Development of NiO-based thin film structures as efficient H2 gas sensors operating at room temperatures |
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Authors: | Nikos Brilis Chara Foukaraki Dimitris Tsamakis |
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Affiliation: | a School of Electrical Engineering and Computer Science, National Technical University of Athens, Iroon Polytechniou 9 Zografou, 15780 Athens, Greece b Theor. and Phys./Chem. Institute, National Hellenic Research Foundation, 11635 Athens, Greece c School of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou 9 Zografou, 15780 Athens, Greece |
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Abstract: | P-type NiO thin films have been developed on high resistivity Si and SiO2 substrates by a pulsed laser deposition technique using an ArF? 193 nm excimer laser at deposition temperature of 300 °C and in 40 Pa partial oxygen pressure. Structures based on such NiO films as host material in the form of Au-NiO Schottky diodes have been subsequently developed under vacuum. In a different procedure, an n-SnO2 layer has been deposited by a CVD technique on a NiO film to produce a p/n heterojunction. The sensing properties of all above structures have been tested upon exposure to a H2 flow in air ambient gas at various operating temperature ranging from 30 to 180 °C. For the NiO films, the optimum temperature was about 150 °C exhibiting a sensitivity of 94%. After surface sensitization of NiO by Au the NiO films showed an H2 response at operating temperature of 30 °C. The sensitivity of p-NiO/n-SnO2 heterojunction devices was extracted from I-V measurements in air and under H2 flow mixed in air. In this case a dramatic increase of the sensitivity was achieved at operating temperature of 30 °C for a forward bias of 0,2 V. |
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Keywords: | Thin films Hydrogen sensing Nickel oxide P-N hetero-junctions Tin oxide Au surface sensitization |
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