Ir-Rh thin films as high-temperature electrodes for surface acoustic wave sensor applications

Abstract : The achievement of surface acoustic wave (SAW) devices stable in high-temperature oxidizing atmospheres requires the development of conductive thin film electrodes that can withstand such harsh conditions. Recent studies have demonstrated the suitability of Pt-based alloys, multilayers or nanocomposite films for temperatures up to 800 °C. Electrodes based on new materials and structures still have to be developed for applications taking place at higher temperatures. In this perspective, thin films based on iridium could be good candidates regarding the high melting point, and thus the low diffusion coefficients of this noble metal. In particular, Ir-Rh bulk alloys have shown superior performance as spark plug electrodes, which have to resist concurrently to physical and chemical wear such as high-temperature SAW electrodes. Consequently, this paper deals with the high-temperature behavior of Ir-Rh thin films. Ir-Rh alloys and multilayers films, with an Ir atomic ratio between 10 and 50%, are deposited by one-gun electron beam evaporation method. The impact on the films of a 4-days annealing treatment at 800 °C in air is studied by X-ray diffraction, scanning and transmission electron microscopy, electron energy loss spectroscopy and four-points probe resistivity measurements. It turns out that all the films oxidized during the annealing period. The post-annealing electrical properties are highly dependent of the initial composition of the film: the higher is the Ir rate in the film, the lower is the electrical resistivity after annealing. Moreover, an Rh2O3 overlayer, with a thickness of some tens of nanometers, forms at the surface of the film, confirming previous observations made on Ir-Rh bulk alloys. First SAW measurements made on devices based on Ir30Rh70 alloy electrodes are very promising as a SAW signal is still clearly visible after the 4-days annealing process, while no agglomeration phenomenon can be observed.
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Sensors and Actuators A: Physical , Elsevier, 2016, 〈10.1016/j.sna.2016.03.008〉
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Contributeur : Sébastien Van Luchene <>
Soumis le : mardi 15 mars 2016 - 17:50:52
Dernière modification le : jeudi 5 avril 2018 - 12:30:21

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Amine Taguett, Thierry Aubert, Marc Lomello, Ouarda Legrani, Omar Elmazria, et al.. Ir-Rh thin films as high-temperature electrodes for surface acoustic wave sensor applications. Sensors and Actuators A: Physical , Elsevier, 2016, 〈10.1016/j.sna.2016.03.008〉. 〈hal-01288956〉

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