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Chemosensors 2019, 7(1), 12; https://doi.org/10.3390/chemosensors7010012

Porous Gig-Lox TiO2 Doped with N2 at Room Temperature for P-Type Response to Ethanol

1
National Research Council-Institute for Microelectronics and Microsystems (CNR-IMM), Zona Industriale—Strada VIII n°5, 95121 Catania, Italy
2
STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy
3
Dipartimento di Scienze Chimiche, Università degli Studi di Catania and INSTM UdR Catania, Viale Andrea Doria 6, 95125 Catania, Italy
4
Institut Matériaux Microélectronique Nanosciences de Provence (IM2NP) Aix-Marseille Université, 13397 Marseille CEDEX 20, France
*
Author to whom correspondence should be addressed.
Received: 23 January 2019 / Revised: 28 February 2019 / Accepted: 5 March 2019 / Published: 12 March 2019
(This article belongs to the Special Issue Nanotechnology Efforts for Chemical Sensors)
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Abstract

Nanostructured materials represent a breakthrough in many fields of application. Above all for sensing, the use of nanostructures with a high surface/volume ratio is strategic to raise the sensitivity towards dangerous environmental gas species. A new Dc-Reactive sputtering Deposition method has been applied to grow highly porous p-type nitrogen-doped titanium oxide layers by modifying the previously developed reactive sputtering method called gig-lox. The doping of the films was achieved at room temperature by progressive incorporation of nitrogen species during the deposition process. Two different amounts of N2 were introduced into the deposition chamber at flow rates of 2 and 5 standard cubic centimeter per minutes (sccm) for doping. It has been found that the N2 uptake reduces the deposition rate of the TiO2 film whilst the porosity and the roughness of the grown layer are not penalized. Despite the low amount of N2, using 2 sccm of gas resulted in proper doping of the TiO2 film as revealed by XPS Analyses. In this case, nitrogen atoms are mainly arranged in substitutional positions with respect to the oxygen atoms inside the lattice, and this defines the p-type character of the growing layer. Above this strategic structural modification, the multibranched spongy porosity, peculiar of the gig-lox growth, is still maintained. As proof of concept of the achievements, a sensing device was prepared by combining this modified gig-lox deposition method with state-of-the-art hot-plate technology to monitor the electrical response to ethanol gas species. The sensor exhibited a sensitivity of a factor of ≈2 to 44 ppm of ethanol at ≈200 °C as measured by a rise in the layer resistivity according to the p-type character of the material. At the higher temperature of ≈350 °C, the sensor turned to n-type as without doping. This behavior was related to a loss of nitrogen content inside the film during the annealing. It was indeed proved that p-type doping of a gig-lox sponge during growth is feasible, even at room temperature, without losing the layer porosity and the capability to host and detect environmental species. Moreover, the material integration on a device is simply done as the last production step. Easy TiO2 doping procedures, combined with porosity, are of general purpose and interest for several applications even on flexible substrates. View Full-Text
Keywords: gas sensor; titanium oxide; doping; nitrogen gas sensor; titanium oxide; doping; nitrogen
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Smecca, E.; Sanzaro, S.; Galati, C.; Renna, L.; Gervasi, L.; Santangelo, A.; Condorelli, G.G.; Grosso, D.; Bottein, T.; Mannino, G.; La Magna, A.; Alberti, A. Porous Gig-Lox TiO2 Doped with N2 at Room Temperature for P-Type Response to Ethanol. Chemosensors 2019, 7, 12.

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