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

• Published in: Sensors (Basel, Switzerland) Switzerland), 2012-03, Vol.12 (3), p.2582-2597
• Main Authors: Lee, Hyunjoong, Lee, Sanghoon, Kim, Dai-Hong, Perello, David, Park, Young June, Hong, Seong-Hyeon, Yun, Minhee, Kim, Suhwan
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonia - analysis; Arrays; Carbon; carbon nanotube (CNT); CMOS; Computer engineering; Consumption; Deposition; Electrodes; Electrons; Gas sensors; Gases; Gases - analysis; Integrated circuits; metal decoration; Metals - chemistry; Nanotubes, Carbon - chemistry; Networks; Oxidation; Oxidation-Reduction; Oxides - chemistry; Process controls; read-out integrated circuit; Semiconductors; Sensors; Silicon wafers; single die; Temperature
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s120302582

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.