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Integrating metal-oxide-decorated CNT networks with a CMOS readout in a gas sensor.

Lee H, Lee S, Kim DH, Perello D, Park YJ, Hong SH, Yun M, Kim S - Sensors (Basel) (2012)

Bottom Line: The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy.The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way.The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Seoul National University, Seoul, Korea. hyunjoong.lee@amic.snu.ac.kr

ABSTRACT
We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures.

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(a) Response of the CNT-network cells to 1,000 ppm of NH3 at 100 °C: individual reaction rates of 77 cells. (b) Response of CNT-SnO2 network cells to 1,000 ppm of NH3 gas at 100 °C: individual reaction rates of 83 cells. (c) Distribution of the sensitivity of the CNT-network cells and the CNT-SnO2 network cells. (d) Distribution of the recovery rates of the CNT-network cells and the CNT-SnO2 network cells.
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f11-sensors-12-02582: (a) Response of the CNT-network cells to 1,000 ppm of NH3 at 100 °C: individual reaction rates of 77 cells. (b) Response of CNT-SnO2 network cells to 1,000 ppm of NH3 gas at 100 °C: individual reaction rates of 83 cells. (c) Distribution of the sensitivity of the CNT-network cells and the CNT-SnO2 network cells. (d) Distribution of the recovery rates of the CNT-network cells and the CNT-SnO2 network cells.

Mentions: Figure 11 shows the measured response of the CNT-network cells connected to the ROIC and mounted on the sensor board. The reaction rate ΔR/R0 is the change in resistance of each CNT-network cell divided by its initial resistance. Figure 11(a) shows reaction rates of 77 CNT-network cells. The results from the remaining 48 cells were ignored due to excessive instability and noise. Figure 11(a) indicates that most of the CNT network cells operate as expected, and that their resistance increases when NH3 is introduced into the reaction chamber. However, there is a nontrivial drift that severely inhibits operational capabilities of this sensor, and suggests the network will have a short lifetime.


Integrating metal-oxide-decorated CNT networks with a CMOS readout in a gas sensor.

Lee H, Lee S, Kim DH, Perello D, Park YJ, Hong SH, Yun M, Kim S - Sensors (Basel) (2012)

(a) Response of the CNT-network cells to 1,000 ppm of NH3 at 100 °C: individual reaction rates of 77 cells. (b) Response of CNT-SnO2 network cells to 1,000 ppm of NH3 gas at 100 °C: individual reaction rates of 83 cells. (c) Distribution of the sensitivity of the CNT-network cells and the CNT-SnO2 network cells. (d) Distribution of the recovery rates of the CNT-network cells and the CNT-SnO2 network cells.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376610&req=5

f11-sensors-12-02582: (a) Response of the CNT-network cells to 1,000 ppm of NH3 at 100 °C: individual reaction rates of 77 cells. (b) Response of CNT-SnO2 network cells to 1,000 ppm of NH3 gas at 100 °C: individual reaction rates of 83 cells. (c) Distribution of the sensitivity of the CNT-network cells and the CNT-SnO2 network cells. (d) Distribution of the recovery rates of the CNT-network cells and the CNT-SnO2 network cells.
Mentions: Figure 11 shows the measured response of the CNT-network cells connected to the ROIC and mounted on the sensor board. The reaction rate ΔR/R0 is the change in resistance of each CNT-network cell divided by its initial resistance. Figure 11(a) shows reaction rates of 77 CNT-network cells. The results from the remaining 48 cells were ignored due to excessive instability and noise. Figure 11(a) indicates that most of the CNT network cells operate as expected, and that their resistance increases when NH3 is introduced into the reaction chamber. However, there is a nontrivial drift that severely inhibits operational capabilities of this sensor, and suggests the network will have a short lifetime.

Bottom Line: The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy.The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way.The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Seoul National University, Seoul, Korea. hyunjoong.lee@amic.snu.ac.kr

ABSTRACT
We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures.

Show MeSH