• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.93-98
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• 2010

In this work, the electrochemical properties of surface treated multi-walled carbon nanotubes (MWNTs) were studied. Nitrogen and oxygen functional groups of the MWNTs were introduced by urea and acidic treatment, respectively. The surface functional groups of the MWNTs were confirmed by X-ray photoelectron spectroscopy (XPS) measurements and zeta-potential method. The characteristics of $N_2$ adsorption isotherm at 77 K, specific surface area, and total pore volumes were investigated by BET eqaution, BJH method and t-plot method. Electrochemical properties of the functionalized MWNTs were accumulated by cyclic voltammetry at the scan rates of 50 $mVs^{-1}$ and 100 $mVs^{-1}$ in 1M $H_2SO_4$ as electrolytes. As a result, the functionalized MWNTs led to an increase of capacitance as compared with pristine MWNTs. It was found that the increase of capacitance for urea treated MWNTs was attributed to the increase in density of surface functional groups, resulting in improving the wettability between electrode materials and charge species.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.333-340
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• 1996

The properties of TiN as a barrier against Cu diffusion ere studied by sheet resistance measurement, X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and capacitance-voltage(C-V) measurement. The sensitivities of the various methods were compared. Specimens with Cu/TiN/Ti/SiO2/Si structure were prepared by various deposition techniques and annealed at various temperatures ranging from $500^{\circ}C$ to $800^{\circ}C$ in 10%H2/90%Ar ambient for hours. As the effectiveness of the barrier property of TiN against Cu diffusion was vanished, the irregular-shaped sports were observed and outdiffused Si were detected on the surface of the Cu thin film. The C-V characteristics of the MOS capacitors varied drastically with annealing temperatures. In C-V measurement, the inversion capacitance decreased at annealing temperature range from $500^{\circ}C$ to $700^{\circ}C$ and increased remarkably at $800^{\circ}C$. These variations may be due to the Cu diffusion through TiN into $SiO_2$ and Si.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.59-65
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• 2001

Epoxy/$BaTiO_3$composite capacitor films with excellent stability at room temperature, uniform thickness, and electrical properties over a large area ware successfully fabricated. The composite capacitor films with good film formation capability and easy process ability were made from epoxy resin developed for ACF as a matrix and two kinds of $BaTiO_3$powders as fillers to increase the dielectric constant of the composite film. The crystal structure of the powders and its effects on dielectric constant of the films were investigated by X-ray diffraction (XRD). And the optimum amount of dispersant, phosphate ester, was determined by viscosity measurement of suspension. DSC and dielectric property tests were conducted to decide the right curing temperature and the optimum amount of the curing agent. As a result, the capacitors of 7 $\mu \textrm{m}$ thick film with 10 nF/$\textrm{cm}^2$ and low leakage current were successfully demonstrated.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.94-98
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• 2005

$RuO_2$ is widely studied as a lower electrode material for high dielectric capacitors in DRAM (Dynamic Random Access Memories) and FRAM (Ferroelectric Random Access Memories). In this study, the effects of hydrogen, oxygen, and argon Electron Cyclotron Resonance (ECR) plasma pretreatments on deposited by Metal Organic Chemical Vapor Deposition (MOCVD) $RuO_2$ nucleation was investigated using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) analyses. Argon ECR plasma pretreatment was found to offer the highest $RuO_2$ nucleation density among these three pretreatments. The mechanism through which $RuO_2$ nucleation is enhanced by ECR plasma pretreatment may be that the argon or the hydrogen ECR plasma removes nitrogen and oxygen atoms at the TiN film surface so that the underlying TiN film surface is changed to Ti-rich TiN.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.495-501
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• 2020

The various sintered samples comprising of 72 wt% (Al₂O₃) : 28 wt% (SiO₂) based ceramics were fabricated using a colloidal processing route. The phase analysis of the ceramics was performed using an X-ray diffractometer (XRD) at room temperature confirming the presence of Al₂O₅Si and Al_5.33Si_0.67O_9.33. The surface morphology of the fracture surface of the different sintered samples having different sizes of grain distribution. The resistive and capacitive properties of the three different sintered samples at frequency sweep (1 kHz to 1 MHz). The contribution of grain and the non-Debye relaxation process is seen for various sintered samples in the Nyquist plot. The ferroelectric loop of the various sintered sample shows a slim shape giving rise to low remnant polarization. The excitation performance of the sample at a constant electric signal has been examined utilizing a designed electrical circuit. The above result suggests that the prepared lead-free ceramic can act as a base for designing of dielectric capacitors or resonators.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.567-567
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• 2012

Since the carbon nanotubes (CNTs) have extraordinary material properties, many researchers are trying to make a practical application in various fields [1]. In particular, the high surface area of CNTs was fascinated for nano-template on the catalytic system. $RuO_2$ coated CNTs are useful functional nano-composites in many applications, including super capacitors, fuel cells, biosensors, and field emitters. However, the research of interaction between CNTs and $RuO_2$ was not satisfied with various fields [2]. In this study, we will introduce the change of chemical and electrical state of $RuO_2$/CNTs at different temperatures by synchrotron radiation photoemission spectroscopy (SRPES). The t-MWCNTs used in this experiment were grown on the Ni/TiN/Si substrates by chemical vapor deposition. $RuO_2$ of 4-20 nm in thickness was deposited on the t-MWNTs by sputter. The SRPES measurements were carried out at the 4B1 beamline of the Pohang Accelerator Laboratory in Korea. The result of XPS measurement indicates that the deposited $RuO_2$ on the CNTs was reduced into pure Ru at above $300^{\circ}C$. And we confirmed that the effective work function of $RuO_2$/CNTs was decreased with increasing temperature.

• Journal of Environmental Health Sciences
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• v.26 no.2
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• pp.97-107
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• 2000

PCBs [Polychlorinated biphenyls] are halogenated aromatic compounds with the empirical formula C12H10-nCln(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors, transformers, plasticizers, lubricant inks, and paint additives. once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their high degree of lipophilicity. In 1970s, the worldwide production of PCBs seem to be still in use. The environmental load of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seem to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs I the serum samples of 112 women by GC/MSD(Hewlett Packard 5897 Gas Chromatography-Mass Chromatography Detector) and CG/ECD(Hewlett Packard 5890 series-II gas chromatography-Electron capture detector, U.S.A). The main results of this study were as follows; The mean and standard deviation of serum PCBs were 3.613, 0.759 ppb, respectively and median of it was 3.828 ppb. The correlation coefficients of the concentrations of 13 PCB congeners ranged from 0.7913 to 0..9985 and were significantly correlated between each items(p=0.0001). The PCB concentrations were positively associated with age(simple linear regression; R2=0.86, =0.08023, p<0.001) and with total lipids in serums(simple linear regression; R=0.7058, =0.00486, p<0.001). The age adjusted model (Y=$\beta$0+$\beta$1age+$\beta$2X) was applied for possible predictors of PCBs levels in serum. For BMI(Body Mass Index), major residential area, and fish, meat, and dairy consumption, there was no association with PCBs levels, Also there was negative association for the number of pregnancy and lactation period with PCBs levels.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.759-766
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• 1994

Our investigation aimed to reduce the leakage current of $Ta_2O_5$ thin film capacitor by layering SnOz thin film layer under Ta thin film, thereby supplying extra oxygen ions from the $SnO_{2}$ underlayer to enhance the stoichiometry of $Ta_2O_5$ during the oxidation of Ta thin film. Tantalum was evaporated by e-beam or sputtered on p-Si wafers with various deposition temperatures and was oxidized by dry--oxygen at the temperatures between $500^{\circ}C$ and $900^{\circ}C$. Aluminum top and bottom electrodes were formed to make Al/$Ta_2O_5$/p-Si/Al or $Al/Ta_2O_5/SnO_2$p-Si/AI MIS type capacitors. LCR meter and pico-ammeter were used to measure the dielectric constants and leakage currents of the prepared thm film capacitors. XRD, AES and ESCA were employed to confirm the crystallization of the thin f~lm and the compositions of the films. Dielectric constant of $Ta_2O_5$ thin film capacitor with $SnO_{2}$ underlayer was found to be about 200, which is about 10 times higher than that of $Ta_2O_5$ thin film capacitor without $SnO_{2}$ underlayer. In addition, higher oxidation temperatures increased the dielectric constants and reduced the leakage current. Higher deposition temperature generally gave lower leakage current. $Ta_2O_5/SnO_2$ capacitor deposited at $200^{\circ}C$ and oxidized at $800^{\circ}C$ showed significantly lower leakage current, $10^{-7}A/\textrm{cm}^2$ at $4 \times 10^{5}$V/cm, compared to the one without $SnO_{2}$ underlayer. XRD showed that $Ta_2O_5$ thin film was crystallized above $700^{\circ}C$. AES and ESCA showed that initially the $SnO_{2}$, underlayer supplied oxygen ions to oxidize the Ta layer, however, Sn also diffused into the Ta thin film layer to form a new $Ta_xSn_YO_Z$ , ternary oxide layer after all.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.

• Journal of Environmental Health Sciences
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• v.27 no.2
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• pp.127-137
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• 2001

Polychlorinated biphenyls(PCBs) are halogenated aromatic compounds with the empirical formula $C_{12}$ $H_{10-n}$C $l_{n}$(n=1~10), and are a mixture of possible 209 different chlorinated congeners. PCBs were widely used as dielectric fluids for capacitors and transformers, plasticizers, lubricant inks and paint addirives. Once released into the environment, PCBs persist for years because they are so resistant to degradation. In addition to their persistence in the environment, PCBs in ecological food chains undergo biomagnification because of their high degree of lipophilicity. In 1970s, the worldwide production of PCBs was ceased and the import of PCBs was prohibited since 1983 in Korea. In spite of these actions, many PCBs seems to be still in use. The environmental load of PCBs will continue to be recycled through air, land, water, and the biosphere for decades to come. This study was conducted to measure the concentrations of PCBs in the serum samples of 112 women by GC/MSD and GC/ECD. The main results of this study were as follows. 1. PCBs were detected in all samples. The mean $\pm$SD levels of PCBs in the serum were 3.613$\pm$0.759 ppb, and median were 3.828 ppb. 2. The correlation coefficients of the concentrations of 13 PCB congeners were from minimum, 0.7913 to maximum, 0.9985, and all was significant(p=0.0001). The correlation coefficient between the concentrations of PCBs and p,p'-DDE was 0.9641(p=0.0001). 3. There was a positive association between age and PCBs' concentrations (simple linear regression ; $R^2$=0.86, $\beta$=0.08023, p<0.001). 4. There was a positive association between total lipids in the serum and PCBs' concentrations (simple linear regression ; $R^2$=0.7058, $\beta$=0.00486, p<0.001). 5. For possible predictors of PCBs and p,p' -DDE levels in the serum, age adjusted model (Y=$\beta$$_{0}$+$\beta$$_1$age+ $B_2$X) was applied. For BMI, major residential area, wether to eat caught fish by angling, where to eat caught fish by angling(by parents in the past), fish consumption, meat consumption, meat consumption, and dairy consumption, there was no association. For total conception frequency and lactation frequency and lactation period, there was negative association.ion.