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This work focuses on the development of surface ionization gas sensors based on copper oxide (CuO). CuO nanowires were prepared by thermal oxidation starting from a thin film of metallic copper deposited by RF magnetron sputtering. In addition to the well-known conductimetric sensors, we have developed another kind of device depending upon a different sensing mechanism, namely surface ionization (SI). SI phenomenon involves ions formed by the adsorption of gas molecules on heated solid surface, the electron transfer from the adsorbed species to the electrode surface and the extraction of the ion adsorbates into free space by an external electrical field. Our preliminary results show that humidity plays an important role in the ions formation and so in sensors performance. For this reason we have done a systematic study on the interaction mechanism of target molecules with hydroxyl groups adsorbates on CuO surface, explaining the experimental results in terms of acidity/basicity. [ABSTRACT FROM AUTHOR]

A comparative study of Kelvin Probe (KP) surface work function analysis of p-type CuO thin films to its nanowires is presented. Thin films were prepared by RF magnetron sputtering and nanowires were grown by thermal oxidation of grown thin films. The structural characterization was carried out by SEM and micro-Raman spectrophotometry. Finally, Surface work function variations of both materials were recorded while exposing them to some oxidizing and reducing gases, looking for a comparison between their gas sensing performances. The collected results were analyzed and compared to improve our understanding about sensing mechanisms involved in these kinds of p-type materials. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) mat-based conductometric devices were fabricated using a thermal oxidation technique. A metallic zinc layer was deposited on the alumina transducer and then oxidized in a controlled atmosphere, in order to obtain ZnO nanostructures. Two different batches of sensors have been prepared, and their sensing performances have been evaluated towards oxidizing and reducing gases. Functional measurements showed very good sensing performances towards ethanol and acetone at 500 ° C, and NO2 at 200 ° C, indirectly confirming the n-type behaviour of the material. The influence of the humidity on the response has been explored. In practical conditions the interference of humidity is very small, and could be neglected in many applications. Simultaneous measurements on different devices from the same batch confirm the high reproducibility of the response within the batch. [ABSTRACT FROM AUTHOR]

Abstract: CuO nanowires (NWs) were grown by thermal oxidation of metallic Cu thin layer deposited by sputtering on different substrates. Optimal growth parameters were found, studying the influence of the oxidizing temperature and the atmosphere during the oxidation process. A strong relation between oxidation parameters and morphology has been detected. The preliminary response of this sensing material, using nanowire's mat-based device, to various oxidizing and reducing target gases has been evaluated, in order to corroborate the functional properties of the CuO NWs as potential sensing material under certain conditions and to confirm the p-type conductometric response of the material. [Copyright &y& Elsevier]