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Volume 28(5); May 2015

Trends of Deep UV-LED Technology for the Pathogen and Biotoxin Aerosol Detection System
Eugene Chong, Young Su Jeong, Kibong Choi
J Electr Electron Mater 2015;28(5):277-284.   Published online May 1, 2015
The humans are under attack involving the hazardous environment and pathogen/biotoxin aerosol that is realistic concerned. A portable, fast, reliable, and cheap Pathogen and Biotoxin Aerosol threat Detection(PBAD) trigger is an important technology for detect-to-protect and detect-to-treat system because the man-made biological terror is a fast and lethal infection. The ultraviolet C(UVC) wavelengths light source is key issue for PBAD that is sensitive because of strong fluorescence cross section from fluorescent amino acids in proteins such as tryptophan and tyrosine. The UVC-light emitting diode(LED) is emerging light source technology as alternative to laser or lamps as they offer several advantages. This paper discussed about the design consideration of UVC-LED for the PBAD system. The UVC-LED and PBAD technology, currently available or in development, are also discussed.
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Effect of GaGe Sputtering Power on Ga Doping in Phase Change Memory Materials
Soon Won Jung, Seung Yun Lee
J Electr Electron Mater 2015;28(5):285-290.   Published online May 1, 2015
The phase change memory material is an active element in phase change memory and exhibits reversible phase transition behavior by thermal energy input. The doping of the phase change memory material with Ga leads to the increase of its crystallization temperature and the improvement of its amorphous stability. In this study, we investigated the effect of GaGe sputtering power on the formation of the phase change memory material including Ga. The deposition rate linearly increased to a maximum of 127 nm and the surface roughness remained uniform as the GaGe sputtering power increased in the range from 0 to 75 W. The Ga concentration in the thin film material abruptly increased at the critical sputtering power of 60 W. This influence of GaGe sputtering power was confirmed to result from a combined sputtering-evaporation process of Ga occurring due to the low melting point of Ga (29.77℃).
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Improvement of Electrical Performance and Stability in ZnO Channel TFTs with Al Doped ZnO Layer
Ki Yun Eom, Kwang Seok Jeong, Ho Jin Yun, Seung Dong Yang, Jin Seop Kim, Ga Won Lee
J Electr Electron Mater 2015;28(5):291-294.   Published online May 1, 2015
Recently, ZnO based oxide TFTs used in the flexible and transparent display devices are widely studied. To apply to OLED display switching devices, electrical performance and stability are important issues. In this study, to improve these electrical properties, we fabricated TFTs having Al doped Zinc Oxide (AZO) layer inserted between the gate insulator and ZnO layer. The AZO and ZnO layers are deposited by Atomic layer deposition (ALD) method. I-V transfer characteristics and stability of the suggested devices are investigated under the positive gate bias condition while the channel defects are also analyzed by the photoluminescence spectrum. The TFTs with AZO layer show lower threshold voltage (Vth) and superior sub-threshold slop. In the case of Vth shift after positive gate bias stress, the stability is also better than that of ZnO channel TFTs. This improvement is thought to be caused by the reduced defect density in AZO/ZnO stack devices, which can be confirmed by the photoluminescence spectrum analysis results where the defect related deep level emission of AZO is lower than that of ZnO layer.
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Electrical Properties of Vanadium-doped Lanthanium Silicates for SOFCs
Dong Jin Lee, Sung Gap Lee, Min Ho Kim, Kyeong Min Kim
J Electr Electron Mater 2015;28(5):295-299.   Published online May 1, 2015
In this paper to improve the ionic conduction properties, lanthanum silicate apatite La9.33(SiO4)6O2 ceramic, which substituted by V ions at Si-site, were fabricated by the mixed-oxide method. And we investigated the structural and electrical properties of La9.33(Si6-□v□)6O26 specimens with variation of dopants for the application of solid oxide fuel cells. The sintering temperature of La9.33(Si6-□v□)O26 specimens decreased from 1,600℃ to 1,400℃. As results of X-ray diffraction patterns, all La9.33(Si6-□-□)O26 specimens showed the formation of a complete solid solution in a apatite polycrystallin structure. But the specimens doped with more than 1.5mol% showed the second phase, La2 SiO5 and SiO2. The specimen dopants with 1.0 mol% showed the maximum ion conductivity. Ion conducting and activation energy of the La9.33(Si5V1)O26 specimens were about 7.8×10-4 S/cm 1.62 eV at 600℃, respectively.
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Thin Films and Sensors : Photocatalyst Surface Properties of the Oxide Thin Films According to the Plasma Etching Process
Chang Hyun Lee, Sung Bo Seo, Ji Yong Oh, Ik Hyeon Jin, Sun Young Sohn, Hwa Min Kim
J Electr Electron Mater 2015;28(5):300-305.   Published online May 1, 2015
WO3, SiO2, and TiO2 films with hydrophilic property are deposited by rf-magnetron sputtering. Their wettability is strongly depends on the presence or absence of the oxygen plasma etching on the glass substrates. The TiO2 film of 50 nm-thick on the plasma etched glass shows a water contact angle (WCA) below 5o which means a super-hydrophilic surface. However, WCA values are gradually degraded when the films are exposed under atmosphere, especially WO3. In order to improve hydrophilic property, the degraded films can be again recovered by UV illumination for 10 sec using UV-light and the TiO2 film shows a super-hydrophilic surface about 3o.
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Display and Optical Devices : Study on Optical Control Layer for Micro Pattern Shape Change Using Thermal Reflow Process
Min Ho Seong, Ji Min Cha, Seong Cheol Moon, Si Hong Ryung, Seong Eui Lee
J Electr Electron Mater 2015;28(5):306-313.   Published online May 1, 2015
In this study, the change of optical characteristics was studied according to the micro optical pattern provided by photo lithography followed by thermal reflow process. The shape and luminance variation with micro pattern was evaluated by SEM and spectrometers. Also, we analyzed the luminance characteristics using the 3D-optical simulation (Optis works) program. As a result, we found that the radius of curvature(R) in micro pattern is decreased up to 77%(150℃) compared to the radius of curvature at the condition 100℃, which is caused by efficient reflow of organic material without chemical changes. The highest enhancement of brightness with optimum micro pattern was obtained at the condition of 120℃ reflow process. The brightness gain with optical micro patterns is more than 15% at the condition of R=16.95 um, θ =77.14° compared to original optical source. The results of light simulation with various radius of curvature and side angle of pattern shows the similar result of experiment evaluation of light behavior on optical micro patterns. It is regarded that the more effect on light enhancement was contributed by side angle which is effective factor on light reflection, rather than the curvature of micro-patterns.
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Display and Optical Devices : Preparation and Characterization of Cy3 Dye with Various Counter Cations
Sang Dong Lee, Dong Kyoun Hyun, Yeon Tae Jeong
J Electr Electron Mater 2015;28(5):314-319.   Published online May 1, 2015
In this research, we focused on the development of cy3 dye with high thermal stability and good solubility for LCD color filter. Cy3 dyes were prepared through the synthetic procedure of two steps. The synthesized cy3 dyes were characterized by using NMR, FT-IR, UV/Vis spectroscopy, and TGA. These cy3 dyes showed maximum absorption wave length (λmax) in the range of 549∼555 nm in UV/Vis spectrum. And we confirmed that solubility characteristics and thermal stability of cy3 dyes were dependent on the structure of counter cation. Cy3 dyes with methyl counter cation and ethyl counter cation have good solubility in organic solvents such as chloroform, ethanol, and PGME. Moreover, Cy3 dye with ethyl counter cation gave excellent thermal stability in TGA thermograms. And Cy3 dye with ethyl counter cation showed good result in photoresist film test.
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High Voltage and Discharge Engineering : Identification of Defect Type by Analysis of a Single PD Pulse in Gas Insulated Structure
Hyang Eun Jo, Sun Jae Kim, Gi Woo Jeong, Gyung Suk Kil
J Electr Electron Mater 2015;28(5):320-325.   Published online May 1, 2015
This paper dealt with a defect identification algorithm which is based on single partial discharge (PD) pulse analysis in gas insulated structure. Four types of electrode systems such as a needle-plane, a plane-needle, a free particle and a crack inside spacer were fabricated to simulate defects in gas insulated switchgear (GIS). We measured single PD pulse by an oscilloscope with a sampling rate of 5 GS/s and a frequency bandwidth of 1 GHz. Data aquisition and signal processing were controlled by a LabVIEW program. Physical shapes of PD pulses were compared with kurtosis, skewness and time-based parameters as rising time, falling time and pulse-width. These parameters were analysed by an algorithm with a back propagation algorithm (BPA). By applying the algorithm, the identification rate was 97% for the needle-plane electrode, 96% for the plane-needle electrode, 91% for the free particle and 93% for the crack inside spacer. The results verified that the algorithm could identify the type of defects in GIS.
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High Voltage and Discharge Engineering : Shape and Dielectric Strength of Thermal Bubbles in Liquid Nitrogen
Seung Myeong Baek, Hae Jong Kim
J Electr Electron Mater 2015;28(5):326-331.   Published online May 1, 2015
In this paper, we study the insulating properties of the liquid nitrogen(LN2) including the thermal bubbles. The shape of the thermal bubbles in accordance with the current change was observed in the 77 K and 65 K LN2. According to the temperature of liquid nitrogen, bubbles were generated differently. The round shape of the bubble is occurred in 77 K LN2. But the layer shape of bubble is occurred in 65 K LN2. When the bubbles present, the dielectric strength of liquid nitrogen is low. However, the breakdown patterns were different according to the electrode arrangement. AC breakdown voltage(BDV) was lower than the DC BDV due to the influence of bubbles. Therefore, the design of a high-voltage superconducting equipments should consider the bubbles.
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Energy Materials : Effects of Ag on the Characteristics of Sn-Pb-Ag Solder for Photovoltaic Ribbon
Yeon Su Son, Tae Sik Cho
J Electr Electron Mater 2015;28(5):332-337.   Published online May 1, 2015
We have studied the effects of Ag on the characteristics of Sn60Pb40Agx (wt%) solder for photovoltaic ribbon. Ag atoms in the solder formed an alloy phase of Ag3Sn after reacting with some part of Sn atoms, while they did not react with Pb atoms, but decreased the mean size of Pb solid phase. The enhancement of peel strength between solar cell and ribbon is an important part in the developments of long-lifespan solar module. The peel strength of the solder ribbon of Sn60Pb40 (wt%) was 169 N/mm2, and it was largely enhanced by adding a small amount of Ag atoms. The maximum peel strength was 295 N/mm2 in the solder ribbon of Sn60Pb40Ag2 (wt%). This result is caused by the high binding energy of 162.9 kJ/mol between Ag atoms in the solder and Ag atoms in Ag sheet.
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Energy Materials : Feasibility Test of One-Dimensional Sodium Hexatitanate as an Anode Material in Dye-Sensitized Solar Cells
Badema, Kwang Joong, Kuk Cho
J Electr Electron Mater 2015;28(5):338-343.   Published online May 1, 2015
Dye sensitized solar cells (DSSCs), which is one of the contending renewable energy sources, have the problem of low efficiency. To improve the efficiency, the fast electron transport and long electron lifetime are required. In this study, one-dimensional sodium hexatitanate, which is expected to have an advantageous structure for electron transports, was synthesized and the feasibility of the material on DSSC was tested. Its physical properties were characterized by the SEM, XRD, and BET method. The dye adsorption and solar cell properties were also characterized. In addition to the expectation of fast electron transport, sodium hexatitanate showed longer electron lifetime: This means sodium hexatitanate can improve the DSSC efficiency. However, it showed low current and voltage because of the low surface area leading to the low amount of dye adsorbed. Therefore, it should be mixed with titanium oxide with high surface area for the optimal performance.
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Light Source and Application Technology : An Efficiency Improvement of the OLEDs due to the Thickness Variation on Hole-Iniection Materials
Jong Yeol Shin, Yi Wei Guo, Tae Wan Kim, Jin Woong Hong
J Electr Electron Mater 2015;28(5):344-349.   Published online May 1, 2015
A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/Alq3/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/Alq3/BCP/Lif/Al were studied experimentally.
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