• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.52-57
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• 2014

The MCMB-$Li_4Ti_5O_{12}$ with core-shell structure was prepared by sol-gel process to improve low cycle capability of MCMB in this study. The electrochemical characteristics were investigated for hybrid capacitor using MCMB-$Li_4Ti_5O_{12}$ as the negative electrode and $LiMn_2O_4$, Active carbon fiber as the positive electrode. The electrochemical behaviors of hybrid capacitor using organic electrolytes ($LiPF_6$, EC/DMC/EMC) were characterized by charge/discharge, cyclic voltammetry, cycle and impedance tests. The hybrid capacitor using MCMB-$Li_4Ti_5O_{12}/LiMn_2O_4$ electrodes had better capacitance than MCMB hybrid systems and was able to deliver a specific energy with 67 Wh/kg at a specific power of 781 W/kg.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.6
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• pp.427-434
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• 2013

In this paper, the design and layout of a 2.5 Gbps arrayed VCSEL driver for optical transceiver having arrayed multi-channel of integrating module is confirmed. In this paper, a 4 channel 2.5 Gbps VCSEL (vertical cavity surface emitting laser) driver array with automatic optical power control is implemented using $0.18{\mu}m$ CMOS process technology that drives a $1550{\mu}m$ high speed VCSEL used in optical transceiver. To enhance the bandwidth of the optical transmitter, active feedback amplifier with negative capacitance compensation is exploited. We report a distinct improvement in bandwidth, voltage gain and operation stability at 2.5Gbps data rate in comparison with existing topology. The 4-CH chip consumes only 140 mW of DC power at a single 1.8V supply under the maximum modulation and bias currents, and occupies the die area of $850{\mu}m{\times}1,690{\mu}m$ excluding bonding pads.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.510-515
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• 1994

Yttria-stabilized zirconia(YSZ) films were prepared onto p-type (100) silicon wafer by a plasma-enhanced metallorganic chemical vapor deposition(PE MO CVD) processing involving the application of vapor mixture of tri(2.2.6.6-tetramethyl-3, 5-heptanate) yttrium$[Y(DPM)_3]$, zirconiumtriflouracethyla cetonate$(Zr(tfacac)_4$ and oxygen gas. The x-ray diffraction(XRD) and fourier transform infrared spectra(FT1R) results showed that the deposited YSZ films had a single cubic phase. $Y_2O_3$ content of YSZ film was analyzed by PIXE(partic1e induced x-ray emission). The experimental results by PIXE revealed that 12.lmol%, 20.4mol% and 31.6mol% $Y_2O_3$ could be obtained as the $Y(DPM)_3$ bubbling temperature varied at $160^{\circ}C, 165^{\circ}C$ and $170^{\circ}C$ respectively. The increase of $Y(DPM)_3$ bubbling temperature caused shifting flat band voltage to have a negative value.

• Electronic Materials Letters
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• v.14 no.6
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• pp.669-677
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• 2018

In this work, the high ${\kappa}$ $Zr_xAl_{1-x}O_y$ films with a different Zr concentration have been deposited by atomic layer deposition, and the effect of Zr concentrations on the structure, chemical composition, surface morphology and dielectric properties of $Zr_xAl_{1-x}O_y$ films is analyzed by Atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and capacitance-frequency measurement. The effect of Zr concentrations of $Zr_xAl_{1-x}O_y$ gate insulator on the electrical property and stability under negative bias illumination stress (NBIS) or temperature stress (TS) of ZnSnO (ZTO) TFTs is firstly investigated. Under NBIS and TS, the much better stability of ZTO TFTs with $Zr_xAl_{1-x}O_y$ film as a gate insulator is due to the suppression of oxygen vacancy in ZTO channel layer and the decreased trap states originating from the Zr atom permeation at the $ZTO/Zr_xAl_{1-x}O_y$ interface. It provides a new strategy to fabricate the low consumption and high stability ZTO TFTs for application.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.263-272
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• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.308-312
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• 2013

Active carbons with high specific surface area and micro pore structure were prepared from the coconut shell char using the chemical activation method of NaOH. The preparation process has been optimized through the analysis of experimental variables such as activating chemical agents to char ratio and the flow rate of gas during carbonization. The active carbons with the surface area (2,481 $m^2/g$) and mean pore size (2.32 nm) were obtained by chemical activation with NaOH. The electrochemical performances of hybrid capacitor were investigated using $LiMn_2O_4$, $LiCoO_2$ as the positive electrode and prepared active carbon as the negative electrode. The electrochemical behaviors of hybrid capacitor using organic electrolytes ($LiPF_6$, $TEABF_4$) were characterized by constant current charge/discharge, cyclic voltammetry, cycle and leakage tests. The hybrid capacitor using $LiMn_2O_4$/AC electrodes had better capacitance than other hybrid systems and was able to deliver a specific energy as high as 131 Wh/kg at a specific power of 1,448 W/kg.