• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.1 no.2
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• pp.74-81
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• 1987

The reduction in dielectric strength of insulating polymer material when applying electric field is known to be substantial due to the trapped carrier effect. In this study, the carrier property of Biaxially-Drawn polypropylene, which has superior heat-resistance compared to ordinary one, is examined to improve electrical characteristics by measuring TSC spectra as a function of electric field applied to a sample of ($50{\mu}m$) thickness film. The TSC spectra in the temperature range of 303-413(K) and electric field of 2-80(MV/m) have shown no observable effect below 12(MV 1m) but TSC currents of Hetero-and Homo-peaks formed from trapped space charger and space charger injected from electrode have been observed above that point, which seems eventually lead to dielectric breakdown. Finally, this study has shown the superior dielectric proporty of Biaxially-Drawn polypropylene film compared to the non-oriented one for electrical insulation.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.1-6
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• 2015

We investigated green phosphorescent organic light-emitting diodes with stepwise doping to improve efficiency roll-off and operational lifetime by efficient distribution of triplet excitons. The host material which was 4,4,N,N'-dicarbazolebiphenyl (CBP) of bipolar characteristic that can control the carrier in emitting layer (EML). When the EML devided into four parts with different doping concentration, each devices shows various efficiency roll-off and lifetime enhancement. The distribution of the carrier and excitons in the EML can be confirmed by using stepwise doping structure. The properties of device C exhibited luminous efficiency of 51.10 cd/A, external quantum efficiency of 14.88%, respectively. Lifetime has increased 73.70% compared to the reference device.

• Journal of Navigation and Port Research
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• v.38 no.6
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• pp.577-583
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• 2014

A ship-to-ship (STS) lightering operation takes place in order to transfer cargo (e.g. crude oil or petroleum products) between an ocean-going ship and a service ship alongside it. Instrumental measurements to accurately determine the relative speeds and distances during the approach between the vessels would benefit the operational safety and efficiency. A velocity information GPS (VI-GPS) system, which uses the instantaneous velocity measures from carrier-phase Doppler measurement, has been applied in a field observation onboard a service ship (Aframax tanker) approaching a ship-to-be-lightered (VLCC) in open waters. This article proposes to apply VI-GPS as the input sensor to a guidance and decision-support system aiming to provide accurate velocity information to the officer in charge of an STS operation. A method for precise velocity measurement using VI-GPS was described and the measurement results were compared each other with the results of Voyage Data Recorder (VDR) and VI-GPS that showed the concept of a guidance and decision-support system applying VI-GPS with the field test results during STS operations. Also, it turned out that VI-GPS has sufficient accuracy to serve as an input sensor from the field test results.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.462-462
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• 2014

The effect of rear passivation for passivated emitter and rear cell (PERC) using ozone and H2O oxidant of atomic layer deposited (ALD) Al2O3 was studied by post-annealing in N2 and forming gas ambients. Rear surface of PERC solar cell was passivated by Al2O3 grown by ALD with ozone and H2O oxidant. Al2O3 grown by ALD with ozone oxidant has been known to have many advantages, such as lower interface defects, low leakage current density. Its passivation quality is better than Al2O3 with H2O. Al2O3 layer with 10 nm and 20 nm thickness was grown at $150^{\circ}C$ with ozone oxidant and at $250^{\circ}C$ with H2O oxidant. And then each samples were post-annealled at $450^{\circ}C$ in N2 ambients and at $850^{\circ}C$ in forming gas ambients. The passivation quality was investigated by measuring the minority carrier lifetime respectively. We examined atomic layer deposited Al2O3 such as growth rate, film density, thickness, negative fixed charge density at AlOx/Si interface, and reflectance. The influences of process temperature and heat treatment were investigated using Sinton (WCT-120) by Quasi-Steady State Photoconductance (QSSPC) mode. Ozone-based ALD Al2O3 film shows the best carrier lifetime at lower deposition temperature than H2O-based ALD.

• Current Photovoltaic Research
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• v.4 no.4
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• pp.150-154
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• 2016

Mg and In co-doped ZnO (MIZO) thin films with transparent conducting characteristics were successfully prepared on glass substrates by RF magnetron sputtering technique. The Influence of different substrate temperature (from RT to $400^{\circ}C$) on the structural, morphological, electrical, and optical properties of MIZO thin films were investigated. The MIZO thin film prepared at the substrate temperature of $350^{\circ}C$ showed the best electrical characteristics in terms of the carrier concentration ($4.24{\times}10^{20}cm^{-3}$), charge carrier mobility ($5.01cm^2V^{-1}S^{-1}$), and a minimum resistivity ($1.24{\times}10^{-4}{\Omega}{\cdot}cm$). The average transmission of MIZO thin films in the visible range was over 80% and the absorption edges of MIZO thin films were very sharp. The bandgap energy of MIZO thin films becomes wider from 3.44 eV to 3.6 eV as the substrate temperature increased from RT to $350^{\circ}C$. However, Band gap energy of MIZO thin film was narrow at substrate temperature of $400^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.196-196
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• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbled appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. Based on the graphene's high carrier mobility, high frequency graphene field effect transistors have been developed. Graphene is useful for photonic components as well as for the applications in electronic devices. Graphene's unique optical properties allowed us to develop ultra wide-bandwidth optical modulator, photo-detector, and broadband polarizer. Graphene can support SPP-like surface wave because it is considered as a two-dimensional metal-like systems. The SPPs are associated with the coupling between collective oscillation of free electrons in the metal and electromagnetic waves. The charged free carriers in the graphene contribute to support the surface waves at the graphene-dielectric interface by coupling to the electromagnetic wave. In addition, graphene can control the surface waves because its charge carrier density is tunable by means of a chemical doping method, varying the Fermi level by applying gate bias voltage, and/or applying magnetic field. As an extended application of graphene in photonics, we investigated the characteristics of the graphene-based plasmonic waveguide for optical signal transmission. The graphene strips embedded in a dielectric are served as a high-frequency optical signal guiding medium. The TM polarization wave is transmitted 6 mm-long graphene waveguide with the averaged extinction ratio of 19 dB at the telecom wavelength of $1.31{\mu}m$. 2.5 Gbps data transmission was successfully accomplished with the graphene waveguide. Based on these experimental results, we concluded that the graphene-based plasmonic waveguide can be exploited further for development of next-generation integrated photonic circuits on a chip.

• YAKHAK HOEJI
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• v.36 no.2
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• pp.159-166
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• 1992

A neoglycolipid, N-stearyl lactobionamide(N-SLBA) was synthesized and the incorporation of the neoglycolipid into liposomes was achieved in order to prepare neo-galactosylated liposome as potential drug carrier for active targeting to galactose receptor existing cell and tissue. N-SLBA was synthesized by the covalent linkage between carboxyl group of lactobionic acid and amino group of stearylamine(SA). The yield of N-SLBA was about 52.3%. It was identified with $1650\;cm^{-1}$ in IR chart, 7.5 ppm in NMR spectra, $61^{\circ}C$ endothermic peak in DSC heating curve. Surface-modified large unilamellar vesicle with galactose(N-SLBA-LUV) could be prepared with N-SLBA by reverse evaporation method. N-SLBA-LUV was identified by TEM and measuring of membrane function. The maximum amount of N-SLBA incorporated into liposome is up to about 15 mol%. Compared with control liposome (SA-LUV), N-SLBA-LUV showed lower encapsulation efficiency of MTX. It might due to the loss of positive surface charge of stearylamine. N-SLBA-LUV was similar to SA-LUV in aspect of osmotic behavior. N-SLBA-LUV prepared with N-SLBA would be expected to be a good carrier for active targeting to galactose receptor existing cell and tissue.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.575-582
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• 2000

The Electrical conduction and optical properties of Ta$_{2}$/O$_{5}$ thin films as the insulators in DRAM capacitors were studied. Liquid Ta/sib 2//O sub 5/ were prepared by a sol-gel processing and multiple layers were applied by spin-coating up to thickness of 800$\AA$. At annealing temperature of 300~$600^{\circ}C$ the electrical conduction and specific dielectric constant were discussed the behaivor of carrier were observed by the Thermally Stimulated Current (TSC) at the temperature range of 30~23$0^{\circ}C$. At annealing temperature of 300~$600^{\circ}C$ the samples were found to be amorphous below $600^{\circ}C$ and crystalline over it. The electrical strength was about 2.2 MV/cm at 40$0^{\circ}C$. In spite of noncrystallization over 50$0^{\circ}C$ the increasing of leakage current due to pinholes and increasing creak. The refractive index was obtained maximum (2.2) at 40$0^{\circ}C$. The dielectric constant was obtained maximum(18.6) at 40$0^{\circ}C$. TSC was observed one peak at the temperature range of 30~23$0^{\circ}C$ from sample at 40$0^{\circ}C$. In the case of collecting voltage the peak size is decreased in proportion to collecting voltage and then the peak may be thought carrier to be a ionic space charge.e.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.120-125
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• 2005

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. Among the accidents and failures that occur during concrete construction, many are formwork failures which usually happen at the time concrete is being placed. In constructions site, pipe supports are usually used as shores which are consisted of the slab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies fire of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KS F 8001. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.430-430
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• 2012

The surface recombination velocity of the silicon solar cell could be reduced by passivation with insulating layers such as $SiO_2$, SiNx, $Al_2O_3$, a-Si. Especially, the aluminium oxide has advantages over other materials at rear surface, because negative fixed charge via Al vacancy has an additional back surface field effect (BSF). It can increase the lifetime of the hole carrier in p-type silicon. The aluminium oxide thin film layer is usually deposited by atomic layer deposition (ALD) technique, which is expensive and has low deposition rate. In this study, ICP-assisted reactive magnetron sputtering technique was adopted to overcome drawbacks of ALD technique. In addition, it has been known that by annealing aluminium oxide layer in nitrogen atmosphere, the negative fixed charge effect could be further improved. By using ICP-assisted reactive magnetron sputtering technique, oxygen to nitrogen ratio could be precisely controlled. Fabricated aluminium oxy-nitride (AlON) layer on silicon wafers were analyzed by x-ray photoelectron spectroscopy (XPS) to investigate the atomic concentration ratio and chemical states. The electrical properties of Al/($Al_2O_3$ or $SiO_2/Al_2O_3$)/Si (MIS) devices were characterized by the C-V measurement technique using HP 4284A. The detailed characteristics of the AlON passivation layer will be shown and discussed.