|Title||Characterization of metal-modified and vertically-aligned carbon nanotube films for functionally enhanced gas sensor applications|
|Publication Type||Articolo su Rivista peer-reviewed|
|Year of Publication||2009|
|Authors||Penza, M., Rossi R., Alvisi Marco, Signore M.A., Cassano Gennaro, Dimaio D., Pentassuglia R., Piscopiello E., Serra Emanuele, and Falconieri M.|
|Journal||Thin Solid Films|
|Keywords||air monitoring, Air pollution, Aligned carbon nanotubes, Alumina substrates, Carbon films, Carbon Nanostructures, Carbon nanotubes, Charge transfer, Charge transfer model, Chemical detection, Chemical sensors, Dense network, Diamond films, Electrical conductance, Ethanol, Fe catalyst, Film growth, Forest-like CNTs, Functionalizations, Functionalized, Gas detection, Gas detectors, Gas sensors, Gases, Hazardous gas, Ion exchange, Multi-walled, Nano-sized, Nanoclusters, P-type, Plasma deposition, Plasma enhanced chemical vapor deposition, Platinum, Radio frequency plasma, Raman spectroscopy, Reducing gas, Rf-PECVD, Scanning electron microscopy, SEM, Sensor networks, silver, Substrate surface, Substrates, TEM, Toluene, Transmission electron microscopy, Tube diameters|
Carbon nanotube (CNT) networked films have been grown by radiofrequency plasma enhanced chemical vapour deposition (RF-PECVD) technology onto low-cost alumina substrates, coated by nanosized Fe-catalyst for growing CNTs, to perform chemical detection of hazardous gases, at an operating sensor temperature in the range 25-150 °C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The carbon nanotubes were "forest-like" with ropes vertically-aligned to the substrate surface. A dense network of bundles of multiple tubes consisting of multi-walled carbon nanostructures appears with a maximum length of 7-10 μm and single-tube diameter varying in the range of 5-35 nm. Surface functionalizations of the vertically-aligned CNT networks with nominally 5 nm thick Pt-, Ru- and Ag-nanoclusters, prepared by magnetron sputtering, provide higher sensitivity for significantly enhanced gas detection of NO2, H2, ethanol and toluene up to a low limit of sub-ppm level. The measured electrical conductance of the functionalized CNTs upon exposures of a given oxidizing and reducing gas is modulated by a charge transfer model with p-type semiconducting characteristics. Functionalized CNT gas sensors exhibited better performances compared to unmodified CNTs, making them highly promising candidates for environmental air monitoring applications, at ppb-level of toxic gas detection. © 2009 Elsevier B.V. All rights reserved.
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