• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.9
• /
• pp.732-736
• /
• 2009

Protons are irradiated into SOl wafers under total dose of 100 krad, 500 krad, 1 Mrad and 2 Mrad to analyze the irradiation effect. The electrical properties are analyzed by pseudo MOSFET technology after proton irradiation. The wafers are annealed to stabilize generated defects in a nitrogen atmosphere at $300^{\circ}C$ for 1 hour because proton irradiation induces a lot of unstable defects in the surface silicon film. Both negative and positive turn-on voltages are shifted to negative direction after the irradiation. The more proton total dose, the more turn on voltage shifts. It means that positive oxide trap charge is generated in the buried oxide(BOX). The minority carrier lifetime which is analyzed by the drain current transient characteristics decreases with the increase of proton total dose. The proton irradiation makes crystal defects in the silicon film, and consequently, the crystal defects reduce the carrier lifetime and mobility. As these results, it can be concluded that pseudo MOSFET is a useful technology for the analysis of irradiated SOI wafer.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.9
• /
• pp.1303-1307
• /
• 2003

The low molecular water-soluble chitosan nanoparticles (LMWSC-NPs) were prepared, which was modified with hydrophilic and hydrophobic moieties to evaluate the potential for pharmaceutics application. The synthesis of LMWSC-NPs was identified by FT-IR and $^1H$-NMR spectra. Also, we measured the photon correlation spectroscopy (PCS), transmission electron microscope (TEM) and atomic force microscope (AFM) to investigate the characteristics and morphology of the LMWSC-NPs. At the PCS measurement, the more increase the number of substitutive group, the more decrease the positive charge of LMWSC-NP surface. From the results of TEM and AFM, spherical morphologies were observed, and their sizes were 30-150 nm. Resultantly, LMWSC-NPs prepared in this experiment will be expected as a suitable device for the drug targeting system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.279-282
• /
• 2001

The IBE(ion beam etching)-induced Schottky barrier variation which depends on various etching history related with ion energy, incident angle and etching time has been investigated using voltage-current, capacitance-voltage characteristics of metal-etched silicon contact and morphology of etched surface were studied using AFM(atomic force microscope). For ion beam etched n-type silicons, Schottky barrier is reduced according to ion beam energy. It can be seen that amount of donor-like positive charge created in the damaged layer is proportional to the ion energy. By contrary, for ion beam etched p-type silicons, the Schottky barrier and specific contact resistance are both increased. Not only etching time but also incident angle of ion beam has an effect on barrier height. Taping-mode AFM analysis shows increased roughness RMS(Root-Mean-Square) and depth distribution due to ion bombardment. Annealing in an N$_2$ ambient for 30 min was found to be effective in improving the diode characteristics of the etched samples and minimum annealing temperatures to recover IBE-induced barrier variation were related to ion beam energy.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.11
• /
• pp.1699-1705
• /
• 1989

Nitridation of about 300\ulcornerSiO2 filmss thermally grown on Si was performed in NH3 plasm ambient (0.2-2 torr) at 900\ulcornerC-1100\ulcorner for 15-20 minutes. The peoperties of those films have been investigated by analyzing the AES and the SIMS data, and the results of the I-V and the C-V measurements. At the plasma ambient of less than 1.5 torr pressure, etching of the films have been shown. Above the 1.5 torr pressure, however, SiO2 films were nitrided as SiIxNy. Plasma thermal nitridation of SiO2 by addition of small amount (6%) of CF4 to the NH3 showed higher pile-up N concentration in the surface region of SiOxNy film. The higher the nitridation temperature is and the longer the nitridation time is the larger the dielectric constant is. The plasma thermal nitridation of silicon dioxide on silicon causes the flat-band voltage shift based on the formation of the positive charge. The conduction mechanism for SiOxNy films could be elucidated by Fowler-Nordheim tnneling model. By SIMS analysis, surface of the film nitrided in plasma process has less contamination than that of the film nitrided in open-tube process.

• Journal of the Semiconductor & Display Technology
• /
• v.12 no.3
• /
• pp.41-46
• /
• 2013

Efficient and inexpensive solar cells are necessary for photo-voltaic to be widely adopted for mainstream electricity generation. For this to occur, the recombination losses of charge carriers (i.e. electrons or holes) must be minimized using a surface passivation technique suitable for manufacturing. Recently it has been shown that aluminum oxide thin films are negatively charged dielectrics that provide excellent surface passivation of silicon solar cells to attract positive-charged holes. Especially aluminum oxide thin film is a quite suitable passivation on the rear side of p-type silicon solar cells. This paper, it demonstrate the interfacial microstructure and electrical properties of mono-crystalline silicon surface passivated by $Al_2O_3$ films during firing process as applied for screen-printed solar cells. The first task is a comparison of the interfacial microstructure and chemical bonds of PECVD $Al_2O_3$ and of PEALD $Al_2O_3$ films for the surface passivation of silicon. The second is to study electrical properties of double-stacked layers of PEALD $Al_2O_3$/PECVD SiN films after firing process in the temperature range of $650{\sim}950^{\circ}C$.

• Membrane Journal
• /
• v.32 no.1
• /
• pp.23-32
• /
• 2022

Bacteria grow biofilm on various surface such as separation membrane, food packaging film and biomedical device. Growth of biofilm is associated with the formation of a complex structure of exopolysaccharides. Effect of antibacterial effect reduce drastically once the biofilm developed due to the difficulties in mass transport of antimicrobial agent. In order to enhance the antibacterial activity, surface of the membrane is modified, coated or immobilized with functional materials with biocidal properties. One of the idea is to introduce positive charge on the membrane surface by the presence of quaternary ammonium group which might displace divalent metal ion such as magnesium or calcium present in the bacteria cell wall. Efficacy of cell membrane disruption depends on the mobility of the agents available directly on the surface environment. In this review, various biocidal agents like quaternary ammonium group, helamine or zwitter ion containing membrane are discussed.

• Journal of Energy Engineering
• /
• v.23 no.3
• /
• pp.150-156
• /
• 2014

In this study, we implemented a research for improving performance of redox flow battery (RFB) via enhancing reaction rate of vanadium reaction ($[VO]^{2+}/[VO_2]^+$) that was a rate determining step. For doing that, porous catalyst, CMK3 was employed and its perfoamance was compared with that of Vulcan(XC-72) and commercial Pt/C (Johnson-Matthey Pt 20wt.%). Cyclic voltammetry (CV) was used for inspecting reactivity, while its structural feature was measured by TEM and BET&BJH. Also, Charge-discharge trend was evaluated by single cell tests. As result, CMK3 showed 6 times better catalytic activity and twice better reversibility than Vulcan(XC-72), while it showed larger surface area than Vulcan XR due to its porous structure. Furthermore, CMK3 indicated 85% of reactivity and reversibility of commercial Pt/C despite its Pt-less situation. In single cell tests, when RFB adopted CMK3 as catalyst for positive electrode, its charge-discharge curve result was better than that adopted commercial Pt/C.

• Korean Journal of Soil Science and Fertilizer
• /
• v.16 no.4
• /
• pp.318-324
• /
• 1983

Electrochemical properties of Georgia kaolinite in aqueous suspension were studied by ion adsorption, potentiometric titration, and electrophoretic mobility measurements. Kaolinite in 0.001 M and 0.1 M NaCl solution showed qualitatively both pH independent and pH depender negative and positive charges through pH range 2.5-11.0 when dissolved aluminum ions from kaolinite were considered as well as $Na^+$ and $Cl^-$ as index ions. Electrophoretic mobilities (EM) of 0.02 wt. % kaolinite suspension in distilled water and 0.001 M NaCl solution were approximately constant against mobility measuring time consumed in the electrophoresis cell at different pH values, and isoelectric points(IEP) were around pH 4.7. EM values in 0.1 M NaCl solution were positive and constant against mobility measuring time below pH 4; but above pH 4, EM values were negative for the first 10 seconds followed by positive values which became approximately constant through stepped changes after 10 minutes. Hydrated cations may bind to the six- member oxygen ring sites having multiple partial negative charges on the exterior tetrahedral layer surface by both electrostatic and hydrogen bonding force while hydrated anions bind to the partially positively charged hydrogen atoms on the exterior octahedral layer surface. Parts of the aluminol groups on the exterior octahedral layer surface as well as edge faces may be involved in complex reactions and have both anion and cation exchange capacities in the electrolyte solution above pH 4.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.938-946
• /
• 2008

This study is on sealing leakage holes where are in landfills to make clay cakes with clay particles, which have a negative surface charge using the method of electrophoresis. Generally, electrophoresis is the motion of charged particles in a colloid under the influence of an electric field; particles with a positive charge go to the cathode and negative to the anode. In this study in order to develop the prevention system of leakages of the leachate in landfills, one-dimensional electrophoresis tests were conducted for determining the properties of the motion of the electrophoresis and cutoff using the method of electrophoresis depending on various the effect factors such as types of clays, concentrations of the clays, and applied electric field. In case of the experiments of determining the optimum clays, Na and Ca-Bentonite, Na and Ca-Montmorillonite, which have greater zeta-potential, cation, exchange capacity as well as ability of cutoff, and Micro-cement inducing cementation were chosen and then the effect of those clays was investigated. Moreover, the properties of the motion and settling of the clays were investigated following electric field varied from 0 to 1V/cm at different concentration of the clays in order to determine both the properties of the motion of the clays and the efficiency of electric field when applying different direct current. Ultimately, the ability of cutoff was examined through measuring the permeability of the clay cakes derived from the one-dimensional electrophoresis tests.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.2
• /
• pp.242-247
• /
• 1987

Electrophysical phenomena at the silicon semiconductor-electrolyte solution interfaces were analyzed based on the zeta potential of the electrical double layer and microelectrophoresis. The suspensions were composed of the p or n-type silicon particles suspended in the KCI or pH buffer solutions. The approximate diameter of the prepared and sampled sioicon semiconductor pardticles was 1.5\ulcorner. The sign of the zeta poetntials of the p and n-type silicon particles in the KCl and pH buffer solution was positive. A range of electrophoretic mobilities of the p and n-type silicons in the KCl solutions was 5.5-8.9x10**-4 cm\ulcornerV-sec and 4.2-7.9x10**-4cm\ulcornerV-sec, respectively. The range of zeta potentials corresponding to the electrophoretic mobilities is 70.4-114.0mV nad 53.9-101.2mV, respectively. On the other hand, a range of electrophoretic mobilities of the p and n-type silicons in the pH buffer solutions was 1.1x10**-4-2.2x10**-3cm\ulcornerV-sec and 0-2.1x10**-3cm\ulcornerV-sec, respectively. The range of zeta potentials corresponding to the electrophoretic mobilities is 14.1-281.6mV and 0-268.8mV, respectively. The zeta potentials and electrical double layers of the doped silicon semiconductors are decisively influenced by the positively charged ions in the solutions. The maximum values of the zeta potentials in the KCl solutions appeared at a concentration of about 10-\ulcorner. The isoelectric point of the n-type silicon semiconductors appeared at about a pH 7. The effect of the space charge of the doped silicon semiconductors can be neglected compare with the effect of the surface charge.