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Article Dans Une Revue IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Année : 2012

Investigations on AlN/Sapphire piezoelectric bilayer structure for high-temperature SAW applications

Thierry Aubert
Omar Elmazria
Badreddine Assouar
Ahmad Hamdan

Résumé

This paper explores the possibility of using AlN/ sapphire piezoelectric bilayer structures for high-temperature SAW applications. To determine the temperature stability of AlN, homemade AlN/sapphire samples are annealed in air at- mosphere for 2 to 20 h at temperatures from 700 to 1000°C. Ex situ X-ray diffraction measurements reveal that the micro- structure of the thin film is not affected by temperatures below 1000°C. Ellipsometry and secondary ion mass spectroscopy in- vestigations attest that AlN/sapphire is reliable up to 700°C. Beyond this temperature, both methods indicate ongoing sur- face oxidation of AlN. Additionally, Pt/Ta and Al interdigi- tal transducers are patterned on the surface of the AlN film. The resulting SAW devices are characterized up to 500°C and 300°C, respectively, showing reliable frequency response and a large, quasi-constant temperature sensitivity, with a first-or- der temperature coefficient of frequency around −75 ppm/°C. Between room temperature and 300°C, both electromechani- cal coupling coefficient K2 and propagation losses increase, so the evolution of delay lines' insertion losses with temperature strongly depends on the length of the propagation path.
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hal-00783993 , version 1 (20-02-2023)

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Thierry Aubert, Omar Elmazria, Badreddine Assouar, Eloi Blampain, Ahmad Hamdan, et al.. Investigations on AlN/Sapphire piezoelectric bilayer structure for high-temperature SAW applications. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2012, 59 (5), pp.999 - 1005. ⟨10.1109/TUFFc.2012.2285⟩. ⟨hal-00783993⟩
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