• 한국결정성장학회지
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• 제10권2호
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• pp.105-110
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• 2000

APCVD(Atrmos phere Pressure Vapor Deposition)법으로 $\alpha$-$Fa_{2}O_{3}/SnO_{2}$계 박막 가스센서 소자를 제조하여 열처리(Heat treatment)하였으며, 가연성 가스($CH_4$, $H_2$, LPG)에 대하여 감지 특성(Sensitivity)을 측정하였다. 감지특성 향상을 위해 소자를 $400^{\circ}C$, $450^{\circ}C$, $500^{\circ}C$, $550^{\circ}C$, $600^{\circ}C$에서 각각 2시간동안 열처리하였으며 $500^{\circ}C$에서 2시간 동안 열처리하였을 때 가장 우수한 감응도를 조사하였다. 특히 $H_2$에 대하여 가장 민감한 반응을 보였다. 최적의 작동온도를 찾기 위해 $100^{\circ}C$~$300^{\circ}C$으로 변화하며 가스 감응도를 조사하였다. 제작된 소자는 작동온도 $175^{\circ}C$, 측정 범위 500ppm ~ 10,000ppm에서 $H_2$일 경우 감지도가 62%~76%를 가졌으며, $CH_2$의 경우 16%~58%, LPG의 경우 8%~37%이였다. 또한 열처리한 것과 안한 것의 감응도의 차이는 약 10%이었다. LPG 1,000ppm에서의 장기안정성은 감응도 30%의 값으로 수렴하였다.

• 한국재료학회지
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• 제20권12호
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• pp.636-639
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• 2010

ZnO thin films were prepared on a glass substrate by radio frequency (RF) magnetron sputtering without intentional substrate heating and then surfaces of the ZnO films were irradiated with intense electrons in vacuum condition to investigate the effect of electron bombardment on crystallization, surface roughness, morphology and hydrogen gas sensitivity. In XRD pattern, as deposited ZnO films show a higher ZnO (002) peak intensity. However, the peak intensity for ZnO (002) is decreased with increase of electron bombarding energy. Atomic force microscope images show that surface morphology is also dependent on electron bombarding energy. The surface roughness increases due to intense electron bombardment as high as 2.7 nm. The observed optical transmittance means that the films irradiated with intense electron beams at 900 eV show lower transmittance than the others due to their rough surfaces. In addition, ZnO films irradiated by the electron beam at 900 eV show higher hydrogen gas sensitivity than the films that were electron beam irradiated at 450 eV. From XRD pattern and atomic force microscope observations, it is supposed that intense electron bombardment promotes a rough surface due to the intense bombardments and increased gas sensitivity of ZnO films for hydrogen gas. These results suggest that ZnO films irradiated with intense electron beams are promising for practical high performance hydrogen gas sensors.

• 한국세라믹학회지
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• 제39권9호
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• pp.840-845
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• 2002

오존 가스센서는 저가이고 휴대 및 사용이 간편하며 감도가 높고 우수한 선택성을 지닌 반도체식 가스센서가 대안으로 부각되고 있다. 본 연구에서는 R.F. magnetron sputtering법을 이용하여 ITO($In_2O_3 95%,\;SnO_2$ 5%) 박막을 알루미나 기판위에 증착시켰다. 증착시 기판온도는 300$^{\circ}C$와 500$^{\circ}C$였고, 시편의 일부를 공기중 500$^{\circ}C$에서 4시간 동안 열처리하였다. ITO 가스 감지막은 열처리 전${\cdot}$후 모두 결정을 형성하였다. 오존 가스에 대한 감도측정 결과, 300$^{\circ}C$에서 증착한 다음 열처리한 센서에서 가장 높은 감도(1 ppm이하 감지 가능)를 나타내었다. 작동온도가 높을수록 감도는 줄어들었지만 빠른 응답 특성과 안정성을 가졌다.

• 센서학회지
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• 제30권5호
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• pp.331-336
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• 2021

The Non-dispersive Infrared (NDIR) gas sensor has high selectivity, measurement reliability, and long lifespan. Thus, even though the NDIR gas sensor is expensive, it is still widely used for carbon dioxide (CO₂) detection. In this study, to reduce the cost of the NDIR CO₂ gas sensor, we proposed the new optical waveguide structure design based on ready-made gas pipes that can improve the sensitivity by increasing the initial light intensity. The new optical waveguide design is a structure in which a part of the optical waveguide filter is inclined to increase the transmittance of the filter, and a parabolic mirror is installed at the rear end of the filter to focus the infrared rays passing through the filter to the detector. In order to examine the output characteristics of the new optical waveguide structure design, optical simulation was performed for two types of IR-source. As a result, the new optical waveguide structure can improve the sensitivity of the NDIR CO₂ gas sensor by making the infrared rays perpendicular to the filter, increasing the filter transmittance.

• 한국재료학회지
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• 제20권8호
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• pp.408-411
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• 2010

Indium doped $SnO_2$ thick films for gas sensors were fabricated by a screen printing method on alumina substrates. The effects of indium concentration on the structural and morphological properties of the $SnO_2$ were investigated by X-ray diffraction and Scanning Electron Microscope. The structural properties of the $SnO_2$:In by X-ray diffraction showed a (110) dominant $SnO_2$ peak. The size of $SnO_2$ particles ranged from 0.05 to $0.1\;{\mu}m$, and $SnO_2$ particles were found to contain many pores, according to the SEM analysis. The thickness of the indium-doped $SnO_2$ thick films for gas sensors was about $20\;{\mu}m$, as confirmed by cross sectional SEM image. Sensitivity of the $SnO_2$:In gas sensor to 2000 ppm of $CO_2$ gas and 50 ppm of H2S gas was investigated for various indium concentrations. The highest sensitivity to $CO_2$ gas and H2S gas of the indium-doped $SnO_2$ thick films was observed at the 8 wt% and 4 wt% indium concentration, respectively. The good sensing performances of indium-doped $SnO_2$ gas sensors to $CO_2$ gas were attributed to the increase of oxygen vacancies and surface area in the $SnO_2$:In. The $SnO_2$:In gas sensors showed good selectivity to $CO_2$ gas.

• 열처리공학회지
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• 제24권2호
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• pp.87-91
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• 2011

Single layer Sn doped $In_2O_3$ (ITO) films and ITO 50 nm / Au 10 nm / ITO 40 nm (IAI) multilayer films were prepared with electron beam assisted magnetron sputtering on glass substrates. The effects of the Au interlayer, post-deposition atmosphere annealing and intense electron irradiation on the methanol gas sensitivity were investigated at room temperature. As deposited ITO films did not show any diffraction peaks in the XRD pattern, while the IAI films showed the diffraction peak for $In_2O_3$ (400). In this study, the gas sensitivity of ITO and IAI films increased proportionally with the methanol vapor concentration and an intense electron beam irradiated IAI film shows the higher sensitivity than the others film. From the XRD pattern, it is supposed that increased crystallization promotes the gas sensitivity. This approach is promising in gaining improvement in the performance of IAI gas sensors used for the detection of methanol vapor at room temperature.

• Carbon letters
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• 제12권3호
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• pp.162-166
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• 2011

Conducting polymer-coated multiwalled carbon nanotubes (MWCNTs) were prepared by template polymerization in order to enhance their gas sensitivity. This investigation of the conducting polymer phases that formed on the surface of the MWCNTs is based on field-emission scanning electron microscopy images. The thermal stability of the conducting polymer-coated MWCNTs was significantly improved by the high thermal stability of MWCNTs. The synergistic effects of the conducting polymer-coated MWCNTs improve the gas-sensing properties. MWCNTs coated with polyaniline uniformly show outstanding improvement in gas sensitivity to $NH_3$ due to the synergistic combination of efficient adsorption of $NH_3$ gas and variation in the conduction of electrons.

• 한국진공학회지
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• 제16권2호
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• pp.91-98
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• 2007

한국표준과학연구원 진공기술센터에서 잔류기체분석기 교정장치를 개발하였으며, 이 장치를 이용하여 서로 다른 구조를 가진 두개의 사중극 질량분석기 (quadrupole mass spectrometer)의 질소, 아르곤, 헬륨에 대한 기체감도를 측정하였다. 그 결과 기체감도는 QMS 구조와 상관없이 기체의 질량이 클수록 높게 나타났고 압력에 따라서도 다른 특성을 보였으므로 정확한 사용을 위해서는 기체감도를 꼭 보정해야 함을 알 수 있었다.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.83-88
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• 1996

Long term stability, sensitization in air, and gas sensing behaviors of tin oxide films were investigated with doping of antimony and palladium. The tin oxide films were prepared on a Corning glass by reactive rf sputtering method and tested for detection of hydrogen gas. Sb-doping improved a long-term stability in the base resistance of $SnO_2$ film sensor. A small amount of Pd doping caused the optimum sensor operating temperature to reduce and also enhanced the gas sensitivity, compared with the undoped $SnO_2$ film. Gas sensitivity depended largely on the film thickness. The important sensitization reactions for sensor operating were $(O_{2ads})+e^-\;{\rightarrow}\;2(O_{ads})^-$ on the surface of $SnO_2$ film at elevated temperature in air and a followed reaction of hydrogen atoms with $(O_{ads})^-$ ions.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.16.1-16.1
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• 2011

Gas sensor properties of $WO_3$ nanowire structures have been studied. The sensing layer was prepared by deposition of tungsten metal on porous single wall carbon nanotubes followed by thermal oxidation. The morphology and crystalline quality of $WO_3$ material was investigated by SEM, TEM, XRD and Raman analysis. A highly porous $WO_3$ nanowire structure with a mean diameter of 82 nm was obtained. Response to CO, $NH_3$ and $H_2$ gases diluted in air were investigated in the temperature range of $100{\sim}340^{\circ}C$ The sensor exhibited low response to CO gas and quite high response to $NH_3$ and $H_2$ gases. The highest sensitivity was observed at $250^{\circ}C$ for $NH_3$ and $300^{\circ}C$ for $H_2$. The effect of the diameters of $WO_3$ nanowires on the sensor performance was also studied. The $WO_3$ nanowires sensor with diameter of 40 nm showed quite high sensitivity, fast response and recovery times to $H_2$ diluted in dry air. The sensitivity as a function of detecting gas concentrations and gas sensing mechanism was discussed. The effect of dilution carrier gases, dry air and nitrogen, was examined.