Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes

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.This work was partly supported through the EU FP7 project SOI-HITS (No. 288481). MTC thanks the Oppenheimer Trust and the EPSRC IAA for their generous financial support.This is the author accepted manuscript. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/apl/106/19/10.1063/1.4921170

Development of plasmonic MEMS CMOS infrared sensors for occupancy detection

In this paper, we describe the application of novel MEMS CMOS infrared (IR) sensors for developing compact filter-less occupancy detections. Using such sensors we will report the feasibility of this application in terms of the: sensitivity; response time and selectivity with and without the plasmonic structure. Furthermore, we will compare the detection range, field of view and the size of object of these sensors can detect with and without optical lens

A Low-Power, Low-Cost Infra-Red Emitter in CMOS Technology

In this paper, we present the design and characterization of a low-power low-cost infra-red emitter based on a tungsten micro-hotplate fabricated in a commercial 1-μm silicon on insulator-CMOS technology. The device has a 250- μm diameter resistive heater inside a 600- μm diameter thin dielectric membrane. We first present electro-thermal and optical device characterization, long term stability measurements, and then demonstrate its application as a gas sensor for a domestic boiler. The emitter has a dc power consumption of only 70 mW, a total emission of 0.8 mW across the 2.5-15- μm wavelength range, a 50% frequency modulation depth of 70 Hz, and excellent reproducibility from device-to-device. We also compare two larger emitters (heater size of 600 and 1800μ m) made in the same technology that have a much higher infra-red emission, but at the detriment of higher power consumption. Finally, we demonstrate that carbon nanotubes can be used to significantly enhance the thermo-optical transduction efficiency of the emitter

Filterless non-dispersive infra-red gas detection: A proof of concept

For the first time, we demonstrate the detection of carbon dioxide (CO2) using a non-dispersive infra-red (NDIR) technique that does not require an expensive CMOS-incompatible optical filter. This is achieved by employing a differential IR thermopile detector with micro-engineered (plasmonic) optical properties, fabricated in a commercially available standard CMOS MEMS process. The proof of concept demonstrated here represents a milestone in low-cost gas sensing spectroscopy, and has the potential to impact profoundly in the entire IR field; many consumer electronics applications (wearables, smartphones, tablets and portable medical devices) will become viable, leading to high volume commercial applications for plasmonic devices

A CMOS-MEMS thermopile with an integrated temperature sensing diode for mid-IR thermometry

In this paper, we describe an infrared thermopile sensor comprising of single crystal silicon p+ and n+ elements, with an integrated diode temperature sensor fabricated using a commercial SOI-CMOS process followed by Deep Reactive Ion Etching (DRIE). The chip area is 1.16 mm × 1.06 mm. The integrated diode, being on the same substrate, allows a more localized measurement of the cold junction temperature compared to a conventional external thermistor. The use of single crystal silicon allows good process control and reproducibility from device-to-device in terms of both Seebeck coefficient and sensor resistance. The device has a measured responsivity of 23 V/W, detectivity of 0.75 × 108cm√Hz/W, a 50 % modulation depth of 60 Hz and shows enhanced responsivity in the 8 - 14 μm wavelength range, making it particularly suitable for thermometry applications

Partial characterization and phagocytosis activity of water soluble polysaccharides from Plantago ciliata seeds

International audienc

A highly efficient CMOS nanoplasmonic crystal enhanced slow-wave thermal emitter improves infrared gas-sensing devices

The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoffa € s law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based thermal emitter, fabricated in an industrial CMOS process, and demonstrate its markedly improved practical use in a prototype non-dispersive infrared (NDIR) gas-sensing device. We show that the emission intensity of the thermal emitter at the CO 2 absorption wavelength is enhanced almost 4-fold compared to a standard non-plasmonic emitter, which enables a proportionate increase in the signal-to-noise ratio of the CO 2 gas sensor