• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.278-284
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• 2009

The global force and interaction body force density were evaluated in permanent magnets by using the virtual air-gap scheme incorporating the finite-element method. Until now, the virtual air-gap concept has been successfully applied to calculate a contact force and a body force density in soft magnetic materials. These force calculating methods have been called as generalized methods such as the generalized magnetic charge force density method, the generalized magnetizing current force density method, and the generalized Kelvin force density method. For permanent magnets, however, there have been few research works on a contact force and a force density field. Unlike the conventional force calculating methods resulting in surface force densities, the generalized methods are novel methods of evaluating body force density. These generalized methods yield the actual total force, but their distributions have an irregularity, which seems to be random distributions of body force density. Inside permanent magnets, however, a smooth pattern was obtained in the interaction body force density, which represents the interacting force field among magnetic materials. To evaluate the interaction body force density, the intrinsic force density should be withdrawn from the total force density. Several analysis models with permanent magnets were tested to verify the proposed methods evaluating the interaction body force density and the contact force, in which the permanent magnet contacts with a soft magnetic material.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.463-466
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• 2008

We report a method to increase the surface area of the titania films used as the anodes of dye-sensitized solar cells (DSSCs) by applying additional titania-coating. The modification was achieved by spin-coating a coating solution that contained a surfactant with a titania source onto the titania electrodes, followed by calcination. Previous similar attempts without a surfactant all reported decreased surface areas. We fabricated DSSCs by using the modified titania films as the anode and measured their performances. The increased surface area increased the amount of adsorbed dyes, which resulted in increased current densities. At the same time, the titania-coating increased both the open-circuit voltage and the current density by reducing the charge-recombination rates of the injected electrons, similar to the results of literatures. Therefore, our method shows an additional mechanism to increase the current density of DSSCs in addition to the other mechanisms of surface modifications with titania-coatings.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1438-1440
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• 1998

In this work, simultaneous measur of space charge and conduction current was c out in LDPE with air gap by Pulsed-Electro-Aco Method. Also, effect of long time charging at con electric field on the formation of space charge conduction was investigated. From the experim results. we knew that the homo space charge formed near the dielectric surfaces and moving the bulk of dielectric as the electric field elevated. This was related with the deep traps b carriers and de trapping by Poole-field lowering conduction current was coincident with the Pool emission. From the long time charging experimen obtained the results that the negative space was moving into the dielectric bulk as the cha continued and the positive space charge accumulated at upper surface of LDPE.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.111-115
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• 2015

To improve the efficiency of the Si solar cell, high minority carrier life time is required. Therefore, the passivation technology is important to eliminate point defects on the silicon surface, causing the loss of minority carrier recombination. PECVD or post-annealing of thermally-grown $SiO_2$ is commonly used to form the passivation layer, but a high-temperature process and low thermal stability is a critical factor of low minority carrier lifetime. In this study, atomic layer deposition was used to grow the $Al_2O_3$ passivation layer at low temperature process. $Al_2O_3$ was selected as a passivation layer which has a low surface recombination velocity because of the fixed charge density. For the high charge density, an improved minority carrier lifetime, and a low surface recombination, nitrogen was doped in the $Al_2O_3$ thin film and the improvement of passivation was studied.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.33-39
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• 1998

The BST (Ba$_{1-x}$ Sr$_{x}$TiO$_{3}$)(50/50) thin film has been grown by RF magnetron reactive sputtering and its characteristics such as crystallization, surface roughness, and electrical properties have been investigated with varying the film thickness. The crystallization and surface roughness of BST thin film are investigated by using XRD and AFM, respectively The BST thin film anealed at 800.deg. C for 2 min has pure perovskite structure and good surface roughness of 16.1.angs.. We estimate that the thickness and dielectric constant of interface layer between BST film and electrode are 3nm and 18.9, respectively, by measuring the capacitance with various film thickness. As the film thickness increases form 80nm to 240nm, the dielectric constant at 10kHz increases from 199 to 265 and the leakage current density at 200kV/cm decreases from 0.682.mu.A/cm$^{2}$ to 0.181 .mu.A/cm$^{2}$. In the case of 240nm-thick BST thin film, the charge storage density and leakage current density at 5V are 50.5fC/.mu.m$^{2}$ and 0.182.mu.A/cm$^{2}$, respectively. The values indicate that the BST thin film is a very useful dielectric material for the DRAM capacitor.or.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.4
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• pp.92-100
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• 1985

New N+N/P HLE solar cells with N+ surface charge accumulated layer in the emitter region are fabricated on the N/P Si epiwafer by incorporating high fixed positive charge density (Qss) at the Si-AR layer interface. Solar cells are classified into two categories, i.e, OCI and NCI Cell depending on AR layer, SiOl and Si3 N4/sioxynitride layer respectively. The distribution of Qss in the Si-AR layer interface is examined by C-V plot. It shows that the surface charge accumulated layer is formed more effectively in the NCI cell (Qss=1.79-1.84$\times$1012cm-2) than in the OCI cell (Qss=3.03~4.40$\times$1011 cm-2). The efficiency characteristics are evaluated under the JCR halogen lamp of 100 mw/cm2. The average (maximum) conversion efficiency for active area is 15.18 (15.46)% in the OCI cell and 16.31 (17.07)% in the NCI cell.

• Journal of Surface Science and Engineering
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• v.55 no.4
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• pp.236-246
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• 2022

Electropolishing is a surface finishing treatment that compensates for the disadvantages of the mechanical polishing process. It not only has a smooth surface, but also improves corrosion resistance. Therefore, the purpose of this investigation is to examine the corrosion resistance and electrochemical characteristics in seawater of UNS S31603 with electropolishing process time. The roughness improvement rate after electropolishing was improved by about 78% compared to before polishing, indicating that the electropolishing is effective. As a result of potential measuring of mechanical polishing and electropolishing, the potential of electropolishing was nobler than the mechanical polishing condition. As a result of calculating the corrosion current density after potentiodynamic polarization experiment with electropolishing conditions, the corrosion current density of mechanical polishing was about 6.4 times higher than that of electropolishing. After potentiodynamic polarization experiment with electropolishing conditions, the maximum damage depth of mechanical polishing was about 2.2 times higher than that of electropolishing(7 minutes). In addition, the charge transfer resistance of the specimen electropolished for 7 minutes was the highest, indicating improved corrosion resistance.

• Corrosion Science and Technology
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• v.3 no.2
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• pp.54-58
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• 2004

Effects of texture on the electrochemical behaviors of single grains in polycrystalline zinc were investigated using a capillary-based micro-droplet cell. Pontiodynamic sweeps and capacity measurements were carried out in pH 9 borate buffer solution. The cyclic voltammograms and the capacity measurements on single grains with different crystallographic orientations in polycrystalline Zn showed a strong dependence of oxide growth on crystallographic grain orientation. The total charge consumed for oxide formation and the inverse capacity increased with an increase of surface packing density of grain. suggesting the oxide formation was greater on grains with higher surface packing density.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.271-277
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• 2022

We analyzed the effects of the interface trap on the output characteristics of an inversion mode n-channel GaN Schottky barrier (SB)-MOSFET based on the N_it distribution using TCAD simulation. As interface trap number density (N_it) increased, the threshold voltage increased while the drain current density decreased. Under N_it=5.0×10¹⁰ cm^-2 condition, the threshold voltage was 3.2 V for V_DS=1 V, and the drain current density reduced to 2.4 mA/mm relative to the non-trap condition. Regardless of the N_it distribution type, there was an increase in the subthreshold swing (SS) following an increase in N_it. Under U-shaped N_it distribution, it was confirmed that the SS varied depending on the gate voltage. The interface fixed charge (Q_f) caused an shift in the threshold voltage and increased the off-state current collectively with the surface trap. In summary, GaN SB-MOSFET can be a building block for high power UV optoelectronic circuit provided the surface state is significantly reduced.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.51-55
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• 2004

Surface plasmons (SPs) are charge density oscillations that propagate along an interface between a dielectric and metal. In this paper, the electric field of SPs and the intereference of two SPs are observed by using Near-field Scanning Optical Microscope (NSOM). The excitation condition of SPs is changed as the optical tip approaches the metal surface, because the excitation condition of SPs is very sensitive to surface structures. To measure the microscope field of SPs, the distance between metal surface and optical tip must contain a specific interval.