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Volume 27(7); July 2014

Intelligent Energy Harvesting Power Management and Advanced Energy Storage System
Kwan Jun Heo, Sung Jin Kim
J Electr Electron Mater 2014;27(7):417-427.   Published online July 1, 2014
Renewable energy sources such as solar, wind and hydro provides utilizing renewable power and reduce the using fossil fuels. On the other hand, it is too critical to apply power system due to the intermittent nature of renewable energy sources, the continuous fluctuations of the power load, and the storage with high energy density. Energy storage system, including pumped-hydroelectric energy storage, compressed-air energy storage, superconducting magnetic energy storage, and electrochemical devices like batteries, super capacitors and others have shown that solve some of the challenges. In this paper, were view the current state of applications of energy storage systems, and atomic layer deposition technology, graphene materials on the energy storage systems and processes.
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Anisotropy of the Hall Factor According to the Growth Direction in the Two-dimensional Device with Indirect Conduction Valley
Jong Gu Kim, Jae Chul Lee, Sang Kook Chun
J Electr Electron Mater 2014;27(7):428-432.   Published online July 1, 2014
The Hall factor in a two-dimensional device with indirect conduction valleys is calculated for several growth on various strain conditions. In the [001] or [111] growth direction, the two-dimensional constant energy surfaces of occupied valleys are shown to be isotropic ally distributed. However, in the [110] growth direction, the distribution of occupied valleys on the plane is not isotropic. This fact is the reason for the anisotropic Hall factor on the sample plane.
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Thickness Effects of Active Layers on the Properties of Zinc Tin Oxide Transparent Thin Film Transistors
Tae Young Ma
J Electr Electron Mater 2014;27(7):433-437.   Published online July 1, 2014
Transparent thin film transistors were fabricated on n+-Si wafers coated by Al2O3/SiO2. Zinctin oxide (ZTO) films deposited by rf magnetron sputtering were employed for active layers. The mobility(μs), threshold voltage (VT), and sub threshold swing (SS) dependances on ZTO thickness were analyzed. The VT decreased with increasing ZTO thickness. The μs raised from 5.1 cm2/Vsec to 27.0 cm2/Vsec byincreasing ZTO thickness from 7 nm to 12 nm, and then decreased with ZTO thickness above 12 nm. The SS was proportional to ZTO thickness.
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Comparative Analysis of Channel Length Dependence of NBTI and CHC Characteristics in PMOSFETs
Jae Nam Yu, Sung Kyu Kwon, Jong Kwan Shin, Sun Ho Oh, Sung Yong Jang, Hyung Sub Song, Ga Won Lee, Hi Deok Lee
J Electr Electron Mater 2014;27(7):438-442.   Published online July 1, 2014
Channel length dependence of NBTI (negative bias temperature instablilty) and CHC (channel hot carrier) characteristics in PMOSFET is studied. It has been considered that HC lifetime of PMOSFET is larger than NBTI lifetime. However, it is shown that CHC degradation is greater than NBTI degradation for PMOSFET with short channel length. 1/f noise and charge pumping measurement are used for analysis of these degradations.
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Effect of Mn on the Growth of ZnO Crystals via a Thermal Evaporation of Zn-Mn Mixture
Geun Hyoung Lee
J Electr Electron Mater 2014;27(7):443-447.   Published online July 1, 2014
ZnO crystals with different morphologies were synthesized through a thermal evaporation of Zn-Mn mixtures in air. The morphology was dependant on the Mn content in Zn-Mn mixture. The morphology was changed from rod to tetrapod shape with decreasing Mn content in Zn-Mn mixture. There sult indicates that the concentration of Mn might be responsible for the different morphologies of ZnOcrystals. XRD spectra showed that the ZnO crystals had a hexagonal wurtzite crystal strutures. For all the samples, room temperature cathodoluminescence spectra showed a ultra-violet emission at 380 nm and a green emission at around 500 nm. However, the intensity ratio of ultra-violet emission to green emission was significantly different with the Mn content in the source material.
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Thin Films and Sensors : Fabrication and Characterization of AAO Template with Variation of the Phosphoric Acid Amount of the Etching Solution
Ye Won Jo, Yong Jun Kim, Jin Ho Yeo, Sung Gap Lee, Young Gon Kim
J Electr Electron Mater 2014;27(7):448-451.   Published online July 1, 2014
Anodic aluminum oxides (AAO) fabricated by the two-step anodizing process have attracted much attention for the fabrication of nano template because of pore structure with high aspect ratio, low cost process and ease of fabrication. AAOs are characterized by a homogeneous morphology of parallelpores that grow perpendicular to the template surface with a narrow distribution of diameter, length and inter-pores spacing, all of which can be easily controlled by suitably choosing of the anodizingparameters such as pH of the electrolyte, anodizing voltage and duration of anodizing. In this study, AAOtemplates were characterized by X-ray diffraction and field-emission scanning electron microscope(FE-SEM). The dependence of the pore size change according to the amount of addition of phosphoric acid, which was used to remove the initial alumina oxide layer, was not observed.
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Thin Films and Sensors : Micro-structure and NTCR Characteristics of Copper Manganite Thin Films Fabricated by MOD Process
Kui Woong Lee, Chang Jun Jeon, Young Hun Jeong, Ji Sun Yun, Joong Hee Nam, Jeong Ho Cho, Jong Hoo Paik, Jong Won Yoon
J Electr Electron Mater 2014;27(7):452-457.   Published online July 1, 2014
Copper manganite thin films were fabricated on SiNx/Si substrate by metal organic decomposition (MOD) process. They were burned-out at 400℃ and annealed at various temperatures (400∼800℃) for 1h in ambient atmosphere. Their micro-structure and negative temperature coefficient of resistance (NTCR) characteristics were analyzed for micro-bolometer application. The copper manganitefilm with a cubic spinel structure was well developed at 500℃ which confirmed by XRD and HRTEM analysis. It showed a low resistivity (47.5 Ω·cm) at room temperature and high NTCR characteristics of-4.12%/℃ and -2.15%/℃ at room temperature and 85℃, implying a good thin film for micro-bolometer application. Furthermore, its crystallinity was enhanced with increasing temperature to 600℃. However, the appearance of secondary phase at temperatures higher than 600℃ lead to deteriorate the NTCR characteristics.
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Thin Films and Sensors : Effects of RF Power on Physical and Electrical Characteristics of TiC Thin Films Deposited by Magnetron Sputtering
Nam Hoon Kim, Yong Seob Park
J Electr Electron Mater 2014;27(7):458-461.   Published online July 1, 2014
TiC thin films were deposited on Si wafer by unbalanced magnetron sputtering (UBMS) system with two targets of graphite and titanium. During the TiC sputtering, the RF power was varied from 100 W to 175 W and the physical and electrical properties of TiC films were investigated. The hardness and rms surface roughness of TiC films were improved with increasing RF power and the maximum hardness about 24 GPa and the minimum rms surface roughness about 1.2 nm were obtained. The resistivity of TiC films was decreased with increasing RF power. Consequently, the physical and electrical properties of TiC film wewe improved with increasing RF power.
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Electromagnetic Wave Absorbing Properties of FeSiCr and Fe50Ni Flaky Powder-Polymer Composite Sheet
Seok Moon Lee, Sang Mun Kim
J Electr Electron Mater 2014;27(7):462-467.   Published online July 1, 2014
In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about 1 μm and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6~4 while those values at above 500 MHz were decreased 0.4~2.5 according to the change of contents of FeSiCr and Fe50Nipowders. As a result, the reflection loss can be moved to the lower frequency from 2∼3 GHz to 1∼1.5GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.
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Nano and Oxide Electronics : Characteristics and Preparation of CNT:ZnO Gas Sensors
So Jin Yoon, Il Yu
J Electr Electron Mater 2014;27(7):468-471.   Published online July 1, 2014
The effects of ZnO coating on the sensing properties of CNT:ZnO based gas sensors were studied for H2S gas. The nano ZnO sensing materials were grown by hydrothermal reaction method. CNT:ZnO was prepared by ball-mill method. The mole range of nano ZnO coating on CNT surface was from 0 to 10%. The CNT:ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the CNT:ZnO sensing materials were investigated by XRD, EDS, SEM and TEM. The XRD patterns showed that CNT:ZnO powders with hexagonal structure were grown with (002) dominant peak. The diameter of CNT from TEM was about28 nm.
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Nano and Oxide Electronics : A Study of Thin-Film Transistor with Mg0.1Zn0.9O/ZnO Active Structure
Jong Hoon Lee, Hong Seung Kim, Nak Won Jang, Young Yun
J Electr Electron Mater 2014;27(7):472-476.   Published online July 1, 2014
We report the characteristics of thin-film transistor (TFT) to make the bi-channel structure with stacked Mg0.1ZnO0.9O (Mg= 10 at.%) and ZnO. The ZnO and Mg0.1Zn0.9O thin films were deposited by radio frequency (RF) co-sputter system onto the thermally oxidized silicon substrate. A total thickness of active layer was 50 nm. Firstly, the ZnO thin films were deposited to control the thickness from 5 nmto 30 nm. Sequentially, the Mg0.1Zn0.9O thin films were deposited to change from 45 nm to 20 nm. Thebi-layer TFT shows more improved properties than the single layer TFT. The field effect mobility and sub threshold slope for Mg0.1Zn0.9O/ZnO-TFT are 7.40 cm2V-1s-1 and 0.24 V/decade at the ZnO thickness of 10 nm, respectively.
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Energy Materials : Photoluminescence Properties of CaNb2O6:RE3+ (RE= Sm, Eu) Phosphors
Woon Hwan Joeng, Shinho Cho
J Electr Electron Mater 2014;27(7):477-482.   Published online July 1, 2014
CaNb2O6:RE3+ (RE=Sm or Eu) phosphor powders were prepared with different contents of activatorions by using solid-state reaction method. The X-ray diffraction patterns exhibited that the phosphors synthesized with different activator ions showed an orthorhombic system with a main (131) diffraction peak. The maximum size of the grain particles, determined from the measurement of scanning electron microscopy, was observed at 0.05 mol of Eu3+ ions and at 0.01 mol of Sm3+. As for the Eu3+-doped phosphor powders, the excitation spectra were composed of a broad band peaked at 278 nm and several weak bands in the range of 350~500 nm, and the highest red emission spectrum was observed at 0.15 mol of Eu3+ ions. As for the Sm3+-activated phosphor powders, three strong emission bands under excitation at 273 nm were observed at 570, 612, and 659 nm, respectively. The intensities of all the emission bands approached maxima for 0.05mol of Sm3+ ions. The optical properties show that the Eu3+- or Sm3+-doped CaNb2O6 powders are promising red-orange emitting phosphor powders applicable to full-color photonic devices.
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