• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.155-162
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• 2002

The sensing properties of carbon monooxide were investigated as a function of mixing ratio and the lamination structure of 3mol% ZnO-doped $SnO_2$ and 3mol% $SnO_2$-doped ZnO. The lamination structures were fabricared monolayer, double layer, and hetero layer of $SnO_2$, Zno, and theirs mixture composition using thick film process. There was no second phase by the reaction of $SnO_2$ and ZnO. The conductance was decreased by the addition of ZnO in $SnO_2$, but it was increased with the addition of $SnO_2$ in ZnO. The conductance was increased with temperature and the inlet of CO. There was no improvement of sensitivity in the structure of mono- and double-layer. The hetero-layer structure, however, of $SnO_2$ 3ZnO-ZnO $3SnO_2$ showed the higher resistivity and the highest sensitivity. Ohmic characteristics was confirmed by the linear properties for I-V measurements.

• Journal of IKEEE
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• v.13 no.4
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• pp.37-42
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• 2009

In this study, nanopower ZnO and $SnO_2$ as sensing materials were prepared by hydrazine and hydrothermal routes, respectively, and were doped with Pd, Ru catalyst. The CO and $NO_2$ sensors were fabricated by coating of sensing materials on the MEMS-based structure with electrodes and heaters. The 0.1 wt% Pd doped $SnO_2$ sensor and Ru doped ZnO sensor showed the high sensor response to CO 30 ppm and $NO_2$ 1 ppm, respectively. The sensor signal was stable. This can be used for the detection of pollutant gases emitted from gasoline engine.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.476-482
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• 1997

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and pattern recognition techniques such as principal component analysis and back-propagation artificial neural network. The sensor array consists of six thick-film gas sensors whose sensing layers are Pd-doped $WO_{3}$, Pt-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$ + Pd coated layer, $Al_{2}O_{3}$-doped ZnO and $PdCl_{2}$-doped $SnO_{2}$. The portable electronic nose system consists of an 16bit Intel 80c196kc as CPU, an EPROM for storing system main program, an EEPROM for containing optimized connection weights of artificial neural network, an LCD for displaying gas concentrations. As an application the system has been used to identify 26 carbon monoxide/hydrocarbon (CO/HC) car exhausting gases in the concentration range of CO 0%/HC 0 ppm to CO 7.6%/HC 400 ppm and the identification has been successfully demonstrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.99-102
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• 1997

An electronic nose system is an instrument designed far mimicking human olfactory system. It consists generally of gas (odor) sensor array corresponding to olfactory receptors of human nose and artificial neural network pattern recognition technique based on human biological odor sensing mechanism. Considerable attempts to develop the electronic nose system have been made far applications in the fields of floods, drinks, cosmetics, environment monitoring, etc. A portable electronic nose system has been fabricated by using oxide semiconductor gas sensor array and pattern recognition technique such as principal component analysis (PCA) and back propagation artificial neural network The sensor array consists of six thick film gas sensors whose sensing layers are Pd-doped WO$_3$ Pt-doped SnO$_2$ TiO$_2$-Sb$_2$O$_3$-Pd-doped SnO$_2$ TiO$_2$-Sb$_2$O$_{5}$-Pd-doped SnO$_2$+Pd filter layer, A1$_2$O$_3$-doped ZnO and PdCl$_2$-doped SnO$_2$. As an application the system has been used to identify CO/HC car exhausting gases and the identification has been successfully demonstrated.d.

• Korean Journal of Materials Research
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• v.33 no.5
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• pp.195-204
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• 2023

Micro-electronic gas sensor devices were developed for the detection of carbon monoxide (CO), nitrogen oxides (NO_x), ammonia (NH₃), and formaldehyde (HCHO), as well as binary mixed-gas systems. Four gas sensing materials for different target gases, Pd-SnO₂ for CO, In₂O₃ for NO_x, Ru-WO₃ for NH₃, and SnO₂-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were then fabricated using a micro sensor platform. The gas sensing behavior and sensor response to the gas mixture were examined for six mixed gas systems using the experimental data in MEMS gas sensor arrays in sole gases and their mixtures. The gas sensing behavior with the mixed gas system suggests that specific adsorption and selective activation of the adsorption sites might occur in gas mixtures, and allow selectivity for the adsorption of a particular gas. The careful pattern recognition of sensing data obtained by the sensor array made it possible to distinguish a gas species from a gas mixture and to measure its concentration.