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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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CNT network initial resistances. (a) Distribution of initial resistance for the bare CNT networks. (b) Distribution of initial resistance for the SnO2-decorated CNT networks.
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f2-sensors-12-02582: CNT network initial resistances. (a) Distribution of initial resistance for the bare CNT networks. (b) Distribution of initial resistance for the SnO2-decorated CNT networks.

Mentions: Figure 2 shows the distribution of initial resistance for the bare CNT networks and the SnO2-decorated networks. We see that the initial resistances of individual sensors are increased by the decoration processes, and that they are also widely distributed. Fully determining the reasons for these changes is beyond the scope of this paper, but we speculate that two factors are involved: the depletion of charge in the CNTs and added charge centers after SnO2 deposition. CNTs are extremely sensitive to the addition of environmental charge centers, resulting in decreased current and trap-assisted conductivity [4–6,15–17]. Although CNT are remarkable resistant to damage via low-energy species [18], there remains the possibility of damage to the CNT networks during SnO2 deposition. These combined factors are likely to obstruct currents flowing across the CNT networks and increase overall resistance.


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)

CNT network initial resistances. (a) Distribution of initial resistance for the bare CNT networks. (b) Distribution of initial resistance for the SnO2-decorated CNT networks.
© Copyright Policy
Related In: Results  -  Collection

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

f2-sensors-12-02582: CNT network initial resistances. (a) Distribution of initial resistance for the bare CNT networks. (b) Distribution of initial resistance for the SnO2-decorated CNT networks.
Mentions: Figure 2 shows the distribution of initial resistance for the bare CNT networks and the SnO2-decorated networks. We see that the initial resistances of individual sensors are increased by the decoration processes, and that they are also widely distributed. Fully determining the reasons for these changes is beyond the scope of this paper, but we speculate that two factors are involved: the depletion of charge in the CNTs and added charge centers after SnO2 deposition. CNTs are extremely sensitive to the addition of environmental charge centers, resulting in decreased current and trap-assisted conductivity [4–6,15–17]. Although CNT are remarkable resistant to damage via low-energy species [18], there remains the possibility of damage to the CNT networks during SnO2 deposition. These combined factors are likely to obstruct currents flowing across the CNT networks and increase overall resistance.

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