• 센서학회지
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• 제10권4호
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• pp.259-265
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• 2001

FET형 용존산소 센서는 pH-ISFET를 기본 소자로하여 pH 감지 게이트 근처에 백금으로 된 작업 전극을 형성한 구조를 가지고 있다. 작업전극에 특정한 전위를 인가하면 전기분해로 인하여 용존산소의 농도에 비례하는 수소 이온이 pH 감지 게이트 주변에 발생된다. 따라서 pH-ISFET를 통하여 수소 이온 농도의 변화량을 검출하면 용존산소의 농도를 측정할 수 있게된다. 본 논문에서는 이러한 FET형 용존산소 센서를 어레이 형태로 제작하여 적용하고 측정의 신뢰성을 높이기 위한 알고리즘을 도입한 FET형 용존산소 센서 어레이 측정 시스템을 개발하였다. 또한 상용 용존산소 측정기와 그 성능을 비교 분석하였다.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.23-29
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• 2013

In recent years, development of energy conversion systems using hydrogen as an energy source has been accelerated globally. Even though hydrogen is an environment-friendly energy source, safety and effectiveness issues in storage, transportation, and usage of hydrogen should be clearly resolved in every application. Therefore, sensors for detecting hydrogen leakage, especially for fuel cell electric vehicles, should be designed to have much higher resolution and accuracy in comparison with conventional gas sensors. In this study, we conducted to determine the design parameters for the semiconductor hydrogen sensor with optimized sensing conditions under the thermal distribution characteristic and thermal transfer characteristic. The heat generation study on power supply voltage was studied for correlation analysis of thermal energy according to the power supply voltage variation from 1.0 voltage to 10.0 voltage every 0.5 voltage. And we studied for the temperature coefficient of resistance with hydrogen sensor.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.98-98
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• 2003

비정질 실리콘 박막을 태양전지, 박막 트랜지스터, 이미지 센서, 컬러 디텍터 등에 적용하기 위한 많은 연구가 진행되고 있다. 이중 태양전지에 적용하기 위한 비정질 실리콘 박막은 p/i/n 다이오드 구조를 형성하게 되는데, 태양전지의 효율을 증가시키기 위해 결정질을 형성하거나 실리콘 화합물 박막을 적용한다. 본 연구에서는 비정질 태양전지의 흡수층(absorption layer)으로 사용되는 수소화된 비정질 박막의 결정화에 수소의 희석비가 미치는 영향을 파악하고자 하였다. PECVD 장비로 실란(SiH$_4$)과 수소(H$_2$) 가스를 이용하여 실리콘 박막을 증착하였고, 수소의 희석비(dilution ratio)를 변화시켜 비정질 실리콘 박막 내에 결정질 실리콘이 형성되는 정도를 관찰하였다. SEM과 Raman Spectroscopy를 이용해 박막의 두께 및 결정화도를 측정하였다. 실란에 대한 수소의 희석비가 증가할수록 증착률은 낮아지지만, 결정화도가 높아지는 것을 관찰할 수 있었다. 본 연구에서 형성한 결정질 실리콘 박막을 태양전지의 흡수층에 적용하면 효율 증가에 크게 기여할 것으로 판단된다.

• 센서학회지
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• 제21권6호
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• pp.425-428
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• 2012

This paper presents the fabrication and characterization of graphene based hydrogen sensors. Graphene was synthesized by annealing process of Ni/3C-SiC thin films. Graphene was transferred onto oxidized Si substrates for fabrication of chemiresistive type hydrogen sensors. Au electrode on the graphene shows ohmic contact and the resistance is changed with hydrogen concentration. Nanoparticle catalysts of Pd and Pt were decorated. Response factor and response (recovery) time of hydrogen sensors based on the graphene are improved with catalysts. The response factors of pure graphene, Pt and Pd doped graphenes are 0.28, 0.6 and 1.26, respectively, at 50 ppm hydrogen concentration.

• 센서학회지
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• 제20권3호
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• pp.168-171
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• 2011

Porous 3C-SiC(pSiC) samples with different pore diameters were prepared from poly crystalline N-type 3C-SiC by electrochemical anodization. The pSiC surface was chemically modified by the sputtering of Pd and Pt nano-particles as a hydrogen catalyst. Changes in resistance were monitored with hydrogen concentrations in the range of 110 ppm - 410 ppm. The variations of the electrical resistance in the presence of hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen at room temperature. Regardless of the catalyst, the 25 nm pore diameter samples showed good response and recovery properties. However, the 60 nm samples showed unstable and slow response. It was found that the pore size affects the catalyst reaction and consequently, results in changes of the sensitivity to hydrogen.

• 센서학회지
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• 제19권2호
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• pp.67-86
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• 2010

Hydrogen is emerging as clean fuel and important industrial raw materials. The hydrogen gas is not sensed by the human olfactory system, But the combustion characteristics of hydrogen is that the ignition is very easy, the propagation speed of the flame is very fast and explosion limits is a wide range of 4 %~75 %. Therefore it is extremely in danger, and the need for its leakage detection technologies is especially important in places such as a production, transportation, storage and usage. The hydrogen sensors are classified with ceramic type, semiconductor type, optical type, electrochemical type and so on. Hydrogen sensors and their technologies are reviewed in detail for materials, fabrication process, sensing characteristics, good point and faults, and production and utilization of sensors be discussed.

• 센서학회지
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• 제19권2호
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• pp.87-91
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• 2010

Hydrogen gas sensors were fabricated using $PdO_x$ loaded with SWNTs. The nanoparticle powders of $SWNT_s-PdO_x$ composite were deposited on Si wafer substrates by a vacuum filtering deposition method. The fabricated sensors were tested against hydrogen gas. The composition ratio that exhibited the highest response to hydrogen gases was SWNTs : $PdO_x$ = 98 : 2 in wt% ratio at operating temperature of about $150^{\circ}C$. The response and recovery times were shorter than 1.0 min. in presence of 1000 ppm hydrogen.

• 센서학회지
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• 제18권3호
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• pp.222-225
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• 2009

This paper describes the fabrication and characteristics of Schottky micro hydrogen sensors for high temperatures by using polycrystalline(poly) 3C-SiC thin films grown on Si substrates with thermal oxide layer using APCVD. Pd/poly 3C-SiC Schottky diodes were made and evaluated by I-V and C-V measurements. Electric current density and barrier height voltage were $2{\times}10^{-3}A/cm^2$ and 0.58 eV, respectively. These devices could operate stably at about 400 $^{\circ}$. The characteristics of implemented sensors have been investigated in terms of sensitivity, linearity of response, response rate, and response time. Therefore, from these results, Pd/poly 3C-SiC Schottky devices have very high potential for high temperature $H_2$ sensor applications.

• 한국수소및신에너지학회논문집
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• 제20권5호
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• pp.378-383
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• 2009

Hydrogen is the primary fuel in fuel cell systems. Because of high inflammation and explosion possibility of hydrogen, fuel cell systems require safety measures to prevent hydrogen hazard upon leakage. In this study, a model enclosure was made by referring to a commercial residential fuel cell system and hydrogen leakage experiments and computational simulations were conducted therein. Hydrogen was injected into the cavity through leakage holes located at the bottom while its flow rate was precisely controlled using MFC. The transient sensor signals from hydrogen sensors installed inside the enclosure were recorded and analyzed. The hydrogen sensor signals showed different delay times depending on their position relative to a leakage point, which indicated that hydrogen generally moves upward and accumulates at the upper region of a closed cavity. The inflammable regions with hydrogen concentration over 4% LEL were observed to locate near the leakage hole initially, and broaden towards the upper cavity region afterward. The simulation result showed that detection time at the hydrogen sensor was similar to the pattern of experimental results. However, the maximum concentration of hydrogen had a gap between experiment and simulation at detect point due to measurement errors and reaction rate.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.9-16
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• 2005

We studied the electrochromic properties of hydrated amorphous ruthenium oxide ($RuO_2{\cdot}xH_2O$) thin films using in-situ Raman spectroscopy during electrochemical charging/discharging cycles. We have found that the principal effect of hydrogen insertion into $RuO_2{\cdot}xH_2O$ is reduction of $Ru^{4+}\;to\;Ru^{3+}$, and not formation of new bonds involving hydrogen. We compared the changes in the Raman spectrum of a gasochromic $Pd/RuO_2{\cdot}xH_2O$ film as it is exposed to hydrogen gas with that of electrochemical hydrogen insertion. We tested the changes in the optical transmission of the $Pd/RuO_2{\cdot}xH_2O$ film when exposed to hydrogen gas.