• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1808-1810
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• 2004

This paper describes the discharge characteristics of liquid $SF_6$ (-41$[^{\circ}]$, 1.7[atm]) and $LN_2$ for plane to plane, needle to plane, plane to needle and sphere to plane electrode with gap variations from 1[mm] to 12[mm]. From this result, the breakdown voltage was increased with increasing gap length. Especially, the formation of bubbles by evaporation was observed in spite of non-applying voltage source. A corona is created of the applying voltage from the bubbles on the electrodes applied voltage. We consider it equal mechanism of corona as void exists in solid insulator. The results of liquid $SF_6$ and $LN_2$ discharge characteristics were caused by bubble formed evaporation and applied electric field voltage. Corona was happened to weak bubble and was proceed to new bubble breakdown.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.133-140
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• 2004

We carried out anodic aluminum oxide (AAO) on a Si and a sapphire substrate. For anodic oxidation of Al two types of specimens prepared were Al(0.5 $\mu\textrm{m}$)!Si and Al(0.5 $\mu\textrm{m}$)/Ti(0.1 $\mu\textrm{m}$)$SiO_2$(0.1 $\mu\textrm{m}$)/GaN(2 $\mu\textrm{m}$)/Sapphire. Surface morphology of Al film was analyzed depending on the deposition methods such as sputtering, thermal evaporation, and electron beam evaporation. Without conventional electron lithography, we obtained ordered nano-pattern of porous alumina by in- situ process. Electropolishing of Al layer was carried out to improve the surface morphology and evaluated. Two step anodizing was adopted for ordered regular array of AAO formation. The applied electric voltage was 40 V and oxalic acid was used as an electrolyte. The reference electrode was graphite. Through the optimization of process parameters such as electrolyte concentration, temperature, and process time, a regular array of AAO was formed on Si and sapphire substrate. In case of Si substrate the diameter of pore and distance between pores was 50 and 100 nm, respectively. In case of sapphire substrate, the diameter of pore and distance between pores was 40 and 80 nm, respectively

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.69.2-69.2
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• 2010

Recently, bulk hetero-junction cells have been extensively studied by many researchers. Most of these cells were fabricated by spin coater. However, the spin coating process is not favorable to the large-scaled industry because it is not compatible with roll-to-roll process. One of the alternative methods is Doctor blading. In this study, we fabricated large OPV cells having total area of $100cm^2$. The buffer layer was Poly-(3,4-ethylenedioxythiophene) : poly-(styrenesulfonate) aqueous dispersion (PEDOT:PSS) and the active material is poly (3-hexythiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend in the solvent of Chlorobenzene. All of the organic layers were coated by dragging the blade with a speed of 5~20 mm/s on the stage with a temperature of $50^{\circ}C$. As-bladed PEDOT:PSS layer was baked at $120^{\circ}C$ for 10 minutes to eliminate the water. The cell structure is patterned ITO substrate/PEDOT:PSS/P3HT:PCBM/LiF/Al. The topmost electrode, LiF/Al, was deposited by thermal evaporation. After depositing electrode, and the cell was annealed at $150^{\circ}C$ for 30 minutes. The measured ISC, VOC, fill factor, and PCE were 2.95 A, 5.86 V, 0.32, and 0.78%, respectively. PCE was quite low but the large active area could be obtained successfully.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.362-365
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• 2002

Hf thin films were deposited on bottom metal using a RF magnetron sputtering method followed by oxidation and annealing in O$_2$ and N$_2$ ambient, respectively. Various top metal electrodes (i.e., Al, Au, and Cu) were deposited by evaporation, and their roles on physical and electrical properties were investigated. Using the XRD, SEM and AFM techniques, we confirmed that the grain size of HfO$_2$ thin films enlarges as a function of oxidation temperature, increasing dielectric constant. However, other electrical properties (e.g., tan) deteriorateas a consequence. The dielectric constant and tan of HfO$_2$ thin films oxidized at 500 $^{\circ}C$ were 17-25 and 3${\times}$10-3 - 2x10-2, respectively, in the frequency range of 1 Hz to 1 MHz. The leakage current density was less than 1${\times}$10-8A/cm2 up to 0.7 MV/cm. In addition, electrical properties of HfO$_2$ thin films (e.g., the dielectric constant, leakage current and tan $\delta$) depend on top metal electrode. We showed that Al top metal electrode results in the best result.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.701-706
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• 2013

We have focused on the conversion efficiency of CIGS thin film solar cell prepared by co-evaporation method as well as the optimization of process condition. The total thickness of back electrode was fixed at 1 ${\mu}m$ and the structural, electric and optical properties of CIGS thin film were investigated by varying the thickness of Mo:Na bottom layer from 0 to 500 nm. From the experimental results, the content of Na was appeared as 0.28 atomic percent when the thickness of Mo:Na layer was 300 nm with compactly densified plate-shape surface morphology. From the XRD measurements, (112) plane was the strongest preferential orientation together with secondary (220) and (204) planes affecting to the crystallization. The lowest roughness and resistivity were 2.67 nm and 3.9 ${\Omega}{\cdot}cm$, respectively. In addition, very high carrier density and hole mobility were recorded. From the optimization of Mo:Na layer, we have achieved the conversion efficiency of 9.59 percent.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1869-1873
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• 2008

In this work, to make it possible to generate glow discharge in atmospheric pressure condition with relatively high and wide electric field, micro channel reactor is proposed. Si DRIE and Cr deposition by Ebeam evaporation is used to make channel and bottom electrode layer. Upper electrode is made from ITO glass to visualize discharge within micro channel. Fabricated reactor is verified by generating uniform glow plasma with N2 / He gases each as working fluid. The range of gas electric field to generate glow plasma is from about 200 V/cm and upper limit is not observed in tested condition of up to 150 kV/cm. This data shows that micro channel plasma reactor is more versatile. Indirect estimation of electron temperature in this reactor can be inferred that the electron temperature within glow discharge in micro reactor lies $0{\sim}2eV$. This research demonstrates that the reactor is appropriate in application that needs to maintain low temperature condition during chemical process.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.47-51
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• 2008

The Al:Au double-layer metal electrode for use in transparent, dual emission of organic light-emitting diode (OLED) was fabricated. The electrode of Al:Au metals with various thicknesses was deposited by the vacuum thermal evaporation technique. For Al thickness of 1 nm, a bottom luminance of $4880\;cd/m^2$ was observed at 8 V. Otherwise, top luminance of $2020\;cd/m^2$ were observed at 8 V. In addition, the threshold voltages of the electrodes were 2.2 V. It was forward that the inserting 1 nm Al between LiF and Au enhanced electron injection with tunneling effect.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.800-807
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• 2005

Cathode material, $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$, for low temperature SOFC was prepared by the Glycine-Nitrate synthesis Process (GNP). Characteristics of the synthesized powders were studied with controlling the pH of a precursor solution. Highly acidic precursor solution increased a perovskite forming temperature. It is considered that Ba and Sr cannot complex by carboxylic acid group of glycine, because under highly acidic condition the caboxylic group mainly combined with H+ insead of alkaline earth cations. A lack of bond between cations and glycine resulted in selective precipitation of the elements during evaporation of the precursor solution. In case of using precursor solution with pH %2\~3$, a single perovskite phase was obtained at $1000^{\circ}C$. Polarization resistance of $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ was measured by AC impedance spectroscopy from the two electrode symmetric cell. Area specific resistance of the $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ air electrode at $500^{\circ}C\;and\;600^{\circ}C$ were $0.96{\Omega}{\cdot}cm^2\;and\;0.16{\Omega}{\cdot}cm^2$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.467-468
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• 2006

We report on the fabrication of P3HT-based thin-film transistors (TFT) that consist of indium-zinc-oxide (IZO), PVP (poly-vinyl phenol), and Ni for the source-drain (S/D) electrode, gate dielectric, and gate electrode, respectively. The IZO S/D electrodes of which the work function is well matched to that of P3HT were deposited on a P3HT channel by thermal evaporation of IZO and showed a moderately low but still effective transmittance of ~25% in the visible range along with a good sheet resistance of ${\sim}60{\Omega}/{\square}$. The maximum saturation current of our P3HT-based TFT was about $15{\mu}A$ at a gate bias of -40V showing a high field effect mobility of $0.05cm^2/Vs$ in the dark, and the on/off current ratio of our TFT was about $5{\times}10^5$. It is concluded that jointly adopting IZO for the S/D electrode and PVP for gate dielectric realizes a high-quality P3HT-based TFT.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.335-338
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• 2004

In this paper the experiments of insulation characteristics by temperature change of $SF_6$ gas and insulation characteristics about liquid $SF_6$ in GIS(Gas Insulated Switchgear) were described. From this result, at low temperature, the breakdown voltage was increased with a drop of temperature and an increase of the inner pressure in GIS. The ability of insulation in liquid $SF_6$ was higher than that of the highly pressurized $SF_6$ gas. A liquid $SF_6$ discharge characteristics was caused by bubble formed evaporation of liquid $SF_6$ and bubble when high voltage apply to electrode. Corona was happened to weak bubble and was proceed to new bubble breakdown.