• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.118-119
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• 2013

High power, short wavelength red laser diodes (LDs) have attracted significant interests in a variety of fields due to their advantages in terms of reliability, compactness and cost. The higher brightness for human eyes is required, the shorter wavelength like 630 nm is necessary with higher output power. In this respect, LDs are promising as alternative candidates of gas or dye lasers for such applications due to their small size, high optical/electrical power conversion efficiency, robustness and so on. The crystalline quality of GaInP-AlGaInP multiple quantum wells (MQWs) and AlInP cladding layers is a crucial part in the device performance of GaInP red LDs. Here, we first investigated the effect of Si diffusion on the optical properties of GaInP-AlGaInP MQWs grown with different growth temperatures. Secondary ion mass spectroscopy (SIMS) measurements revealed that both the Mg and Si diffusion into MQW active region was significant. To reduce such diffusion, we employed undoped Mg and Si diffusion barrier and could improve the properties.Without both Mg and Si diffusion barriers, no lasing emission was observed. However, lasing emission was observed clearly for the red LDs with both Mg and Si diffusion barriers. We then investigated the temperature dependent optical properties of MQW layers grown with different well thicknesses (6, 8 and 10 nm). When the well thickness was 10 nm, the better crystalline quality was obtained. However, the observed LD performances were similar, probably due to the defects and impurities in the AlGaInP layer. Further investigation with the detailed analyses will be presented later.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.197-202
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• 2023

Calcium fluoride (CaF₂) single crystal is applied to numerous industrial applications, especially for optical uses. To have excellent optical transmission properties, however, CaF₂ crystals should be carefully fabricated through liquid-phase crystal growth techniques. In this study, as one of the early stage research activities to grow CaF₂ crystals with a good transmittance at the ultraviolet wavelength range, computational thermodynamic models were provided to deepen the understanding of the crystal growing processes of CaF₂ under various conditions. To remove point defects and oxygen impurities in the grown CaF₂ crystals, the system was thermodynamically evaluated to get optimal process conditions. From the reviews of previous experimental studies, computational thermodynamic approaches were found to be an effective and powerful tool to understand the meaning of the crystal growth processes and to obtain optimal process conditions.

• Journal of the Korea Computer Industry Society
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• v.6 no.2
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• pp.357-364
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• 2005

The prefabricated type used generally in Korea to join cable runs on new installations or to repair broken Cable runs on existing installations, because installation is very simple and save time. This type is a permanent, shielded and submersible cable joint for direct burial or vault application. It confirms to the requirements of IEEE std. 404-1993 by factory testing, but many problems of insulated cable systems are caused by internal defects of the joint part which have to be mounted ensile. Faults arise from impurities or voids. A suitable solution for a monitoring of cable joints during the after-laying test and service is partial discharge detection. Specimen obtained 1mm thickness from the insulation of real power cable and cable joint. <중략>The partial discharges are measured to determine their time dependence for 60 minutes and the influence of applied electrical stress under 30kV. $\Phi-q-n$ properties were measured using detection impedance, high pass filter and computerized data acquisition system. Statistic Value like maximum charge, repetition rate, average charge, etc. are calculated. It is possible to quantitative analysis of $\Phi-q-n$ properties from this statistic value and pattern analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.248-248
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• 2011

ZnO was grown on a Au-catalyzed Si(100) substrate by using a simple vapor phase transport (VPT) with a mixture of zinc oxide and graphite powders. The ZnO grown at 800$^{\circ}C$ had a soccer ball structure with diameters of <500 nm. The ZnO soccer ball structure was, for the first time, observed in this work. The optical properties of the ZnO soccer balls were investigated by photoluminescence (PL). In the room-temperature (RT) PL of the ZnO soccer balls, a strong near-band-edge emission (NBE) and a weak deep-level emission were observed at 3.25 and 2.47 eV (green emission), respectively. The weak deep-level emission (DLE) at around 2.47 eV (green emission) is caused by impurities and structural defects. The FWHM of the NBE peak from the ZnO soccer balls was 110 meV. In addition, the PL intensity ratio of the NBE to DLE was about 4. The temperature-dependent PL was also carried out to investigate the mechanism governing the quenching behavior of the PL spectra.

• Journal of the Korea Computer Industry Society
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• v.6 no.2
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• pp.279-286
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• 2005

The prefabricated type used generally in Korea to join cable runs on new installations or to repair broken Cable runs on existing installations, because installation is very simple and save time. This type is a permanent, shielded and submersible cable joint for direct burial or vault application. It confirms to the requirements of IEEE std. 404-1993 by factory testing, but many problems of insulated cable systems are caused by internal defects of the joint part which have to be mounted ensile. Faults arise from impurities or voids. A suitable solution for a monitoring of cable joints during the after-laying test and service is partial discharge detection. <중략> $\Phi-q-n$ properties were measured using detection impedance, high pass filter and computerized data acquisition system. Statistic Value like maximum charge, repetition rate, average charge, etc. are calculated. It is possible to quantitative analysis of $\Phi-q-n$ properties from this statistic value and pattern analysis.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.105-112
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• 2004

A waste container, one of the key components of a multi-barrier system in a potential high level radioactive waste (HLW) repository in Korea ensures the mechanical stability against the lithostatic pressure of a deep geologic medium and the swelling pressure of the bentonite buffer. Also, it delays potential release of radionuclides for a certain period of time, before it is corroded by intruding impurities. Even though the material of a waste container is carefully chosen and its manufacturing processes are under quality assurance processes, there is a possibility of initial defects in a waste container during manufacturing. Also, during the deposition of a waste container in a repository, there is a chance of an incident affecting the integrity of a waste container. In this study, the appropriate Features, Events, and Processes(FEP's) to describe these incidents and the associated scenario on radionuclide release from a container to the biosphere are developed. Then the total system performance assessment on the Initial waste Container Failure (ICF) scenario was carried out by the MASCOT-K, one of the probabilistic safety assessment tools KAERI has developed. Results show that for the data set used in this paper, the annual individual dose for the ICF scenario meets the Korean regulation on the post closure radiological safety of a repository.

• Conservation Science in Museum
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• v.6
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• pp.3-10
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• 2005

In the course of preparing for the transfer of the Boshin-gak Bell, which was designated as Treasure No. 2, due to the transfer of the National Museum of Korea, the current internal cracks and defects in the founding of the bell were examined in order to verify its solidity through γ-ray penetration via ⁶⁰Co. The bell's compositions were also examined with x-ray fluorescence spectroscopy. The result showed that the bell had 65.2% cracks when viewed from the horizontal direction and 62.5% cracks when viewed from the vertical direction. The cracks had approximately 5cm depth. In addition, the result of examining the composition of the bell revealed that it was made of 89~92% copper and 7.5~10.5% tin as well as traces of impurities including 0.1~0.3% lead and not more than 0.1% iron, manganese, etc.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.229-232
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• 2003

A waste container, one of the key compartments in a multi-barrier system for a potential high level radioactive waste (HLW) repository in Korea ensures the mechanical stability against the lithostatic pressure of a deep geologic strata and the swelling pressure of the bentonite buffer. Also, it prohibits potential release of radionuclides for a certain period of time. before it is corroded by impurities. Even though the materials of a waste container is carefully chosen and all manufacturing processes are under heavy quality assurance, there might be a slight chance of intial defects in a waste container. Also, during the deposition of a waste container in a repository, there might be a chance of an incident affecting the integrity of a waste container. In this study, the FEP's and the scenarios over radiological impact of a potential initial waste container defect was developed. Then the total system performance assessment on this initial waste container failure (ICF) scenario was carried out by the MASCOT-K, one of the probabilistic safety assessment tools KAERI has developed. Results show that for the data set studied in this paper, the annual individual dose by the ICF scenario well meets the KINS regulation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.334-340
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• 1997

Electric and dielectric properties of the $SrTiO_3$films have been studied. The influence of impurities on $SrTiO_3$ films was evaluated to reduce the leakage current density. Acceptor doping, with a small concentration of Fe or Cr, has led to a substantial improvement to $10^{-9}$ order in the leakage current density. The experimental results can be explained by a model in which oxygen vacancies are the key defects responsible for the leakage current. The $SrTiO_3$ film 200 nm in thickness with 5 mol% excess SrO fabricated in $Ar/O_2$ at $550^{\circ}C$ obtained the lowest leakage current density $1.0 {\times} 1.0 A/\textrm{cm}^2$. The improved results can be introduced into the capacitor dielectric of giga bit DRAM memories.

• Congress of the korean instutite of fire investigation
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• 2010.12a
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• pp.63-79
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• 2010

It is found to the arc trace on the junction termination of 345kV cable. According to the analysis of the cable material is judged to be good. Manufacturing and design problems are not considered. In construction defects, it was estimated to the low level of insulation oil. In the majority of the arc trace appeared XLPE is found. However, there is no Soots mark, yellow band has not been confirmed, not associated with a radial arc of the spider leg is not evidence. In other opinions, void, contamination or jut are not found on the inside of XLPE. Thus, by the attachment of the impurities in surface of XLPE insulation is judged to the breakdown.