• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2855-2860
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• 2012

The coating N-acetyl cysteine (NAC) on gold surfaces may be used to design the distribution of either gold particle adsorbed to the $ZrO_2$ surface or vice versa by adjusting the electrostatic interactions. In this study, it was performed to find out electrostatic properties of the NAC-coated-gold surface and the $ZrO_2$ surface. The surface forces between the surfaces were measured as a function of the salt concentration and pH value using the AFM. By applying the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to the surface forces, the surface potential and charge density of the surfaces were quantitatively acquired for each salt concentration and each pH value. The dependence of the potential and charge density on the concentration was explained with the law of mass action, and the pH dependence was with the ionizable groups on the surface.

• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.85-90
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• 1994

The flow properties of binder latices for paper coating were investigated, together with dynamic viscoelastic properties of latex films and electron micrographs of latices, under various conditions. The amphoteric latex, binder pigment latex and anionic latex were used in this work. The amphoteric latex has both anionic and cationic functional group on its surface. The binder-pigment with a core-shell structure has dual functions : plastic pigment and binder. The low shear viscosity of binder latices and clay slurry were measured with Brookfield vis cometer. At low-shear rates. the viscosity decreased with increasing particle size of latex. On the amphoteric latex surface, the carboxyl groups are assumed to be fully dissociated over the region of pH 9~12, but the density of negative groups seems to be increased because of the gradual decrease in the degree of dissociation of amino groups. Since the apparent particle size of latex increases with surface charge, the electroviscous effect can be observed. On the anionic latex surface, the charge density is assumed to be nearly constant above pH 8. However, below pH 8 the coagulation of particles could be observed probably because of the decrease in the charge density.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.461-465
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• 2004

This paper analysed the induced current density by electric field of human body under the 765 kV transmission line considering permittivity and conductivity. As permittivity of human body is very high as $10^6$ at 60 Hz, special numerical computation technique in Surface Charge Method(SCM) for composite media with extremely different properties is applied to reduce calculation error of induced current density and electric field inside the human body. Calculation results show that the average of the induced current density inside human body is about 3mA/$m^2$, which is less than ICNIRP criterion (10mA/$m^2$).

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.34-39
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• 2006

In high-voltage devices such as thyristor, beveling is mostly used junction termination method to reduce the surface electric field far below the bulk electric field and to expand the depletion region thus that breakdown occurs in the bulk of the device rather than at the surface. However, coating material used to protect the surface of the device contain so many charges which affect the electrical characteristics of the device. And device reliability is also affected by this charge. Therefore, it is needed to analyze the effect of surface charge on electrical characteristics of the device. In this paper, we analyzed the breakdown voltage and leakage current characteristics of the thyristor as a function of the amount of surface charge density. Two dimensional process simulator ATHENA and two-dimensional device simulator ATLAS is used to analyze the surface charge effects.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.211-211
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• 2012

Using spin-polarized density-functional theory calculations, we find that the existence of either Peierls instability or antiferromagnetic spin ordering is sensitive to hydrogen passivation near the step. As hydrogens are covered on the terrace, the dangling bond electrons are localized at the step, leading to step-induced states. We investigate the competition between charge and spin orderings in dangling-bond (DB) wires of increasing lengths fabricated on an H-terminated vicinal Si(001) surface. We find antiferromagnetic (AF) ordering to be energetically much more favorable than charge ordering. The energy preference of AF ordering shrinks in an oscillatory way as the wire length increases. This oscillatory behavior can be interpreted in terms of quantum size effects as the DB electrons fill discrete quantum levels.

• Journal of Surface Science and Engineering
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• v.47 no.5
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• pp.227-232
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• 2014

In this study, we propose the application of doping process technology for atmospheric pressure plasma. The plasma treatment means the wafer is warmed via resistance heating from current paths. These paths are induced by the surface charge density in the presence of illuminating Argon atmospheric plasmas. Furthermore, it is investigated on the high-concentration doping to a selective partial region in P type solar cell wafer. It is identified that diffusion of impurities is related to the wafer temperature. For the fixed plasma treatment time, plasma currents were set with 40, 70, 120 mA. For the processing time, IR(Infra-Red) images are analyzed via a camera dependent on the temperature of the P type wafer. Phosphorus concentrations are also analyzed through SIMS profiles from doped wafer. According to the analysis for doping process, as applied plasma currents increase, so the doping depth becomes deeper. As the junction depth is deeper, so the surface resistance is to be lowered. In addition, the surface charge density has a tendency inversely proportional to the initial phosphorus concentration. Overall, when the plasma current increases, then it becomes higher temperatures in wafer. It is shown that the diffusion of the impurity is critically dependent on the temperature of wafers.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.820-824
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• 1992

An accurate method for extracting both Si film doping concentration and front or back silicon-to-oxide fixed charge density of fully depleted SOI devices is proposed. The method utilizes the current-to-voltage and capacitance-to-voltage characteristics of both SOI NMOSFET and PMOSFET which have the same doping concentration. The Si film doping concentration and the front or back silicon-to-oxide fixed charge density are extracted by mainpulating the respective threshold voltages of the SOI NMOSFET and PMOSFET according to the back surface condition (accumulation or inversion) and the capacitance-to-voltage characteristics of the SOI PMOSFET. Device simulations show that the proposed method has less than 10% errors for wide variations of the film doping concentration and the front or the back silicon-to-oxide fixed charge density.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.42-49
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• 1992

Charge accumulation characteristics in low density polyethylene (LDPE) has been discussed based upon the internal charge distrubution measured by the pulsed electroacoustic technique. When the negative voltage with respect to earth is applied to the upper electrode, the negative charges near the anode and the positive charges near the cathode are accumulated in LDPE. Also, there was an asymmetric behavior of charge accumulation exhibiting that the charge accumulation near the anode keeps increasing whereas that near the cathode increases first and then decreases. Besides, under the present test conditions the internal charge distrubution becomes stabilized eventually. When the positive voltage with respect to earth is applied to the upper electrode, on the other hand, no such asymmetric charge accumulation was found. Therefore, it can be concluded that the heterocharges are accumulated at the surface region of LDPE subjected to high do voltages and that the begavior of charge accumulation depends on the polarity of do voltage and the position of charge accumulation.

• Journal of Surface Science and Engineering
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• v.30 no.1
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• pp.44-56
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• 1997

Influence of electrochemical etching conditions on capacitance gain of aluminium electrolytic on capacitor foil has been investigated by etching cubic textured high purity aluminum foil in dilute hydrochloric acid. Uniformly distributed etch pit tunnels on aluminum surface have been obtained by pretreatment aluminium foil in 10% NaOH solution for 5 minutes followed by electrochemical etching. Electrostatic capacitance of etched aluminium foil anodized to high voltage increased with the increase of current density, total charge, temperature and concentration of electrolyte up to maximum CV-value and then deceased. Election optical observation of the etched foil revealed that the density of etch of etch pits increased with the increase of current density and concentration of electrolyte. this increase of etch pit density enlarged of the increase of capacitance. However, abnormal high current density and high electrolyte concentration induced the local dissolution of the foil surface which resulted the decrease of foil capacitance.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1102-1106
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• 2015

A hybrid supercapacitor (HS) is an energy storage device used to enhance the low weight energy density (Wh/kg) of a supercapacitor. On the other hand, a sudden decrease in capacity has been pointed out as a reliability problem after many charge/discharge cycles. The reliability problem of a HS affects the early aging process. In this study, the capacity performance of a HS was observed after charge/discharge. For detailed analysis of the initial charge/discharge cycles, the charge and discharge curve was measured at a low current density. In addition, a solid electrolyte interphase (SEI) layer was confirmed after the charge/discharge. A HC composed of a lithium titanate (LTO) anode and active carbon cathode was used. The charge/discharge efficiency of the first cycle was lower than the late cycles and the charge/discharge rate was also lower. This behavior was induced by SEI layer formation, which consumed Li ions in the LTO lattice. The formation of a SEI layer after the charge/discharge cycles was confirmed using a range of analysis techniques.