyra tenera (PT) on cytotoxicity and quinone reductase (QR) activity in the cancer cells. PT was extracted with methanol and further fractionated into five different types: hexane (PTMH), ethyl-ether (PTMEE), ethylacetate (PTMEA) butanol (PTMB) and aquous (PTMA) partition layers. We determined the cytotoxic effect of these layers on C6, HepG2, MCF-7, and HT-29 cell lines by MTT assay. Among the various fractions, hexane (PTMH) of PT showed the strongest cytotoxic effect on C6, HepG2 and MCF-7 cell lines. PTMH displayed very low level of cytotoxicity at the lower concentration levels and at 300 $\mu$g/mL. PTMH resulted in 87.5$\%$ growth inhibition on C6 cell 70 $\%$ on the HepG2 cell and 89$\%$ on the MCF-7 cell, which were significantly high compared to other fractions. A 400 $\mu$g/mL PTMH concentration level, 99$\%$, 94.5$\%$ and 99$\%$ of cell growth inhibition were resulted on the same cell lines. On HT-29 cell line, both hexane (PTMH) and aqueous (PTMA) fraction of PT showed cytotoxic effects, but the Percentage was not as high as previous results tested on other cell lines such as C6 HepG2 and MCF-7 cell lines. Also, we observed quinone reductase (QR) inducing-effects in all fractions of PT on HepG2 cells. The QR inducing effects of the PTMH on HepG2 cells at 150 $\mu$g/mL concentration was 6.6 times higher than the control. Although further studies are needed, the present work suggests that PT was a potential to be used as a chemopreventive.