• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.1001-1007
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• 2001

In this study, high dielectric materials, (Pb,La)Ti $O_3$ thin films were fabricated by PLD (Pulsed Laser Deposition) method and investigated in terms of structural and electrical characteristics in order to develope the dielectric materials for the use of new capacitor layers of Giga bit-level DRAM. The deposition conditions were examined in order to fabricate uniform thin films through systematic changes of oxygen pressures and substrate temperature. The uniform thickness and smooth morphology of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were obtained at the conditions of substrate-target distance 5.5[cm], laser energy density 2.1[J/$\textrm{cm}^2$], oxygen pressure 200[mTorr] and substrate temperature 500[$^{\circ}C$]. After the (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were fabricated under the above conditions, they were post-annealed by RTA process in order to increase the dielectric constant. The film thickness of 1200 [$\AA$] had dielectric constant 821. Assuming that operating voltage is 2V, leakage current density of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films would result into 10$^{-7}$ [A/$\textrm{cm}^2$] and satisfied the specification of 256M DRAM planar capacitor, 4$\times$10$^{-7}$ [A/$\textrm{cm}^2$]m}^2$]

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.357-362
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• 2017

Among the lithium metal oxides for asymmetric hybrid supercapacitor, $Li_4Ti_5O_{12}(LTO)$ is an emerging electrode material as zero-stain material in volume change during the with the charging and discharging processes. The pulverized LTO powder was observed to show the enhanced capacity from 120 mAh/g to 156 mAh/g at C-rate (10, 100 C). Hybrid supercapacitor module(48V, 416F) was fabricated using an asymmetric hybrid capacitor with a capacitance of 7500F. As a result of the measurement of C-rate characteristics, the module shows that the discharge time is drastically reduced at more than 50C, and the ESR and voltage drop characteristics are increased. The energy density and power density were reduced under high C-rate conditions. When designing asymmetric hybrid supercapacitor module, the C-rate and ESR should be considered As a result of measuring the 5 kw UPS, it was discharged at the current of 116A~170A during the discharge in the voltage range of 48V~30V, and the compensation time at discharge was measured to be about 33.2s. Experimental results show that it can be applied to applications related to stabilization of power quality by applying hybrid supercapacitor module.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.353-360
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• 2016

Series hybrid electric vehicles (SHEVs) having multiple power sources such as an engine- generator (EnGen), a battery, and an ultra-capacitor require a power control unit with high power density and reliable control operation. However, manufacturing using separate individual power converters has the disadvantage of low power density and requires a large number of power and signal cable wires. It is also difficult to implement the optimal power distribution and fault management algorithm because of the communication delay between the units. In order to address these concerns, this approach presents a design methodology and a power control algorithm of an integrated power converter for the SHEVs powered by multiple power sources. In this work, the design methodology of the integrated power control unit (IPCU) is firstly elaborately described, and then efficient and reliable power distribution algorithms are proposed. The design works are verified with product-level and vehicle-level performance experiments on a 10-ton SHEV.

• Proceedings of the Safety Management and Science Conference
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• 2003.11a
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• pp.335-343
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• 2003

In the electrode fabrication of unit cell, it was ascertained that electrochemical characteristics were greatly increased with 90 wt.% of BP-20, 5 wt.% of Super P and 5 wt.% of mixed binder [P(VdF-co-HFP) : PVP =7 : 3] The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of Electric Double Layer Capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. The electrochemical characteristics of 2.3 V/3,000 F grade EDLC were as follows: 0.35 m of DC-ESR (100 A discharge), 0.14 mof AC-ESR (AC amplitude 100 mV), 2.80 Wh/kg (3.73 Wh/L) of energy density and 4.64 kW /kg (6.19 kW/L) of power density. Power output was compatible with electric vehicle applications, uninterrupted power supply and engine starter, in due consideration of Ragone relations.

• Clean Technology
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• v.27 no.4
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• pp.277-290
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• 2021

A supercapacitor, also called an ultracapacitor or an electrochemical capacitor, stores electrochemical energy by the adsorption/desorption of electrolytic ions or a fast and reversible redox reaction at the electrode surface, which is distinct from the chemical reaction of a battery. A supercapacitor features high specific power, high capacitance, almost infinite cyclability (~ 100,000 cycle), short charging time, good stability, low maintenance cost, and fast frequency response. Supercapacitors have been used in electronic devices to meet the requirements of rapid charging/discharging, such as for memory back-up, and uninterruptible power supply (UPS). Also, their use is being extended to transportation and large industry applications that require high power/energy density, such as for electric vehicles and power quality systems of smart grids. In power generation using intermittent power sources such as solar and wind, a supercapacitor is configured in the energy storage system together with a battery to compensate for the relatively slow charging/discharging time of the battery, to contribute to extending the lifecycle of the battery, and to improve the system power quality. This article provides a concise overview of the principles, mechanisms, and classification of energy storage of supercapacitors in accordance with the electrode materials. Also, it provides a review of the status of recent research and patent, product, and market trends in supercapacitor technology. There are many challenges to be solved to meet industrial demands such as for high voltage module technologies, high efficiency charging, safety, performance improvement, and competitive prices.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1082-1089
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• 2017

Negative output elementary super lift Luo converter (NOESLLC), which has the significant advantages including high-voltage transfer gain, high efficiency, high power density, and reduced output voltage/inductor current ripples when compared to the traditional DC-DC converters, is an attractive DC-DC converter for the field of negative DC voltage applications. In this study, in consideration of the voltage across the energy transferring capacitor changing abruptly at the beginning of each switching cycle, the improved averaged model of the NOESLLC operating in continuous conduction mode (CCM) is established. The improved DC model and transfer functions of the system are derived and analyzed. The current mode control is applied for this NOESLLC. The results from the theoretical calculations, the PSIM simulations and the circuit experiments show that the improved DC model and transfer functions here are more effective than the existed ones of the NOESLLC to describe its real dynamical behaviors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1226-1229
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• 2004

Supercapacitors, also known as electrochemical capacitors, are being extensively studied due to an increasing demand for energy-storage systems. These devices offer many advantages over conventional secondary batteries, which include the ability of fast charge propagation, long cycle-life and better storage efficiency. That is to say supercapacitor bridges the gap between conventional capacitors and batteries. A new type electric double layer capacitor (EDLC) also called supercapacitors. Recently, supercapacitors concerns about their high power density and energy density. So we experiment with EDLC by using carbon nanofibers (CNFs) and DAAQ(1,5-diaminoanthraquinone) electrode. The electrode for supercapacitor was prepared by synthesis of DAAQ covered CNFs. CNFs could be covered with very thin DAAQ oligomer from the results of CV, XRD, DSC, SEM images, and TEM images. Dissolved electrode active material in NMP solution has been drop-coated on carbon plate. Its electrochemical characteristics were investigated by cyclic voltammograms. And compared with different electrolyte of aqueous type. As a result, CNFs coated by DAAQ composite electrode showed relatively good electrochemical behaviors with respect to specific capacity and scan rate dependency.

• Journal of Multimedia Information System
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• v.5 no.1
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• pp.47-52
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• 2018

We have developed an electromagnetic generator to bury in subcutaneous area or abdominal cavity of the birds. As we can't use a solar battery, it is extremely difficult to supply a power for subcutaneous implantation such as biosensors under the skin due to the darkness environment. We are aiming to test the antigen-antibody reaction to confirm an avian influenza. One solution is a very small generator with the electromagnetic induction coil. We attached the developed coil to chickens and pheasants and recorded the electric potential generated as the chicken walked and the pheasant flew. The electric potential generated with physical simulator is equal to or exceeds the 7 V peak-to-peak at maximum by 560/min of flapping of wings. Even if we account for the junction voltage of the diode (200 mV), efficient charging of the double-layer capacitor is possible with the voltage doubler rectifier. If we increase the voltage, other problems arise, including the high-voltage insulation of the double-layer capacitor. For this reason, we believe the power generated to be sufficient for subcutaneous area of birds. The efficiency, magnetic 2 mm in length and coil 15mm in length, if axial direction is rectified, the magnetic flux density given to the coil could calculated to 7.1 % and generated power average 0.47mW. The improvements in size and wire insulation are expected in the future.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.176.2-176.2
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• 2013

Property of optical diagnostics for pulse-discharged plasma in liquid and its biological applications to proteins are investigated by making use of high voltage Marx generator. The Marx generator has been consisted of 5 stages, where each charging capacitor is 0.5 ${\mu}F$, to generate a high voltage pulse with rising time of $1{\mu}s$. We have applied an input voltage of 6 kV to the each capacitor of 0.5 ${\mu}F$. High voltage pulsed plasma has been generated inside a polycarbonate tube by a single-shot operation, where the breakdown voltage is measured to be 7 kV, current of 1.2 kA, and pulse width of ~ 1 ${\mu}s$ between the two electrodes of anode-cathode whose material is made of tungsten pin, which are immersed into the liquids. We have investigated the emitted hydrogen lines for optical diagnostics of high voltage pulsed plasma. The emission line of 656.3 nm from $H-{\alpha}$ and 486.1 nm from $H-{\beta}$ have been measured by a monochromator. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium conditions, the electron temperature and density of the high voltage pulsed plasma in liquid could be obtained by the Stark broadening of optical emission spectroscopy. For the investigation of the influence of pulsed plasma on biological proteins, we have exposed it onto the proteins such as hemoglobin and myoglobin. The structural changes in these proteins and their analysis have also been obtained by circular dichroism (CD) and ultraviolet (UV) visible spectroscopy.

• Korean Journal of Materials Research
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• v.34 no.6
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• pp.283-290
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• 2024

The aggressive scaling of dynamic random-access memory capacitors has increased the need to maintain high capacitance despite the limited physical thickness of electrodes and dielectrics. This makes it essential to use high-k dielectric materials. TiO₂ has a large dielectric constant, ranging from 30~75 in the anatase phase to 90~170 in rutile phase. However, it has significant leakage current due to low energy barriers for electron conduction, which is a critical drawback. Suppressing the leakage current while scaling to achieve an equivalent oxide thickness (EOT) below 0.5 nm is necessary to control the influence of interlayers on capacitor performance. For this, Pt and Ru, with their high work function, can be used instead of a conventional TiN substrate to increase the Schottky barrier height. Additionally, forming rutile-TiO₂ on RuO₂ with excellent lattice compatibility by epitaxial growth can minimize leakage current. Furthermore, plasma-enhanced atomic layer deposition (PEALD) can be used to deposit a uniform thin film with high density and low defects at low temperatures, to reduce the impact of interfacial reactions on electrical properties at high temperatures. In this study, TiO₂ was deposited using PEALD, using substrates of Pt and Ru treated with rapid thermal annealing at 500 and 600 ℃, to compare structural, chemical, and electrical characteristics with reference to a TiN substrate. As a result, leakage current was suppressed to around 10^-6 A/cm² at 1 V, and an EOT at the 0.5 nm level was achieved.