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Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes
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De Luca, A., Cole, M. T., Hopper, R. H., Boual, S., Warner, J. H., Robertson, A. R., Ali, S. Z., Udrea, F., Gardner, J. W. and Milne, W. I. (2015) Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes. Applied Physics Letters, 106 (19). 194101. doi:10.1063/1.4921170 ISSN 0003-6951.
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Official URL: http://dx.doi.org/10.1063/1.4921170
Abstract
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 CO2 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: | Journal Article | ||||||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering | ||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Engineering > Engineering | ||||||||
Library of Congress Subject Headings (LCSH): | Gas detectors, Metal oxide semiconductors, Complementary, Microelectromechanical systems, Carbon nanotubes | ||||||||
Journal or Publication Title: | Applied Physics Letters | ||||||||
Publisher: | American Institute of Physics | ||||||||
ISSN: | 0003-6951 | ||||||||
Official Date: | 11 May 2015 | ||||||||
Dates: |
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Volume: | 106 | ||||||||
Number: | 19 | ||||||||
Article Number: | 194101 | ||||||||
DOI: | 10.1063/1.4921170 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Funder: | Seventh Framework Programme (European Commission) (FP7), Oppenheimer Trust, Engineering and Physical Sciences Research Council (EPSRC) | ||||||||
Grant number: | 288481 (FP7) |
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