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Volume 28(3); March 2015

The Relationship Between the Lag Time of the Discharge and the Characteristics of Mis-Discharge in an AC-PDP
Jae Hwa Shin, Gun Su Kim
J Electr Electron Mater 2015;28(3):149-153.   Published online March 1, 2015
As the temperature of the panel increases in AC-PDPs, the minimum driving voltage increases. Also, as the more the number of discharge increases in cells, the probability of the strong dark discharge in the reset period increases. In this study, we investigated the relationship between the lag time of the discharge and the mechanism of mis-discharges which are the black noise and bright noise. We conclude that the variation of time lag characterizes the properties of exo-electron emission from MgO. Thus, we found that the main factor of the mis-discharges is the rate of change of the electron emission ability from the MgO surface.
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Simulation Method of Temperature Dependent Threshold Voltage Shift in Metal Oxide Thin-film Transistors
Se Yong Kwon, Tae Ho Jung
J Electr Electron Mater 2015;28(3):154-159.   Published online March 1, 2015
In this paper, we propose a numerical method to model temperature dependent threshold voltage shift observed in metal oxide thin-film transistors (TFTs). The proposed model is then implemented in AIM-SPICE circuit simulation tool. The proposed method consists of modeling the well-known stretched-exponential time dependent threshold voltage shift and their temperature dependent coefficients. The outputs from AIM-SPICE tool and the stretched-exponential model at different temperatures in the literature are compared and they show a good agreement. Since metal oxide TFTs are the promising candidate for flat panel displays, the proposed method will be a good stepping stone to help enhance reliability of fast-evolving display circuits.
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Dielectric and Piezoelectric Properties of Low Temperature Sintering PMW-PNN-PZT Substituted with CeMnO3
Yong Jin Kim, Ju Hyun Yoo
J Electr Electron Mater 2015;28(3):160-164.   Published online March 1, 2015
In this study, (1-x)Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3 + xCeMnO3 (x= 0∼0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [g/cm3] were obtained when the substitution amount of CeMnO3 is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor(Qm) of 1,091 and the electromechanical coupling factor(kp) of 0.613.
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Dielectric and Piezoelectric Properties of PMW-PNN-PZT Ceramics As a Function of ZnO Addition
Cheol Min Ra, Ju Hyun Yoo
J Electr Electron Mater 2015;28(3):165-169.   Published online March 1, 2015
In this paper, in order to develop the composition ceramics with the excellent dielectric properties, Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3 ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties (d33= 422pC/N, d31= 161 pC/N, εr= 1,905, kp= 0.55, Qm= 160) were obtained.
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Fabrication and Characterization of Alumina-TZP(3Y) Composite Ceramics
Jae Jung Yoon, Myung Pyo Chun, San Nahm
J Electr Electron Mater 2015;28(3):170-174.   Published online March 1, 2015
Composite ceramics of alumina-TZP(3Y) have good mechanical and electrical properties. So, They have been used as high strength refractory materials and thick film substrates, etc. In this study, Composite ceramics of alumina-TZP(3Y) were fabricated by uniaxial pressing and sintering at 1,400, 1,500, and 1,600℃, and their microstructures and mechanical properties were investigated. As the TZP(3Y) content in composite ceramics increases from 20 wt.% to 80 wt.%, the fracture toughness increases monotonically, which seems to be related to the higher relative density and/or toughening mechanism by means of stabilized tetragonal zirconia phase at room temperature. In contrast to the fracture toughness, Vickers hardness of the composite ceramics shows maximum value (1,938 Hv) at a 40 wt.% of TZP(3Y). The result of Vickers hardness is likely to be due to more dense sintered microstructure of composite ceramics than pure alumina and reinforcement of composite ceramics with TZP(3Y), considering that Vickers hardness of pure Al2O3 is greater than that of TZP(3Y). It is also shown that the ZrO2 particles are 1°Cated between Al2O3 grains and suppress grain growth each other.
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Thin Films and Sensors : Regular Paper ; A Formation of Hole Pattern on Ti Electrode by Lift-off and Its Application to TCO-less Dye-sensitized Solar Cells
Haeng Yun Jung, Hyun Chul Ki, Hal Bon Gu
J Electr Electron Mater 2015;28(3):175-179.   Published online March 1, 2015
In this study, we propose Ti hole pattern structure on the transparent conductive oxide (TCO) lessdye-sensitized solar cells (DSSCs) using the lift-off process to improve the low light transmittance and lowefficiency caused by opaque Ti electrode. The formation of Ti hole patterns make it possible to move the dyeadsorption and electrolyte. The DSSCs with Ti hole patterns showed a higher photoelectric conversion efficiency(PCE) than those with general structure by 11.1%. As a result, The Ti hole pattern structure can be improved toincrease the light absorption of the dyes and PCE of the TCO-less DSSCs is also increased.
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Thin Films and Sensors : Regular Paper ; Enhanced Electrochemical Properties of Dye-sensitized Solar Cells Using Flexible Stainless Steel Mesh Electrodes with Ti Protective Layer
Haeng Yun Jung, Hyun Chul Ki, Hal Bon Gu
J Electr Electron Mater 2015;28(3):180-184.   Published online March 1, 2015
Stainless steel (SS) mesh was used to fabricate photo electrode for flexible dye-seisitzed solar cells(DSSCs) in order to evaluate them as replacements for more expensive transparent conductive oxide(TCO). We fabricated the DSSCs with new type of photo electrode, which consisted of flexible SS mesh coated with 100 nm thickness titanium (Ti) protective layer deposited using electron-beam deposition system. SS mesh DSSCs with protective layer showed higher efficiency than those without a protective layer. The best cell property in the present study showed the open circuit voltage (Voc) of 0.608 V, short-circuit current density (Jsc) of 5.73 mA cm-2, fill factor (FF) of 65.13%, and efficiency (η) of 2.44%. Compared with SS mesh based on DSSCs (1.66%), solar conversion of SS mesh based on DSSCs with protective layer improved about 47%.
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Thin Films and Sensors : Regular Paper ; Change in the Energy Band Gap and Transmittance IGZO, ZnO, AZO OMO Structure According to Ag Thickness
Seung Min Lee, Hong Bae Kim, Sang Yeol Lee
J Electr Electron Mater 2015;28(3):185-190.   Published online March 1, 2015
In this study, we fabricated the indium gallium zinc oxide (IGZO), zinc oxide (ZnO), aluminum zincoxide (AZO). oxide and silver are deposited by magnetron sputtering and thermal evaporator, respectively transparency and energy band gap were changed by the thickness of silver layer. To fabricate metal oxide metal(OMO) structure, IGZO sputtered on a corning 1,737 glass substrate was used as bottom oxide material and then silver was evaporated on the IGZO layer, finally IGZO was sputtered on the silver layer we get the final OMO structure. The radio-frequency power of the target was fixed at 30 W. The chamber pressure was set to 6.0×10-3Torr, and the gas ratio of Ar was fixed at 25 sccm. The silver thickness are varied from 3 to 15 nm. The OMO thin films was analyzed using XRD. XRD shows broad peak which clearly indicates amorphous phase. ZnO, AZO,OMO show the peak [002] direction at 34°. This indicate that ZnO, AZO OMO structure show the crystalline peak. Average transmittance of visible region was over 75%, while that of infrared region was under 20%. Energy band gap of OMO layer was increased with increasing thickness of Ag layer. As a result total transmittance was decreased.
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Evaluation on the Properties of the Current Limiting Part for Fault-Current-Limiting Type HTS Cables
Tae Min Kim, Gong Hyun Hong, Byung Sung Han, Ho Ik Du
J Electr Electron Mater 2015;28(3):191-195.   Published online March 1, 2015
Inside the existing superconducting cables, the superconducting wire carries a loss-free current, and the cable former (the stranded copper wire) bypasses the fault current to prevent damage and loss of the superconducting cable when the fault current is applied. The fault-current-limiting-type superconducting cable proposed in this paper usually carries a steady current; but in a fault state, the cable generates self-resistance that makes the fault current lower than a certain width. That is, the superconducting cable that transmitted only a low voltage and a large capacity power repetitively limits the fault current, as does a superconducting current limiter. To complete this structure, it is essential to investigate the mutual resistance relationship between the superconducting wires after applying a fault current. Therefore, in this paper, one kinds of superconducting wires (a wire without a stabilization layer) were connected parallel 4 tapes, respectively; and after applying a fault current, the current, voltage, resistance and thermal stability of the HTS thin-film wires were examined.
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Nano and Oxide Electronics : Regular Paper ; Flexible Antenna Radiator Fabricated Using the CNT/PVDF Composite Film
Yong Jin Kim, Young Taek Lim, Sun Woo Lee
J Electr Electron Mater 2015;28(3):196-200.   Published online March 1, 2015
In this paper, we fabricated flexible antenna radiator using the CNT/PVDF (carbon nanotube /polyviny lidene fluoride) composite film. We used polymer film as a matrix material for the flexible devices, and introduced CNTs for adding conductivity into the film resulting in obtaining performances of the antenna radiator. Spray coating method was used to form the CNT/PVDF composite radiator, and pattern formation of the radiator was done by shadow mask during the spray coating process. We investigated the electrical properties of the CNT/PVDF composite films with the CNT concentration, and also estimated the radiator performance. Finally we discuss the feasibility of the CNT/PVDF composite radiator for the flexible antenna.
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Technology Education : Regular Paper ; The Insulation Design of Enclosure for Diagnostic Device in Extra High Voltage Line
Ki Joon Kim
J Electr Electron Mater 2015;28(3):201-207.   Published online March 1, 2015
In this paper, in order to avoid equipment malfunction due to electromagnetic waves, which can occur when high-voltage live line diagnostic device fabrication, the enclosure structure of the diagnostic device with power lines that can minimize the EMI (electromagnetic interference) was modeled using the FEM (finite element method). Simulation examined the strength of the electric field in the required thickness, material and regions where there is a control board while changing the curvature radius of the corner making the enclosure, and By applying a mechanical design and simulation results that occur during the actual production has been designed for the final design. Most of the simulation results for the electric field is concentrated in the final model, the inner edge of the enclosure could be confirmed that the stable structure.
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Light Source and Application Technology : Regular Paper ; Thermal Design of 21 W LED Light Engine Using Thermal Conductive Plastic
Won Ho Choi, Doo Ho Choi, Jin Yeol Lee, Dae Hee Park
J Electr Electron Mater 2015;28(3):208-212.   Published online March 1, 2015
This study will design the structural optimization of 21 W LED heat sink using the thermal conductive plastic materials. The thermal conductive plastic heat sink is inferior to aluminum heat sinks in thermal properties. This study will solve this problem using formability of thermal conductive plastic heat sink. A heat sink was optimized in terms of the number, and the thickness of fins and the base thickness of the heat sink, using the Heatsinkdesigner software. Also by using Solid Works Flow simulation and thermal analysis software, the thermal characteristics of the heat sink were analyzed. As the result, the optimized heat sink has 17 fins, which are 1.5mm thick and a 3.7 mm-thick base. The highest and the lowest temperature were 51.65℃ and 46.24℃ respectively. Based on these results, The thermal conductive plastic heat sink is considered possible to overcome heating problem when designing in complex structure.
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