CUED Publications database

Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes

De Luca, A and Cole, MT and Hopper, RH and Boual, S and Warner, JH and Robertson, AR and Ali, SZ and Udrea, F and Gardner, JW and Milne, WI (2015) Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes. Applied Physics Letters, 106. ISSN 0003-6951

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© 2015 AIP Publishing LLC. In this letter, we present a fully complementary-metal-oxide-semiconductor (CMOS) compatible microelectromechanical system thermopile infrared (IR) detector employing vertically aligned multi-walled carbon nanotubes (CNT) as an advanced nano-engineered radiation absorbing material. The detector was fabricated using a commercial silicon-on-insulator (SOI) process with tungsten metallization, comprising a silicon thermopile and a tungsten resistive micro-heater, both embedded within a dielectric membrane formed by a deep-reactive ion etch following CMOS processing. In-situ CNT growth on the device was achieved by direct thermal chemical vapour deposition using the integrated micro-heater as a micro-reactor. The growth of the CNT absorption layer was verified through scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The functional effects of the nanostructured ad-layer were assessed by comparing CNT-coated thermopiles to uncoated thermopiles. Fourier transform IR spectroscopy showed that the radiation absorbing properties of the CNT adlayer significantly enhanced the absorptivity, compared with the uncoated thermopile, across the IR spectrum (3 μm-15.5 μm). This led to a four-fold amplification of the detected infrared signal (4.26 μm) in a CO < inf > 2 < /inf > non-dispersive-IR gas sensor system. The presence of the CNT layer was shown not to degrade the robustness of the uncoated devices, whilst the 50% modulation depth of the detector was only marginally reduced by 1.5 Hz. Moreover, we find that the 50% normalized absorption angular profile is subsequently more collimated by 8°. Our results demonstrate the viability of a CNT-based SOI CMOS IR sensor for low cost air quality monitoring.

Item Type: Article
Divisions: Div B > Solid State Electronics and Nanoscale Science
Div B > Electronics, Power & Energy Conversion
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:10
Last Modified: 24 May 2018 02:00