• Journal of the Korean Physical Society
• /
• 제73권12호
• /
• pp.1867-1872
• /
• 2018

This study proposes a route for surface modification for p-type cobalt oxide-based gas sensors. We deposit a thin layer of Ni on the Co oxide film by sputtering process and annealed at $350^{\circ}C$ for 15 min in air, which changes a typical sputtered film surface into one interlaced with a high density of hemispherical nanoparticles. Our in-depth materials characterization using transmission electron microscopy discloses that the microstructure evolution is the result of an extensive inter-diffusion of Co and Ni, and that the nanoparticles are nickel oxide dissolving some Co. Sensor performance measurement unfolds that the surface modification results in a significant sensitivity enhancement, nearly 200% increase for toluene (at $250^{\circ}C$) and CO (at $200^{\circ}C$) gases in comparison with the undoped samples.

• 한국정보통신학회논문지
• /
• 제10권9호
• /
• pp.1641-1647
• /
• 2006

나노입자 크기를 가진 얇은 $SnO_2$ 박막을 이용하여 CO 및 $H_2S$에 대한 우수한 감도를 가지는 복합 마이크로 가스센서 어레이를 제작하였다. 나노입자의 박막을 만들기 위해서 약 $2500{\AA}$ 두께의 $SnO_2,\;SnO_2(+Pt),\;SnO_2(+CuO)$ 막을 셰도우마스크를 사용하여 형성 한 후, 이를 $600{\sim}800^{\circ}C$의 온도에서 산화하므로서 나노입자의 $SnO_2$ 모물질의 가스감지 박막을 형성하였다. 실리콘 기판의 마이크로센서의 형태로 제작된 $SnO_2(Pt)$ 및 $SnO_2(+CuO)$ 가스센서는 각각 CO 및 $H_2S$ 가스에 대한 매우 우수한 감도를 나타내는 것을 확인하였다.

• 한국전기전자재료학회논문지
• /
• 제11권11호
• /
• pp.1001-1006
• /
• 1998

$WO_3$ based semiconduction sensor have been reported to have excellent sension properties to $NO_x$ gases by many researchers. In this study appropriate $WO_3$ precursor have been chosen and thin film sensors were fabricated by metallo organic deposition process. Their sensing characteristics were investigated as a function of NO concentration, heat treatment, and measuring temperature. Tungsten dichloro triethoxide was found to be a good precursor for $WO_3$ thin film in this method. Samples heat treated at $600^{\circ}C$ showed sensitivity (S) 200 to 50 ppm NO gas when measuring temperature was $150^{\circ}C$.

• 수산해양기술연구
• /
• 제29권4호
• /
• pp.272-278
• /
• 1993

The trimethylamine-sensing characteristics of ZnO based thin film semiconductors and the sensitivity enhancement by squttering conditions have been investigated to develop a new type sensor for detecting fish freshness. The sensor fabricated with a 300nm of ZnO thin film with 4 wt% Al sub(2) O sub(3) and 1 wt% TiO sub(2) exhibited the highest sensitivity of 155 at 30$0^{\circ}C$ of working temperature and to the 240 ppm TMA gas. Deposition of ZnO thin film using a RF magnetron sputter was carried out at a pressure of 10 super(-2) Torr in pure oxygen gas with an RF power of 100W. The sensor exhibited a large response to the actual gases produced by a mackerel at an early stage of decomposition.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.456-459
• /
• 2002

This paper describes fabrication and characteristics of ceramic pressure sensor for working at high temperature. The proposed pressure sensor consists of a Ta-N thin-film, patterned on a Wheatstone bridge configuration, sputter deposited onto thermally oxidized Si membranes with an aluminium interconnection layer. The fabricated pressure sensor presents a low temperature coefficient of resistance, high sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.097~1.21mV/$V{\cdot}kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS.

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

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1537-1540
• /
• 2003

MEMS technology with micro scale is complete system utilized as the sensor. micro electro device. The metallization of MEMS is very important to transfer the power operating the sensor and signal induced from sensor part. But in the MEMS structures local stress concentration and deformation is often happened by geometrical shape and different constraint on the metallization. Therefore. this paper studies the effect of supporting type and thickness ratio about thin film thickness of the substrate thickness for the residual stress variation caused by thermal load in the multi-layer thin film. Specimens were made from materials such as Al, Au and Cu and uniform thermal load was applied, repeatedly. The residual stress was measured by FEA and nano-indentation using AFM. Generally, the specimen made of Al induced the large residual stress and the 1st layer made of Al reduced the residual stress about half percent than 2nd layer. Specimen made of Cu and Au being the lower thermal expansion coefficient induce the minimum residual stress. Similarly the lowest indentation length was measured in the Au_Cu specimen by nano-indentation.

• 한국결정성장학회지
• /
• 제20권5호
• /
• pp.221-226
• /
• 2010

메칠멜캅탄($CH_3SH$) 가스를 검출하는 수정진동자(QCM) 가스센서를 QCM의 전극에 $TiO_2$ 나노입자와 전해질 폴리머를 증착하여 제조하였다. LBL-SA법에 의해 제조된 $TiO_2$/PSS 박막은 높은 비표면적을 나타내었고, 가스센서의 감도를 증가시켰다. 1.0 ppm의 농도를 갖는 메칠멜캅탄에 노출된 TEA 혹은 $TiO_2$/PSS 막이 증착된 QCM의 주파수 변이는 각각 약 9 Hz, 2 Hz 였다. ($TiO_2$/PSS) 박막의 증착수가 늘어남에 따라 제조된 박막의 비표면적이 증가하게 되어 QCM 센서의 주파수 변이도 점차적으로 증가하였다. 추가적으로 메칠멜캅탄 가스의 농도가 0.5 ppm에서 2.0 ppm으로 높아짐에 따라 QCM 센서의 주파수 변화도 증가되었다. 본 연구에서는, ($TiO_2$/PSS) 박막이 증착된 QCM 센서의 표면구조의 변화와 센서 특성을 측정하였다.

• 한국재료학회지
• /
• 제13권2호
• /
• pp.111-114
• /
• 2003

Effects of substrate materials on the microstructure and the sensitivity of $SnO_2$thin film gas sensors have been studied. Various substrates were studied, such as oxidized silicon, sapphire, polished alumina, and unpolished alumina. It was observed that strong correlation exists between the electrical resistance and the CO gas sensitivity of the manufactured sensors and the surface roughness of $SnO_2$thin films, which in turn was related to the surface roughness of the original substrates. X$SnO_2$thin film gas sensor on unpolished alumina with the highest surface roughness showed the highest initial resistance and CO gas sensitivity. The transmission electron microscopy observation indicated that shape and size of the columnar microstructure of the thin films were not critically affected by the type of substrates.

• 한국전기전자재료학회논문지
• /
• 제13권7호
• /
• pp.612-616
• /
• 2000

This paper describes on the fabrication and characteristics of hot-film type micro-flowsensors integrated with Pt-RTD(resistance thermometer device) and micro-heater on the Si membrane in which MgO thin-film was used as medium layer in order to improve adhesion of Pt thin-film to SiO$_2$layer. The MgO layer improved adhesion of Pt thin-film to SiO$_2$layer without any chemical reactions to Pt thin-film under high annealing temperatures. Output voltages increased due to increase of heat-loss from sensor to external. The output voltage was 82 mV at $N_2$flow rate of 2000 sccm/min heating power of 1.2 W. The response time($\tau$:63%) was about 50 msec when input flow was stepinput