• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.329-329
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• 2010

반도체 및 디스플레이의 진공부품은 알루미늄 모제에 전해연마법(electrolytic polishing), 양극산화피막법(Anodizing), 플라즈마 용사법(Plasma spray) 등을 사용하여 $Al_2O_3$ 피막을 성장시켜 사용되고 있다. 반도체 제조공정 중 30~40% 이상의 비중을 차지하는 식각(etching) 및 증착(deposition) 공정은 대부분 플라즈마를 사용하고 있다. 플라즈마에 의해 화학적, 물리적 침식이 발생하여 코팅막에 손상을 일으켜 코팅막이 깨지거나 박리되면서 다량의 Particle을 생성함으로써 생산수율에도 문제를 야기 시킨다고 알려져 있다. 하지만 이들 코팅막을 평가하는 방법은 거의 전무하여 산업계에서 많은 애로를 겪고 있다. 이러한 코팅부품의 내플라즈마 성능평가 방법과 기준이 없어 적절한 교체시기를 파악하기 위한 코팅부품의 손상정도를 정량화 및 평가 방법의 표준화를 구축하는 연구를 수행하였다. 본 연구에서는 이러한 소재의 특성평가를 위해 공정에서 사용 중 손상되어 교체된 샘플의 모폴로지 관찰하고 내전압 측정으로 전기적 특성을 분석하여 손상 전, 후의 변화를 관찰하였다. 또한 플라즈마의 영향에 따른 코팅 막 형태 변화 및 전기적 특성의 변화를 알아보기 위하여 양극산화피막법(Anodizing)으로 $Al_2O_3$를 성장시킨 평가용 샘플을 제작한 후, Plasma chamber 장비를 이용하여 플라즈마 처리에 따른 코팅막의 내전압, 식각율, 표면 미세구조의 변화를 측정하였고 이를 종합적으로 고려하여 진공 장비용 코팅부품의 공정영향에 의한 내플라즈마 특성평가방법 개발에 관하여 연구하였다. 이러한 실험을 통해 플라즈마 처리 후 코팅 막에 크랙이 발생되는 것을 확인할 수 있었고 코팅 막의 손상으로 전기적 특성이 감소를 것을 확인할 수 있었다. 또한 ISPM 장비를 이용하여 진공 장비용 코팅부품이 플라즈마 공정에서 발생하는 오염 입자를 측정할 수 있는 방법을 연구하였다. 이러한 결과를 이용하여 진공공정에서 사용되는 코팅부품이 플라즈마에 의한 손상정도를 정량화 하고 평가방법을 개발하여 부품 양산업체의 진공장비용 코팅부품 개발 신뢰성 향상이 가능할 것으로 본다.

• Journal of Wetlands Research
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• v.24 no.2
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• pp.83-92
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• 2022

The amount of the plastic waste has been increasing according to global demand for plastic. Microplastics are the most hazardous among all plastic pollutants due to their toxicity and unknown physicochemical properties. This study investigates the optimal methodology that can be applied to sewage samples for detecting microplastics before discussing reducing microplastics in MWTPs. In this study, the effect of different pretreatment methods while detecting microplastic analysis of MWTP influent samples was investigated; the samples were collected from the J sewage treatment plant. There are many pretreatment methods but two of them are widely used: Fenton digestion and hydrogen peroxide oxidation. Although there are many pretreatment methods that can be applied to investigate microplastics, the most widely used methods for sewage treatment plant samples are Fenton digestion and H₂O₂ oxidation. For each pretreatment method, there were factors that could cause an error in the measurement. To overcome this, in the case of the Fenton digestion pretreatment, it is recommended to proceed with the analysis by filtration instead of the density separation method. In the case of the H₂O₂ oxidation method, the process of washing with distilled water after the reaction is recommended. As a result of the analysis, the concentration of microplastics was measured to be 2.75ea/L for the sample using the H₂O₂ oxidation method and 3.2ea/L for the sample using the Fenton oxidation method, and most of them were present in the form of fibers. In addition, it is difficult to guarantee the reliability of measurement results from quantitative analysis performed via microscope with eyes. A calibration curve was created for prove the reliability. A total of three calibration curves were drawn, and as a result of analysis of the calibration curves, all R² values were more than 0.9. This ensures high reliability for quantitative analysis. The qualitative analysis could determine the series of microplastics flowing into the MWTP, but could not confirm the chemical composition of each microplastic. This study can be used to confirm the chemical composition of microplastics introduced into MWTP in the future research.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.172-178
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• 2014

In this work, we describe an electrochemical immunosensor for simple, fast and quantitative detection of a urinary hippuric acid (HA). Urinary HA, of molecular weight 180 DA, is one of the major metabolites and biological indicators in toluene-exposed humans. Simple and ubiquitous monitoring of exposure to toluene is very important in occupational health care. We propose the electrochemical immunoassay based on the dopamine-antigen conjugate for detecting hippuric acid. Our electrochemical immunoassay system employs a conjugate of dopamine (DA) as an electrochemical active molecule and hippuric acid (HA) as an antigen. As an electrochemical aspect, dopamine (DA) containing two hydroxyl group can show excellent redox signal. Also, dopamine-tethered hippuric acid (DA-HA) shows the reversible redox signal in the immunoassay. The competition between HA and DA-HA generated electric signals proportional to HA concentration. The electrochemical immunoassay was performed with DA-HA on the screen printed carbon electrodes (SPCEs), and then applies the mixture antigen (HA) and HA-antibody. The electrical signals were proportional to HA in the range of 0.010~2.500 mg/mL which is enough range to be used for the point-of-care.

• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.295-301
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• 1980

The electrical conductivity of solid electrolyte $RbAg_4I_5$ single crystal was studied at various temperatures. The four-probe method was used in measuring the conductance with an ac signal imposed on the specimen. The ionic conductivity was $0.284 ohm^{-1} cm^{-1}\;at\;25^{\circ}C$, and the activation energy for $Ag^+$ ion migration was calulated to be 1.70 kcal/mole. These values agree well with those reported for polycrystalline samples. Reactions at $Ag/RbAg_4I_5$ interface were studied by cyclic voltammetry with a silver reference electrode. It was found that silver ion is reversibly reduced at silver surfaces below zero volt, and iodide was oxidized above +0.67 volt.The anodic current arising from the oxidation of the electrode was small in magnitude initially over a wide range of potential, but, after silver was cathodically deposited on the electrode, reversing the potential sweep to the anodic direction resulted in a sharp peak of anodic current.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.164-171
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• 2014

A highly sensitive and selective non-enzymatic glucose sensor has gained great attention because of simple signal transformation, low-cost, easily handling, and confirming the blood glucose as the representative technology. Until now, glucose sensor has been developed by the immobilization of glucose oxidase (GOx) on the surface of electrodes. However although GOx is quite stable compared with other enzymes, the enzyme-based biosensors are still impacted by various environment factors such as temperature, pH value, humidity, and toxic chemicals. Non-enzymatic sensor for direct detecting glucose is an attractive alternative device to overcome the above drawbacks of enzymatic sensor. Many efforts have been tried for the development of non-enzymatic sensors using various transition metals (Pt, Au, Cu, Ni, etc.), metal alloys (Pt-Pb, Pt-Au, Ni-Pd, etc.), metal oxides, carbon nanotubes and graphene. In this paper, we show that Ni-based nano-particles (NiNPs) exhibit remarkably catalyzing capability for glucose originating from the redox couple of $Ni(OH)_2/NiOOH$ on the surface of ITO electrode in alkaline medium. But, these non-enzymatic sensors are nonselective toward oxidizable species such as ascorbic acid the physiological fluid. So, the anionic polymer was coated on NiNPs electrode preventing the interferences. The oxidation of glucose was highly catalyzed by NiNPs. The catalytically anodic currents were linearly increased in proportion to the glucose concentration over the 0~6.15 mM range at 650 mV versus Ag/AgCl.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.138-144
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• 2010

In order to investigate the electrochemical propertied of titanium electrode for electrolysis, manganese oxide was electrodeposited on surface of mesh titanium by pulse voltammetry. The morphological changes and impedance results of manganese oxide electrodeposited electrode were analyzed by SEM and EDX. The size of electrodeposited manganese oxide on mesh titanium was increased with first cycle pulse time increase, and approximately 100 non-uniform manganese oxide was grown at 10 ms pulse polarization time. Charge transfer resistance($R_{ct}$) of near the overpotential was analyzed by EIS measurement and the feasibility of prepared electrode was evaluated by the overpotential calculated from Tafel plots.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.435-439
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• 2010

Pt-$MoO_3$ electrodes were fabricated on ITO-coated glass by electrodeposition method using 20 mM hydrogen hexachloroplatinate ($H_2PtCl_6$) and 10 mM Mo-peroxo electrolyte. Deposition order was varied, and catalytic activities of synthesized electrodes were compared with that of pure Pt electrode. Scanning Electron Microscopy (SEM) was utilized to examine surface morphology. The crystallinity of synthesized films was analyzed by X-ray Diffraction (XRD), and the oxidation state of both the platinum and molybdenum were determined by X-ray Photoelectron Spectroscopy (XPS) analyses. The catalytic activity and stability for methanol oxidation were measured using cyclic voltammetry (CV) and chronoamperometry (CA) in a mixture of 0.5 M $H_2SO_4$ and 0.5 M $CH_3OH$ aqueous solution. $MoO_3$ electrodeposited on the surface of Pt showed much higher catalytic acitivity and stability than pure Pt electrode due to the good contact between Pt and $MoO_3$.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.138-143
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• 2013

Recently, ZnO nanoparticles have been studied in various application fields due to their physico-chemical properties. In this study, we have researched on the ZnO photocatalytic activity by redox reaction. ZnO nanoparticles have low photocatalytic activity in comparison with $TiO_2$ nanoparticles because it has the disadvantage that the formation of $Zn(OH)_2$ in water solvent. Therefore, we were synthesized ZnO nanoparticles by spray-pyrolysis method, and then studied on stability in water solvent. At the results, the water treated-ZnO nanoparticles showed higher photocatalytic activity than non-treated ZnO nanoparticles because molecular $H_2O$ was increased onto the ZnO surface under the water treatment. Also, we confirmed that the ZnO nanoparticles synthesized by spray-pyrolysis method is very stable in the water solvent.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.613-613
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• 2013

그래핀은 저차원계 구조에서 기인하는 뛰어난 전기적, 물리적, 기계적 성질을 지니고 있어 실리콘 기반 기술을 대체할 전계 효과 트랜지스터 이외에도 투명전극, 초고용량 커패시터, 전계방출 디스플레이 등 다양한 응용분야에 적용 가능하다. 최근에는 이러한 응용 연구분야에서 그래핀과 탄소나노튜브 각각의 단점을 최소화하고 장점을 극대화하기 위한 그래핀-탄소나노튜브 혼성 나노구조에 대한 연구들이 진행되고 있는 추세이다. 이전 연구들에서 환원된 그래핀 산화물(Reduced Graphene Oxide, RGO)을 이용한 그래핀-탄소나노튜브 혼성 나노구조가 제작되었는데, 이는 RGO의 제작과정에서 복잡한 공정과 긴 합성과정이 요구될 뿐 아니라, 복합 물질에서 탄소나노튜브의 밀도 제어가 어렵다는 단점을 지닌다. 또한 현재까지 제작된 그래핀-탄소나노튜브 혼성 나노구조의 경우, 열 화학기상증착법으로 합성된 다층(few-layers)의 그래핀과 탄소나노튜브 혼성 나노구조를 제작하였다 [1-6]. 본 연구에서는 우수한 전기적 특성을 가진 단층(monolayer)의 그래핀을 열 화학기상증착법으로 합성한 후, 그래핀 위에 단일벽 탄소나노튜브를 성장시킴으로써 그래핀-탄소나노튜브 혼성 나노구조를 제작하였다. 합성된 그래핀-탄소나노튜브의 구조적 특징은 주사 전자 현미경과 라만 분광기 측정을 통해 확인하였고, 촉매의 표면 형상 및 화학적 상태는 원자힘 현미경과 X선 광전자 분광법을 통해 확인하였다. 또한 그래핀 기반의 전계 효과 트랜지스터의 경우, 상온에서 그래핀은 우수한 전하 이동도를 가지며 웨이퍼 스케일에서 제작하기 쉬우나 밴드 갭이 없으므로 높은 Ion/Ioff를 가지는 그래핀 기반의 트랜지스터를 만드는 것이 과제이다. 반면 탄소나노튜브는 큰 에너지 갭을 가지고 있으므로 높은 Ion/Ioff를 구현하는 소자 제작이 가능하다. 그리하여 제작된 그래핀-탄소나노튜브 혼성 나노구조의 소자 제작을 통해 전기적 특성을 조사하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.101-101
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• 2011

투명전도성산화물(transparent conducting oxides, TCOs) 박막으로써 널리 쓰이는 산화인듐주석(indium tin oxide, ITO)은 전기 전도성과 광 투과성이 우수하여 주로 유기발광다이오드(organic light-emitting diode, OLED)의 전극, 발광다이오드(light-emitting diode, LED)의 current spreading 층 및 태양전지(solar cell)의 윈도우층(window layer) 등의 광전자 소자로 응용되고 있으나, 고가의 indium 가격과 인체에 유해한 독성 등이 문제점으로 지적되고 있다. 따라서 indium의 함량을 저감한 새로운 조성의 TCO 또는 indium을 함유하지 않은 친환경적인 TCO 대체 재료 개발의 필요성이 증대되고 있다. 이러한 재료 중 하나인 AZO (Al-doped zinc oxide, $Al_2O_3$: 2 wt.%)는 3.82eV의 넓은 에너지 밴드갭을 가지며, 가시광선 및 근 적외선 파장 영역에 대하여 90% 이상의 높은 투과율을 나타낸다. 또한, 습식식각이 가능하며, 매우 풍부하여 원가가 매우 저렴하고, 독성이 없다. 본 연구에서는 박막 증착율이 높고, 제작과정의 조정이 용이한 RF magnetron 스퍼터를 이용하여 glass 기판 위에 AZO 박막을 성장하고, $N_2$ 분위기에서 다양한 온도 조건에서 열처리(rapid thermal annealing, RTA)하여 전기 및 광학적 특성에 대하여 비교 분석하였다. 또한, 이후에 기존의 성장방법과 달리 고가의 진공 장비를 사용하지 않고, 저온에서도 간단한 구조의 장비를 이용하여 균일한 나노구조를 성장시킬 수 있는 전기화학증착법(electrochemical deposition)으로 AZO 박막위에 ZnO 나노로드를 다양한 성장조건에 따라 성장시켜 광학적 특성을 비교 분석하였다.