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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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Optical image of the CNT ROIC die.
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f3-sensors-12-02582: Optical image of the CNT ROIC die.

Mentions: The CNT ROIC chip was fabricated using a 0.35 μm CMOS process, as shown in the photograph in Figure 3. Integrating the CNT networks and the ROIC on the same die is done by locating the CNT cells on the left-had side of the ROIC, while the pads are located on the right. With this layout, it is possible to dip the cells into the CNT solution as described above, while the keeping the pads above the liquid to avoid introducing shorts between them. The CNT ROIC die is then connected to the PCB using the chip-on-board process, with the CNT sensor cells remaining exposed to react with gas. Figure 4 shows the arrangements for testing the CNT ROIC. The experimental sensing setup utilizes mass flow controllers interfaced to a computer and a 38 mm diameter quartz reaction tube. The circuit is powered via a USB connection to the computer, which serves as both a 5 V power supply and data interface. In this manner, air (21% O2/N2, 99.999%) with or without 1,000 ppm of NH3 gas can be introduced into a temperature-controlled environment while performing electrical characterization. This arrangement also promotes uniform flow across the array of CNT cells, which was fixed at 500 cm3/s.


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)

Optical image of the CNT ROIC die.
© Copyright Policy
Related In: Results  -  Collection

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

f3-sensors-12-02582: Optical image of the CNT ROIC die.
Mentions: The CNT ROIC chip was fabricated using a 0.35 μm CMOS process, as shown in the photograph in Figure 3. Integrating the CNT networks and the ROIC on the same die is done by locating the CNT cells on the left-had side of the ROIC, while the pads are located on the right. With this layout, it is possible to dip the cells into the CNT solution as described above, while the keeping the pads above the liquid to avoid introducing shorts between them. The CNT ROIC die is then connected to the PCB using the chip-on-board process, with the CNT sensor cells remaining exposed to react with gas. Figure 4 shows the arrangements for testing the CNT ROIC. The experimental sensing setup utilizes mass flow controllers interfaced to a computer and a 38 mm diameter quartz reaction tube. The circuit is powered via a USB connection to the computer, which serves as both a 5 V power supply and data interface. In this manner, air (21% O2/N2, 99.999%) with or without 1,000 ppm of NH3 gas can be introduced into a temperature-controlled environment while performing electrical characterization. This arrangement also promotes uniform flow across the array of CNT cells, which was fixed at 500 cm3/s.

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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