• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.63-68
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• 2005

The nano-grained Pd or Pt-doped $SnO_{2}$ thin films were deposited on the alumina substrate at ambient temperature or $300^{\circ}C$ by using an R.F. magnetron sputtering system and then annealed at $650^{\cir}C$ for 1 hour or 4 hours in air. The crystallinity and microstructure of the annealed films were analyzed. A grain size of the thin films was 30 nm to 50 nm. As a result of gas sensitivity measurements to an alcohol vapor of $36^{\circ}C$, the 2 wt.% Pt-doped $SnO_{2}$ thin-film sensor deposited at $300^{\circ}C$ and annealed at $650^{\circ}C$ for 4 hours showed the highest sensitivity.

• Journal of Sensor Science and Technology
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• v.13 no.1
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• pp.41-46
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• 2004

There is currently much interest in the development of instruments that emulate the senses of humans. Increasingly, there is demand for mimicking the human sense of smell, which is a sophisticated chemosensory system. An electronic nose system is applicable to a large area of industries including environmental monitoring. We have designed a protable electronic nose system using an array of commercial chemical gas sensors for recognizing and analyzing the various odours. In this paper, we have implemented a portable electronic nose system using an array of gas sensors for recognizing and analyzing VOCs (Volatile Organic Compounds) in the field. The accuracy of a portable electronic nose system may be lower than an instrument such as GC/MS (Gas Chromatography/Mass Spectrometer). However, a portable electronic nose system could be used on the field and showed fast response to pollutants in the field. Several different algorithms for odours recognition were used such as BP (Back-Propagation) or LM-BP (Levenberq-Marquardt Back-Propagation). We applied RBF (Radial Basis Function) Network for recognition and quantifying of odours, which has simpler and faster compared to the previously used algorithms such as BP and LM-BP.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.348-352
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• 2022

Hydrogen gas (H₂) which is odorless, colorless is attracting attention as a renewable energy source in varions applications but its leakage can lead to disastrous disasters, such as inflammable, explosive, and narcotic disasters at high concentrations. Therefore, it is necessary to develop H₂ gas sensor with high performance. In this paper, we confirmed that H₂ gas detection ability of SnO₂ based H₂ gas sensor along with thermal treatment effect of SnO₂. Proposed SnO₂ based H₂ gas sensor is fabricated by MEMS technologies such as photolithgraphy, sputtering and lift-off process, etc. Deposited SnO₂ thin films are thermally treated in various thermal treatement temperature in range of 500-900 ℃ and their H₂ gas detection ability is estimatied by measuring output current of H₂ gas sensor. Based on experimental results, fabricated H₂ gas sensor with SnO₂ thin film which is thermally treated at 700 ℃ has a superior H₂ gas detection ability, and it can be expected to utilize at the practical applications.

• Journal of Sensor Science and Technology
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• v.20 no.5
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• pp.294-299
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• 2011

$SnO_2$ nanoparticles were synthesized by a hydrothermal method and gas sensors were fabricated using nanoparticles to detect dimethyl methylphosphonate(DMMP) gas. The prepared $SnO_2$ nanoparticles exhibited a high response(72 at $500^{\circ}C$) to 5 ppm DMMP gas compared to commercial $SnO_2$ nanopowders, but their recovery was relatively poor. Various metals(Ni, Sb, Nb) were added to the $SnO_2$ nanoparticles to improve their recovery properties. The focus of this study was to investigate the effects of metal oxide additives on DMMP sensing behavior in $SnO_2$ nanoparticles.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.25.2-25.2
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• 2011

The tungsten oxide wire-like nanostructure is fabricated by deposition and thermal oxidation of tungsten metal on porous single wall carbon nanotubes (SWNTs). The morphology and crystalline quality of materials are investigated by SEM, TEM, XRD and Raman analysis. The results prove that $WO_3$ wire-like nanostructure fabricated on SWNTs show highly porous structures. Exposure of the sensors to NH3 gas in the temperature range of 150~300$^{\circ}C$ resulted in the highest sensitivity at $250^{\circ}C$ with quite rapid response and recovery time. Response time as a function of test concentrations and NH3 gas sensing mechanism is reported and discussed.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.457-461
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• 2006

To use the porous silicon as gas sensors, we made the MOPS structure from the porous silicon with Al evaporation and investigated the sensing characteristic of ethanol. When the MOPS structure is in contact with ethanol gas, the maximum peak of PL changes and it return to original intensity without contact. The MOPS structure had response time 0.78s and recovery time 4.13s when it is in contact with ethanol, which satisfied the required sensor standards. Further complimentary researches, however, are required to investigate the contact mechanism between MOPS structure and ethanol and to solve the surface contamination problem.

• Korean Journal of Materials Research
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• v.16 no.8
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• pp.503-510
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• 2006

The measurement of specific gases is based on the reversible conductivity change of sensing materials in semiconductor type gas sensors. For an application as gas sensors of high sensitivity, porous $SnO_2$ films have been fabricated by anodizing of pure Sn foil in oxalic acid and characteristics of anodic tin oxide films have been investigated. Pore diameter and distribution were dependent on process conditions such as electrolyte concentration, applied voltage, anodizing temperature, and time. Characteristics of anodic films were explained with current density-time curves.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.280-284
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• 2011

Silicon carbide (SiC)-based gas sensors can be operated at very high temperatures. So far, catalytic metal-schottky diodes respond fast to a change between a reducing and an oxidizing atmosphere. Therefore SiC diodes have been suggested for high temperature gas sensor applications. In this work, the effect of reactivity of the catalytic surface on the 4H-SiC sensor-structures in 375 K~775 K have been studied and some fundamental simulations have also been performed.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1867-1872
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• 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.

• Korean Journal of Materials Research
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• v.26 no.9
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• pp.468-471
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• 2016

$SnO_2:CNT$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and were annealed at $300^{\circ}C$ in air. The nano $SnO_2$ powders were prepared by solution reduction method using tin chloride ($SnCl_2.2H_2O$), hydrazine ($N_2H_4$) and NaOH. Nano $SnO_2:CNT$ sensing materials were prepared by ball-milling for 24h. The weight range of CNT addition on the $SnO_2$ surface was from 0 to 10 %. The structural and morphological properties of these sensing material were investigated using X-ray diffraction and scanning electron microscopy and transmission electron microscope. The structural properties of the $SnO_2:CNT$ sensing materials showed a tetragonal phase with (110), (101), and (211) dominant orientations. No XRD peaks corresponding to CNT were observed in the $SnO_2:CNT$ powders. The particle size of the $SnO_2:CNT$ sensing materials was about 5~10 nm. The sensing characteristics of the $SnO_2:CNT$ thick films for 5 ppm $H_2S$ gas were investigated by comparing the electrical resistance in air with that in the target gases of each sensor in a test box. The results showed that the maximum sensitivity of the $SnO_2:CNT$ gas sensors at room temperature was observed when the CNT concentration was 8wt%.