• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.242-243
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• 2007

Highly transparent conducting aluminum-doped zinc oxide (AZO) thin films were deposited on Corning glass substrate using an Nd:YAG pulsed laser deposition technology. AZO thin films deposited with 650nm thickness showed the best electrical properties of the electrical resistivity of $4.6{\times}10^{-4}[{\Omega}{\cdot}cm]$, a carrier concentration of $9.3{\times}10^{20}[cm^{-3}]$, and a carrier mobility of $31[cm^2/V{\cdot}s]$. Besides, the optical transmittance spectra in visible region (200-800nm) of AZO thin films show an high average transmittance over 90%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.377-380
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• 2004

The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. GeSbTe(GST), AsSbTe(AST), SeSbTe(SST) used to phase change materials by appling electrical pulses. Thickness of ternary chalcogenide thin films have about 100nm. Upper and lower electrode were made of Al. It is compared with I-V characteristics after impress the variable pulses.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.211.1-211.1
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• 2013

We fabricate the conductive zinc oxide(ZnO) thin film using UV-enhanced atomic layer deposition. ZnO is semiconductor with a wide band gap(3.37eV) and transparent in the visible region. ZnO can be deposited with various method, such as metal organic chemical vapour deposition, magnetron sputtering and pulsed laser ablation deposition. In this experiment, ZnO thin films was deposited by atomic layer deposition using diethylzinc (DEZ) and D.I water as precursors with UV irradiation during water dosing. As a function of UV exposure time, the resistivity of ZnO thin films decreased dramatically. We were able to confirm that UV irradiation is one of the effective way to improve conductivity of ZnO thin film. The resistivity was investigated by 4 point probe. Additionally, we confirm the thin film composition is ZnO by X-ray photoelectron spectroscopy. We anticipate that this UV-enhanced ZnO thin film can be applied to electronics or photonic devices as transparent electrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.161-161
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• 2013

Two-dimensional electron gas (2DEG) has been investigated at the heterointerface between two insulating dielectric perovskite oxides, $LaAlO_3$ (LAO)/$SrTiO_3$ (STO). Properties of the 2DEG have attracted an enormous interest in condensed matter physics due to multifunctional properties such as the coexistence of ferromagnetism and superconductivity, as well as the high electron mobility. Here, we have grown $Ta_2O_5$ thin films using pulsed laser deposition on $SrTiO_3$ substrate to investigate the electric properties of the $Ta_2O_5$/STO heterointerface. Our research reveal that the non-polar $Ta_2O_5$/$TiO_2$ heterointerface favors the formation of 2DEG similar to that at the LAO/STO heterointerface. The metallic behavior was found in this heterointerface with the current about $10{\sim}100{\mu}A$ at 5 V by using conventional I-V measurements, when the $Ta_20_5$ film thickness reaches over critical thickness, $d_c{\simeq}2uc$. The finding that electrons was localized at $Ta_2O_5$/STO heterointerface have attracted to be strong and new candidate for nanoscale oxide device applications.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.263-267
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• 1998

In this study, we have fabricated in-situ multilayer $YBa_2Cu_3O_{7-\delta}$/$SrTiO_{3}$/$YBa_2Cu_3O_{7-\delta}$ ramp edge type junctions by using a metal mask and pulsed laser deposition method and studied the junction properties. The junctions showed RSJ-like I-V characteristics. The normal state junction resistance R, of $18 \omega$ was nearly constant with temperature. The dc-SQUID sensors fabricated with the junctions show a sensitivity that transfer function dV/$d\Phi$)~$22\mu$V/$\Phi_{0}$, indicating that the in-situ ramp edge type junction is potentially useful for sensor application.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.91-94
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• 1999

A new type of high-T$_c$ superconducting Josephson junctions has been prepared by Ar ion beam etching and electron beam lithography. YBa$_2Cu_3O_{7-x}$ (YBCO) films deposited on (001) SrTiO$_3$ single crystal substrate by pulsed laser deposition were patterned by Ar ion milling with photolithography. The narrow slit with a electroresist mask, about 1000 ${\AA}$ wide, was constructed over a 3 ${\sim}$ 5 ${\mu}$m bridge of a 1200-${\AA}$-thick YBCO film by electron beam lithography. The slit was then etched by the Ar ion beam to form a damaged 600-${\AA}$-thick YBCO. Thus prepared structure forms an S-N-S (YBCO - damaged YBCO - YBCO) type Josephson junctions. Those junctions exhibit RSI-like I-V characteristics at 77 K. The properties of the Josephson junctions such as I$_c$ R$_N$, and J$_c$ were characterized.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.223-228
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• 1999

We have investigated the microwave properties of a high-T$_c$. superconducting Josephson junction by Shapiro step measurements. A Josephson junction was fabricated on the bicrystal MgO substrate using pulsed laser deposition method. We have measured Shapiro steps in the I-V characteristics under the irradiation of 1.36 cm wavelength up to 45 K and found inclined current steps above 50 K. In order to understand these results, we introduced an additional resistance connected in series to RSJ model. Using this modified RSJ model, we could explain the inclined current steps as a result of superposition of the junction and an additional resistance above certain temperatures. Also, we presented the received power of the Josephson junction above 50 K.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.467-470
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• 2009

A novel 8 V DC power source with an external series-parallel connection of 50 Dye-Sensitized Solar Cells(DSSCs) has been proposed. One DSC has the optimized length to width ratio of $5.2{\times}2.6$ cm and an active area 8 $cm^2$($4.62{\times}1.73$ cm) which attained a conversion efficiency of 4.2%. From the electrochemical impedance spectroscopic analysis, it was found that the resistance elements related to the Pt electrode and electrolyte interface behave like that of diode and the series resistance corresponds to the sum of the other resistance elements. In addition, the TEMoo mode pulsed Nd:YAG laser beam is used to improve the incident photon to current efficiency(IPCE) of DSSC. From this result, this novel 8V-0.38A DC power source shows stable performance with an energy conversion efficiency of about 4.5% under 1 sun illumination(AM 1.5, Pin of 100 $mW/cm^2$).

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1868-1870
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• 2000

As a drive for an ETC (Electro-thermal Chemical) launcher, a large pulse power system of a 2.4MJ energy storage was designed, constructed and tested. The overall power system consists of eight capacitive 300kJ energy storage banks. In this paper we describe the design features, setup and operation test result of the 300kJ pulsed power module. Each capacitor bank of the 300kJ module consists of six 22kV 50kJ capacitors. A triggered vacuum switch (TVS-43) was adopted as the main pulse switch. Crowbar diode circuits, variable multi-tap inductors and energy dumping systems are connected to each high power capacitor bank via bus-bars and coaxial cables. A parallel crowbar diode stack is fabricated in coaxial structure with two series 13.5kV, 60kA avalanche diodes. The main design parameters of the 300kJ module are a maximum current of 180kA and a pulse width of 0.5 - 3ms. The electrical performances of each component and current output variations into resistive loads have been investigated.

• Journal of Sensor Science and Technology
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• v.7 no.1
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• pp.67-72
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• 1998

The crystallized CuPc and PbTe films are formed by thermal evaporation and pulsed ArF excimer laser ablation. Structural and electrical properties of thin film is observed by XRD and current-voltage(I-V) curves. From XRD analysis, both PbTe and CuPc thin films show a-axis oriented structure. For the measurement of photovoltaic effect, the transverse current-voltage curve of CuPc/Si, PbTe/Si and PbTe/CuPc/Si junctions have been analyzed in the dark and under illumination. The PbTe/CuPc/Si junction exthibits a strong photovoltaic characteristics with short circuit current($J_{sc}$) of $25.46\;mA/cm^{2}$ and open-circuit voltage($V_{oc}$) of 170 mV. Quantum efficiency and power conversion efficiency are calculated to be 15.4% and $3.46{\times}10^{-2}$, respectively. Based on the results of QE and ${\eta}$, the photocurrent process of PbTe/CuPc/Si junction can be explained as following three effective steps; photocarrier generation in the CuPc layer, carrier separation at PbTe/CuPc interface, and finally a transportation of electrons through the PbTe layer.