• New & Renewable Energy
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• v.8 no.1
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• pp.24-34
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• 2012

The main issue of boron doped p-type czochralski-grown silicon solar cells is the degradation when they are exposed to light or minority carriers injection. This is due to the meta-stable defect such as boron-oxygen in the Cz-Si material. Although a clear explanation is still researching, recent investigations have revealed that the Cz-Si defect is related with the boron and the oxygen concentration. They also revealed how these defects act a recombination centers in solar cells using density function theory (DFT) calculation. This paper reviews the physical understanding and gives an overview of the degradation models. Therefore, various methods for avoiding the light-induced degradation in Cz-Si solar cells are compared in this paper.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.133-138
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• 2017

We investigated the interface defect engineering and reaction mechanism of reduced transition layer and nitride layer in the active plasma process on 4H-SiC by the plasma reaction with the rapid processing time at the room temperature. Through the combination of experiment and theoretical studies, we clearly observed that advanced active plasma process on 4H-SiC of oxidation and nitridation have improved electrical properties by the stable bond structure and decrease of the interfacial defects. In the plasma oxidation system, we showed that plasma oxide on SiC has enhanced electrical characteristics than the thermally oxidation and suppressed generation of the interface trap density. The decrease of the defect states in transition layer and stress induced leakage current (SILC) clearly showed that plasma process enhances quality of $SiO_2$ by the reduction of transition layer due to the controlled interstitial C atoms. And in another processes, the Plasma Nitridation (PN) system, we investigated the modification in bond structure in the nitride SiC surface by the rapid PN process. We observed that converted N reacted through spontaneous incorporation the SiC sub-surface, resulting in N atoms converted to C-site by the low bond energy. In particular, electrical properties exhibited that the generated trap states was suppressed with the nitrided layer. The results of active plasma oxidation and nitridation system suggest plasma processes on SiC of rapid and low temperature process, compare with the traditional gas annealing process with high temperature and long process time.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.162-167
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• 2010

We investigated the adsorption and desorption characteristics of benzene molecules on $Si(001)-2{\times}n$ surfaces using a variable-low temperature scanning tunneling microscopy. When benzene was adsorbed on a $Si(001)-2{\times}n$ surface at a low coverage, five distinct adsorption configurations were found: tight-binding (TB), standard-butterfly (SB), twisted-bridge, diagonal-bridge, and pedestal. The TB and SB configurations were the most dominant ones and could be reversibly interconverted, diffused, and desorbed by applying an electric field between the tip and the surface. The population ratios of the TB and SB configurations were affected by the benzene coverage: at high coverage, the population ratio of SB increased over that of TB, which was favored at low coverage. The desorption yield decreased with increasing benzene coverage and/or density of vacancy defect. These results suggest that the interaction between the benzene molecules is important at a high coverage, and that the vacancy defects modify the adsorption and desorption energies of the benzene molecules on Si(001) surface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.397-404
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• 2006

Effects of surface defect distribution on flame instability during flame-surface interaction are experimentally investigated. To examine chemical quenching phenomenon which is caused by radical adsorption and recombination processes on the surface, thermally grown silicon oxide plates with well-defined defect density were prepared. ion implantation technique was used to control the number of defects, i.e. oxygen vacancies. In an attempt to preferentially remove oxygen atoms from silicon dioxide surface, argon ions with low energy level from 3keV to 5keV were irradiated at the incident angle of $60^{\circ}$. Compositional and structural modification of $SiO_2$ induced by low-energy $Ar^+$ ion irradiation has been characterized by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). It has been found that as the ion energy is increased, the number of structural defect is also increased and non-stoichiometric condition of $SiO_x({\le}2)$ is enhanced.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.958-967
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• 2023

This work studies the defect features in a dilute FeMnNi alloy by an Object Kinetic Monte Carlo (OKMC) model based on the "grey-alloy" method. The dose rate effect is studied at 573 K in a wide range of dose rates from 10^-8 to 10^-4 displacement per atom (dpa)/s and demonstrates that the density of defect clusters rises while the average size of defect clusters decreases with increasing dose rate. However, the dose-rate effect decreases with increasing irradiation dose. The model considered two realistic mechanisms for producing <100>-type self-interstitial atom (SIA) loops and gave reasonable production ratios compared with experimental results. Our simulation shows that the proportion of <100>-type SIA loops could change obviously with the dose rate, influencing hardening prediction for various dose rates irradiation. We also investigated ways to compensate for the dose rate effect. The simulation results verified that about a 100 K temperature shift at a high dose rate of 1×10^-4 dpa/s could produce similar irradiation microstructures to a lower dose rate of 1×10^-7 dpa/s irradiation, including matrix defects and deduced solute migration events. The work brings new insight into the OKMC modeling and the dose rate effect of the Fe-based alloys.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.231-237
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• 1996

Defect equilibrium equations were modelled, and the relations of P $o_2$, venus x were derived using the mass action law. The dominant defect species active in a specified region were determined by fitting the curve of experimental data to the calculated curve of log P $o_2$, versus log x for each theoretical model. The calculated curve for (2:1:2) and (Er')$^{x}$ in the hyperstoichiometric $U_{1-y}$E $r_{y}$ $O_{2＋x}$ and that for (2Er'quot;)$^{x}$ $_{dec}$ in the hypostoichiometric $U_{1-y}$E $r_{y}$ $O_{2－x}$ are in good agreement with the present experimental results. The sintering behavior of Er-doped U $O_2$ is observed with erbium content in oxidizing and reducing atmospheres. For sintering in oxidizing atmosphere, sintered density decreases as increasing y in $U_{1-y}$E $r_{y}$ $O_{2＋x}$. However, in hydrogen atmosphere, sintered density decreases as increasing y at lower erbium content but the density increases again above y=0.10. In oxidizing sintering conditions, the formation of (Er'U')$^{x}$ clusters hinders the diffusion of cations, and hence the sinterability of Er-doped U $O_2$ decreases. In reducing atmosphere of Er-doped U $O_2$ for higher Er concent, the oxygen vacancies make (Er')$^{x}$ cluster decompose by charge compensation and the concentration of mobile cations increases, thereby improving the sinterability.ntration of mobile cations increases, thereby improving the sinterability.ability.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.52-59
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• 1989

The reliability of the thin thermal oxide was investigated by using constant current stress method. Polysilicon gate MOS capacitors with oxide thickness range of 20-25nm were used in this experiment. Automatic measurement and statistical data analysis which were essential in reliability evaluation of VLSI process preformed by HP 9000 computer. Based on TDDB results, defect density, breakdown charge (Qbd) and lifetime of oxide film were evaluated. According to the polarity of the stress, some different characteristics were shown. Defect density was 62/$cm^2$ at negative gate injection. The value of Qbd was about 30C/$cm^2$ at positive gate injection, and about 21C/$cm^2$ at negative. The current density acceleration factor was 1.43$cm^2$/A for negative gate injection, and 1.25$cm^2$/A for positive gate injection.

• 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.