• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.161-161
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• 2012

질화티타늄(Titanium Nitride, TiN)은 화학적 안정성이 우수하고, N/Ti 원소 비율에 따라 열전도성 및 전기전도성이 변화하는 특성을 가지고 있어서 Metal Insulator Silicon (MIS) 나 Metal Insulator Metal (MIM) capacitor의 metal electrode 물질로 적용되고 있다. $TiCl_4$와 $NH_3$ gas를 이용하여 $500^{\circ}C$ 이상의 고온 조건에서 Chemical Vapor Deposition (CVD) 법으로 TiN 박막을 증착하는 방식이 가장 널리 사용되고 있으나, TiN 박막 내의 Chlorine (Cl) 원소가 SiO2 두께와 누설전류 밀도를 증가시키는 요인으로 작용하므로 Cl의 거동 및 함량 제어를 통한 전기적인 특성의 향상 평가가 요구되고 있다[1-3]. 본 실험에서는 $SiO_2$ 위에 TiN을 적층 한 구조에서 magnetic sector type의 Secondary Ion Mass Spectrometry (SIMS)를 이용하여 Cl 원소의 검출도 개선 방법을 연구하였다. 일반적인 $Cs^+$ 이온을 이용하여 $Cl^-$ 이온을 검출할 경우에는 TiN 하부에 $SiO_2$가 존재함에 따른 charging effect와 mass interference가 발생되는 문제점이 관찰되었다. 이를 개선하기 위해 Cl과 Cs 원소가 결합된 $ClCs^+$ cluster ion을 검출하는 방법을 시도하였으나, Cl- 이온 검출 방식에 비해 오히려 낮은 검출도를 나타내었으나 Cl 원소가 속하는 halogen 족 원소의 높은 전자 친화도 특성을 이용한 $ClCs_2^+$ cluster ion을 검출하는 방법[4]을 적용한 경우에는 $ClCs^+$ 방식에 비해 검출도가 3order 개선되는 결과를 확보하였으며, 이 결과를 토대로 Cl dose ($atoms/cm^2$) 와 Rs (ohm/sq) 간의 상관 관계에 대해 고찰하고자 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.50-56
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• 2003

It is well known that a partial-discharge(PD) in insulation oil is the source of various physical and chemical phenomena, such as heat, light, gas, chemical transformation, electric current, electromagnetic radiation and ultrasonics. The PD can be detected by measuring one of these changes. Although some techniques are employed in this purpose, several obstacles interfere with an on-line measurement. Ultrasonic-wave detection is a useful method for the diagnosis of the transformer-insulation condition. Conventionally, ulyrasonic waves are detected by Piezo-electric transducer, but we use optical method that has many advantages. In this paper, we constructed a Mach-Zehnder interferometer with optical fiber and investigated the principle of operation. Test arrangement is based on the needle-plane electrode system in oil and applied AC high voltage. Ultrasonic waves were detected and analyzed with wavelet transform.

• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.105-108
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• 2008

In the recent years, increasing interests are being focused on the rational functionalization of the CNTs by some creative methods. However, the considerable toxicity of CNT is still a controversialissue and limits its biological application. To improve the biocompatibility of CNT, in this work we prepared CNT-$TiO_2$ nanocomposites with CNT and organic titanium precursors. Our observations demonstratethat the modified interface could accelerate the heterogeneous electron transfer rates and thusenhance the relevant detection sensitivity, suggesting its potential application as the new strategy for the development of the biocompatible and multi-signal responsive biosensors for the early diagnosis of cancers.

• Polymer(Korea)
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• v.38 no.6
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• pp.809-814
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• 2014

An array structure of conducting polymer microtubule was fabricated for an amperometric biosensor. 3,4-Ethylenedioxythiophene (EDOT) was electropolymerized in the microporous template membrane with poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonic acid) (PEDOT/PSS) composite as a binder. The array structure can provide enhanced current collecting capability due to large active surface area compared to the macroscopic area of the electrode itself. For a biosensor application, the array electrode was tested for $H_2O_2$ detection and showed very sluggish electrochemical response to $H_2O_2$. To enhance the detection efficiency to the oxidation of $H_2O_2$, gold was treated on the electrode by two different approaches: sputtering and electrochemical deposition. Gold treatment with either method greatly enhanced the sensitivity of the electrode to $H_2O_2$. So, conducting polymer microtubule array with gold treatment was expected to be a sensitive amperometric biosensor system based on the detection of $H_2O_2$.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.973-977
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• 2013

These studies were attempted to investigate the change of microbial community of anode of microbial fuel cell using swine wastewater in the enrichment step with the lapse of time. Microbial fuel cells enriched by a 1 : 1 mixture of anaerobic digestive juices of the sewage treatment plant and livestock wastewater. Enrichment culture step was divided into three stages to indentify the microorganisms. It was separated by each lag phase, exponential phase, and stationary phase. These steps were determined by the change of the current value. The current after enrichment was generated about $0.84{\pm}0.06mA$. We were cut out the different 17 bands in the DGGE fingerprint gel to do sequencing. The bands which the concentration was increasing or newly appearing with the lapse of time were included for this study. In the lag and exponential phase, Clostridium, Rhodocyclaceae, Bacteriodetes, and Uncultured bacterium etc. were detected. There were in the stationary phase Geobacter sp., Rhodocyclaceae, Candidatus, Nitrospira, Flavobactriaceae and uncultured bacterium etc. Geobactor among microorganisms detected in this study is known as the Electrochemically active microorganisms. It may include electrochemically active microorganisms to be considered as electrical activity microorganisms.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.190-195
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• 2007

A new electrochemical sensor to selectively determine epinephrine was developed and its analytical characteristics has been investigated. A glassy carbon electrode was modified with Ni(II)-macrocyclic complex which has electrocatalytic effect. It was further modified with physiologically suitable and negatively charged polyuretane benzyl L-glutamate(PUBLG). The present electrode showed long term stability and it could be applied to the selective determination of epinephrine in urine sample with various coexisting compounds. Under the optimum experimental conditions the linear range was $8.0\;{\times}\;10^{-7}\;-\;2.0\;{\times}\;10^{-4}\;M$ and the limit of detection was $1.0\;{\times}\;10^{-7}\;M$. The recovery of epinephrine in urine sample diluted 5 times with buffer solution was $101.5({\pm}3.2)%$ for 6 measurements.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.362-366
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• 2000

$Li_{0.44}MnO_2$cathode material has high reversibility during lithium insertion processes and is not easily damaged through over-charging or over-discharging. $Mn_2O_3$is often present as an impurity phase, and reduce the electrochemical capacity of electrode because this phase is electrochemically inert. Adding of excess NaOH reduced the $Mn_2O_3$to the content under undetectable by X-ray diffraction. Because the capacity can be increased in the cathode materials with larger unit cell, some of the manganese was replaced with titanium having larger ion size, and powders with the formula $Li_{0.44}T_{iy}Mn_{1-y}O_2$(where y = 0.11, 0.22, 0.33, 0.44, and 0.55) was synthesized and characterized. A maximum reversible capacity of 150 mAh/g was obtained for $Li/P(EO)_8$LiTFSI/$Li_{0.44}Ti_{0.22}Mn_{0.78}O_2$cells in electrochemical potential spectroscopy (ECPS) experiments. Cells with the titanium-doped manganese oxides exhibited a fade rate of 0.12 % or less per cycle.

• Analytical Science and Technology
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• v.16 no.3
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• pp.198-205
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• 2003

The ammonium salt of nitrosophenylhydroxylamine, called cupferron, has been used not only as the ligand but also as an oxidizing agent for adsorptive catalytic stripping voltammetry (AdCtSV). Cyclic voltammetry was used for elucidating the electrochemical behavior of Os-cupferron complex in 1 mM phosphate buffer. The optimal conditions for osmium analysis were found to be 1 mM phosphate buffer solution (pH 6.0) containing 0.1 mM cupferron at scan rate of 100 mV/s. By using the plot of reduction peak currents of linear scan voltammograms vs. osmium concentration, the detection limit was $1.0{\times}10^{-7}M$.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.167-167
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• 2000

전지 재료의 충방전 과정 연구에는 X-선 분말회절(x-ray powder diffraction techniques)과 중성자회절을 많이 사용하였다. 하지만 이러한 분석기술은 long-range order의 구조에 관한 정보를 제공하는데 유용하지만 atomic scale의 구조에 관한 정보를 얻기에는 한계가 있다. Li 전지에서의 전기화학적 반응에서는 cathode 물질에 포함된 전이금속의 산화, 환원 반응에 의한 Li 이온의 intercalation (charge process)과 deintercalation (discharge process) 현상이 일어난다. 이러한 충방전 과정은 알려지지 않은 다양한 형태의 위상 변화를 동반하게 되는데 x-선 이나 중성자를 이용한 powder diffraction techniques 로는 단지 정성적인 결정학적 정보를 얻을 수 있다. 따라서 최근에 원자 단위의 local structure에 관한 정보와 electrochemical state에 관한 정보를 동시에 얻을 수 있는 X-ray Absorption Fine Structure (XAFS) 분석기술을 Li 전지분석에 활용하기 시작하였다. XAFS는 하나의 x-ray 흡수원자에 대해서 주변원자들의 원자구조에 관한 정보와 구성 원소의 electrochemical state에 관한 정보를 얻을 수 있는 분석방법이다. X-ray Induced Electron Emission Spectroscopy (XIEES)는 x-ray에 의해서 방출된 전자를 검출하여 스펙트럼을 얻는 기능을 함축적으로 나타낸 것으로, x-ray를 물질 표면에 조사하여 발생하는 광전자, Auger 전자, 이차전자 등을 전자검출기(Channel Electron Multiplier: CEM)로 검출하는 기능과, 시료를 투과한 x-ray와 시료에서 발생하는 형광 x-ray를 비례계수기로 검출하는 기능을 가지고 있다. 이러한 검출 능력을 바탕으로 EXAFS, XANES, Standing Wave Technique, Elemental Composition Analysis, DXRD, Total Reflection Technique 등을 이용하여 물질을 구성하고 있는 원소의 성분, 미세원자구조, 전자구조에 관한 정보를 얻을 수 있는 새로운 spectrometer이다. 본 연구에서는 자체 개발한 XIEES의 XAFS 기능을 이용하여 여러 가지 방법으로 제조한 LiMn2-xO4와 LiMnO2, MnO2에서 Mn K-absorption edge에 대한 chemical state 변화를 측정하였다. Absorption edge에서 chemical shift를 측정하기 위해서는 방사광 가속기 수준의 에너지 분해능(~0.3eV)이 필요하다. 이번 연구에서는 SiO2(3140) monochromator를 사용하고 여기에 맞는 적절한 parameter를 적용하여 x-ray 에너지 분해능을 포항방사광가속기 수준으로 개선하였다. XIEES에서 얻은 스펙트럼과 포항방사광가속기에서 얻은 스펙트럼을 비교하였다. Chemical shift가 일어나는 경향은 두 실험 결과가 잘 일치하였다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1690-1691
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• 2011

본 논문에서는 H1N1 인플루엔자 A 바이러스(influenza A H1N1 virus) 검출을 위한 산화아연 나노구조(zinc oxide nano structure) 기반의 전기화학적 면역센서를 제작하고 그 특성을 분석하였다. H1N1 인플루엔자 A 바이러스는 빠른 전파 속도 때문에 정확하고 빠른 검출이 필요하다. 먼저, 2 $mm^2$의 표면적을 갖는 패턴된 금 전극 위에 열수방식(hydrothermal method)으로 성장시킨 산화아연 나노구조가 선택적으로 형성되도록 리프트-오프(lift-off) 방법을 사용하였다. 0.01 M phosphate buffered saline(pH 7.4)에서 2 ${\mu}g$/mL 농도의 1차 항체를 정전기력에 의해 산화아연 나노구조에 고정화한 후, 10 pg/mL ~ 5ng/mL 농도의 H1N1 항원을 적용하여 포획 항체에 결합시키고 HRP(horseradish peroxidase) 효소가 결합된 검출 항체를 항원에 결합시키는 샌드위치 ELISA법을 이용하였다. HRP와 반응하는 TMB(3,3', 5,5'-tetramethylbenzidine)와 과산화수소가 포함된 acetate buffered 용액(pH 5)을 전해질로 사용하고 순환전압전류 측정법(cyclic voltammetry)으로 센서의 특성을 분석하였다. 측정된 순환전압전류그래프(cyclic voltammogram)에서 H1N1 항원 농도 10 pg/mL ~ 5 ng/mL의 응답 전류는 276.47 ${\pm}$ 21.72 nA (평균 ${\pm}$ 표준편차, n=4) ~ 478.89 ${\pm}$ 6.21 nA로 측정되었고, logarithmic하게 증가하는 응답 전류 특성을 보였다.