• Current Photovoltaic Research
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• v.2 no.2
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• pp.59-62
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• 2014

Minority carrier diffusion length is one of the most important parameters of solar cells, especially for short circuit current density (Jsc). In this report, we proposed the calculating method of the minority carrier diffusion length ($L_n$) in CIGS solar cells through biased quantum efficiency (QE). To verify this method's reliability, we chose two CIGS samples which have different grain size and calculated $L_n$ for each sample. First of all, we calculated out that $L_n$ was 56nm and 97nm for small and large grain sized-cell through this method, respectively. Second, we found out the large grain sized-cell has about 7 times lower defect density than the small grain sized-cell using drive level capacitance profiling (DLCP) method. Consequently, we confirmed that $L_n$ was mainly affected by the micro-structure and defect density of CIGS layer, and could explain the cause of Jsc difference between two samples having same band gap.

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.26-32
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• 1997

Quartz single crystals were grown hydrothermally and growth defects such as dislocations, etch channels and impurities were examined. Growth rates were 0.25-0.65 mm/day under the growth conditions of following. 1. Mineralizer: $4wt.\%$ NaOH. 2. Growth temperature: $340-360^{\circ}C$. 3. Temperature gradient: $20-40^{\circ}C$. 4. Seed: ZY plate. 5. Nutrient: synthetic quartz. Defects of the quartz which was grown with optical grade synthetic nutrient, low dislocation density seed and horizontal seed setting technique were as follows. 1. Dislocation density: 20.0 each/$cm^2$. 2. Etch channel density: 5.0 each/$cm^2$ (1st grade by IEC 758 standard). 3. Impurity (larger than 10$\mu$) concentration: 2.4 each/$cm^3$ (Ia grade by IEC 758 standard). 4. Alpha value: 0.019 (A grade by IEC 758 standard).

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.94-100
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• 2004

Gas porosity which is a common defect in aluminum alloy casting, is also thought to be severer in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process variables such as the melt treatment, the cooling rate and pouring temperature on the density and mechanical properties in A356.2 castings with simple bar shape. The density of grain refined specimen was slightly lower than that of degassed one, but was higher than that of no treated one and that of shot ball packed specimen was higher than the other specimens. The tensile strength and elongation were in the ranges of $200{\sim}230MPa$ and $0.5{\sim}1.5%$ respectively. The density and hardness of lost foam cast specimens decreased with increase in pouring temperature.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.166-171
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• 2016

Nickel silicide is main issue in Polycrystalline silicon Thin Film Transistor (TFT) which is made by Metal Induced Lateral Crystallization (MILC) method. This Nickel silicide acts as a defect center, and this defect is one of the biggest reason of the high leakage current. In this research, we fabricated polycrystalline TFTs with novel method called Edge Cut (EC). With this new fabrication method, we assumed that nickel silicide at the edge of the channel region is reduced. Electrical properties are measured and trap state density also calculated using Levinson & Proano method.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.267-273
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• 2001

In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.108-117
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• 2004

In this paper, a measuring NDT(nondestructive testing) system using RUS(Resonant Ultrasound Spectroscopy) was built for nondestructive evaluation of the flaw in a ceramic Ferrule. The principle of RUS is that the mechanical resonant frequency of the materials depends on density, and the coefficient of elasticity. The RUS system is the measuring which is to exite specimen and to inspect the difference of natural frequency pattern between acceptable specimen and specimen which has some defects. RUS system is configured of spectrum analyzer, power amplifier, PZT sensor and support frame. For defect evaluation by the RUS, we performed to measure natural frequency of Ferrule, both acceptable and cracked. In the case of Ferrule, the resonant frequency of cracked-Ferrule existed to higher frequency band than acceptable-Ferrule.

• Journal of Veterinary Clinics
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• v.14 no.2
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• pp.352-356
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• 1997

5 years Poodle was referred to the Veterinary Teaching Hospital, Chonnam National University in January 1997, with progressive swelling on the rear xiphoid process after cesarean section last year in local-vet clinic. Physical, radiographic, ultrasonographic and intraoperative findings that were obtained from this case were as follow; Physical findings were known as no pain, no fever in the hernia] sal at palpation. Radiographic findings revealed the decreased density of swelling contents more than peritoneum and did not identify the abdominal wall defect line. Ultrasonographic findings showed abdominal wall defect line of 3mm and intra-abdominal originated fat contents with mixed echo(hypoechoic). During the operation, falciform ligament into the hernial sac was observed and not excised, manipulated back into the cavity. The dog was given an herniorraphy with no recurrence and infection.

• Transactions on Electrical and Electronic Materials
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• v.10 no.6
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• pp.189-192
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• 2009

The leakage current in a CMOS image sensor (CIS) can have various origins. Leakage current investigations have focused on such things as cobalt-salicide, source and drain scheme, and shallow trench isolation (STI) profile. However, there have been few papers examining the effects on leakage current of nitride stringers that are formed by gate sidewall etching. So this study reports the results of a series of experiments on the effects of a nitride stringer on real display images. Different step heights were fabricated during a STI chemical mechanical polishing process to form different nitride stringer sizes, arsenic and boron were implanted in each fabricated photodiode, and the doping density profiles were analyzed. Electrons that moved onto the silicon surface caused the dark leakage current, which in turn brought up the speckle defect on the display image in the CIS.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.308-312
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• 2016

2차원 화합물 반도체인 GaS single tetralayer에 존재하는 vacancy defect의 원자구조 및 전자구조 특성을 제일원리계산을 이용하여 연구하였다. 고립된 Ga과 S vacancy를 모델링하기 위해, GaS $4{\times}4$ supercell을 이용하였고 각 vacancy에 대해 symmetry-preserving 구조와 broken symmetry 구조들의 에너지를 계산하여 가장 안정한 결함 원자 구조를 결정하였다. Ga-rich, S-rich condition에서의 formation energy 계산을 통해 vacancy 구조의 생성 가능성을 예측하였다. 안정한 vacancy 구조들에 대해 projected density of states (PDOS)를 clean GaS의 PDOS와 비교 분석함으로써 vacancy에 의한 defect states들을 찾고, 결과적으로 나타나는 전자구조 특성의 변화를 규명하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.05a
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• pp.61-61
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• 2003

It is important to know SIze distribution of defects In electroplated trivalent chrome layers because it significantly influences on performance of the layers. Most of the nano-scale defects are able to be introduced by hydrogen evolution during the plating. Little information is available on the nano-size defects. In this study, SANS was applied to determine the size distribution of nano-scale defects in the trivalent chrome layers prepared in a formate bath. The defect size and distribution was dependent upon plating conditions such as current density and applied voltage. SANS is one of useful techniques to determine the nano-scale defect in the electroplated layers.