• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.360-369
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• 2012

The causes of showing different subthreshold slopes (SS) in programmed and erased states for two different charge trap flash (CTF) memory devices, SONOS type flash memory with gate-all-around (GAA) structure and TANOS type NAND flash memory with planar structure were investigated. To analyze the difference in SSs, TCAD simulation and low-frequency noise (LFN) measurement were fulfilled. The device simulation was performed to compare SSs considering the gate electric field effect to the channel and to check the localized trapped charge distribution effect in nitride layer while the comparison of noise power spectrum was carried out to inspect the generation of interface traps ($N_{IT}$). When each cell in the measured two memory devices is erased, the normalized LFN power is increased by one order of magnitude, which is attributed to the generation of $N_{IT}$ originated by the movement of hydrogen species ($h^*$) from the interface. As a result, the SS is degraded for the GAA SONOS memory device when erased where the $N_{IT}$ generation is a prominent factor. However, the TANOS memory cell is relatively immune to the SS degradation effect induced by the generated $N_{IT}$.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.81-89
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• 2018

In this study, the effect of Nb alloying element on the corrosion fatigue properties of high strength steel is investigated by conducting fatigue experiments under corrosive condition and hydrogen induced condition, potentiodynamic polarization test, tensile test and surface analyses. Nb element is added to enhance the mechanical property of medium carbon steel. This element forms MX-type phases such as carbides and nitrides which are playing an important role in the grain refinement. The grain refinement is one of the effective way to improve mechanical property because both tensile strength and toughness can be improved at the same time. However, MX-type phase precipitates can be a susceptible site to localized corrosion in corrosive environment due to the potential difference between matrix and precipitate. The obtained results showed that Nb-added steel improved corrosion fatigue property by grain refinement. However, it is degraded for hydrogen-induced fatigue property due to Nb, Ti-inclusions acting as a stronger trap.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.57-60
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• 2008

KEPRI has studied planar type SOFC stacks using anode-supported single cells and kW class co-generation systems for residential power generation. A 1kW class SOFC system consisted of a hot box part, a cold BOP part and a water reservoir. A hot box part contains a SOFC stack made up of 48 single cells and ferritic stainless steel interconnectors, a fuel reformer, a catalytic combustor and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation. A cold BOP part was composed of blowers, pumps, a water trap and system control units. When a 1kW class SOFC system was operated at $750^{\circ}C$ with hydrogen after pre-treatment process, the stack power was 1.2kW at 30 A and 1.6kW at 50A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about 1.3kW with hydrogen and 1.2kW with city gas respectively. The system also recuperated heat of about 1.1kW by making hot water.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.142-148
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• 2009

The direct injection(DI) diesel engine has become a prime candidate for future transportation needs because of its high thermal efficiency. However, nitrogen oxides(NOx) increase in the local high temperature regions and particulate matter (PM) increases in the diffusion flame region within diesel combustion. Therefore, the demand for developing a suitable after treatment device has been increased. NOx absorbing catalysts are based on the concept of NOx storage and release making it possible to reduce NOx emission in net oxidizing gas conditions. This De-NOx system, called the LNT(Lean NOx Trap) catalyst, absorbs NOx in lean exhaust gas conditions and release it in rich conditions. This technology can give high NOx conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter at the right time. In this research, a performance characteristics of LNT with a hydrogen enriched gas as a reductant was examined and strategies of controlling the injection and rich exhaust gas condition were studied. The NOx reduction efficiency is closely connected to the injection timing and duration of reductant. LNT can reduce NOx efficiently with only 1 % fuel penalty.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.384-389
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• 2009

KEPRI (Korea Electric Power Research Institute) has studied planar type solid oxide fuel cell (SOFC) stacks using anode-supported cells and kW class co-generation systems for residential power generation. In this work, a 1 kW SOFC system consisted of a hot box part, a cold BOP (balance of plant) part, and a hot water reservoir. The hot box part contained a SOFC stack made up of 48 cells, a fuel reformer, a catalytic combustor, and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation in that system. A cold BOP part was composed of blowers, pumps, a water trap, and system control units. When the 1 kW SOFC stack was tested using hydrogen at $750^{\circ}C$, the stack power was about $1.2\;kW_e$ at 30 A and $1.6\;kW_e$ at 50 A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about $1.3\;kW_e$ with hydrogen and $1.2\;kW_e$ with city gas respectively. The system also recuperated heat of about $1.1\;kW_{th}$ by making hot water.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.257-262
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• 2011

A low capacity generator converted to high capacity of 40m3 is designed and developed in order to use the hydroxy gas in the steel manufacturing process. For efficient design, it is increased from 8 electrode tubes to 10 electrode tubes as well as expanding the diameter of cell integument up to two times bigger, which can increase the amount of hydrogen occurrence per a cell significantly. In addition, circulating pump and pipe, heat exchanger of affiliated SUS material have been used in the circulation of electrolysis catalyst, and circulating cooling section and piping design are also developed. The flame trap is designed into all-in-one suitable check valve in the flow rate of 28-35m3/h and its application is possibly applied in work operation. It is found that the efficiency of generator developed is enhanced substantially up to 84%. It is expected that the application in this field can be expanded significantly by this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.239-242
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• 1998

Ca $F_2$ films have superior gate insulator properties than conventional gate insulator such as $SiO_2$, Si $N_{x}$, $SiO_{x}$, and T $a_2$ $O_{5}$ to the side of lattice mismatch between Si substrate and interface trap charge density( $D_{it}$). Therefore, this material is enable to apply Thin Film Transistor(TFT) gate insulator. Most of gate oxide film have exhibited problems on high trap charge density, interface state in corporation with O-H bond created by mobile hydrogen and oxygen atom. This paper performed Ca $F_2$ property evaluation as MIM, MIS device fabrication. Ca $F_2$ films were deposited at the various substrate temperature using a thermal evaporation. Ca $F_2$ films was grown as polycrystalline film and showed grain size variation as a function of substrate temperature and RTA post-annealing treatment. C-V, I-V results exhibit almost low $D_{it}$(1.8$\times$10$^{11}$ $cm^{-1}$ /le $V^{-1}$ ) and higher $E_{br}$ (>0.87MV/cm) than reported that formerly. Structural analysis indicate that low $D_{it}$ and high $E_{br}$ were caused by low lattice mismatch(6%) and crystal growth direction. Ca $F_2$ as a gate insulator of TFT are presented in this paper paperaper

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.405-411
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• 2010

A 5kW class SOFC cogeneration system consisted of a hot box part, a cold BOP (balance of plant) part, and a hot water reservoir. The hot box part contained a stack, a fuel reformer, a catalytic combustor, and heat exchangers. A cold BOP part was composed of blowers, pumps, a water trap, and system control units. A 5kW stack was designed to integrate 2 sub-modules. In this paper, the 5kW class SOFC system was operated using 2 short stacks connected in parallel to test the sub-module and the system. A short stack had 15 cells with $15{\times}15 cm^2$ area. When a natural gas was used, the total power was about 1.38 kW at 120A. Because the sub-modules were connected in parallel and current was loaded using a DC load, voltages of sub-modules were same and the currents were distributed according to the resistance of sub-modules. The voltage of the first stack was 11.46 V at 61A and the voltage of the second stack was 11.49V at 59A.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.9-17
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• 1996

Plasma enhanced chemical vapor deposition (PECVD) allows low temperature processing and so it is widely used, but it causes instability of devices due to serious amount of impurities within the film. In this paper, electrical and chemical characteristics of the PECVD oxynitride film formed by different N$_{2}$O to N$_{2}$O+NH$_{3}$ gas ratio is studied. It has been found that hydrogen concentration of PECVD oxynitride film was decreased from 4.25*10$^{22}$ [cm$^{-2}$ ] to 1.18*10$^{21}$ [cm$^{-2}$ ] according to the increase of N$_{2}$O gas. It was also found that PECVD oxynitride films have low trap density in the oxide and interface in comparison with PECVD nitroxide films, and has higher refractive index and capacitance than oxide films. In particular, oxynitride film formed in gas ratio of N$_{2}$O/(N$_{2}$O+NH$_{3}$)= 0.88 shows increased capacitance and decreased leakage current due to small portion of hydrogen in oxide and the accumulation of nitrogen about 4[atm.%] at the interface.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.361-364
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• 2009

KEPRI has studied planar type SOFC stacks using anode-supported single cells and kW class co-generation systems for residential power generation. A 1kW class SOFC system consisted of a hot box part, a cold BOP part and a water reservoir. A hot box part contains a SOFC stack made up of 48 cells with $10{\times}10cm^2$ area and ferritic stainless steel interconnectors, a fuel reformer, a catalytic combustor and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation. A cold BOP part was composed of blowers, pumps, a water trap and system control units. When a 1kW class SOFC system was operated at $750^{\circ}C$ with hydrogen, the stack power was 1.2kW at 30 A and 1.6kW at 50A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about 1.3kW with hydrogen and 1.2kW with city gas respectively. The system also recuperated heat of about 1.1kW by making hot water. Recently KEPRI developed stacks using $15{\times}15cm^2$ cells and tested them. KEPRI will develop a 5 kW class CHP system using $15{\times}15cm^2$ stacks by 2010.