title: Behavior of platinum/tantalum as interdigital transducers for SAW devices in high-temperature environments.
abstract: In this paper, we report on the use of tantalum as adhesion layer for platinum electrodes used in high-temperature SAW devices based on langasite substrates (LGS). Tantalum exhibits a great adhesive strength and a very low mobility through the Pt film, ensuring a device lifetime at 900°C of about one hour in an air atmosphere and at least 20 h under vacuum. The latter is limited by morphological modifications of platinum, starting with the apparition of crystallites on the surface, followed by important terracing and breaking of the film continuity. Secondary neutral mass spectroscopy (SNMS), Auger electron spectroscopy (AES), X-ray diffraction (XRD) measurements, and comparison with iridium-based electrodes allowed us to show that this deterioration is likely intrinsic to platinum film, consisting of agglomeration phenomena. Finally, based on these results, we present a solution that could significantly enhance the lifetime of Pt-based IDTs placed in high-temperature conditions.
authors.affiliation: Institut Jean Lamour, UMR 7198, Centre National de la Recherche Scientifique (CNRS) Nancy University, Vandoeuvre lès Nancy, France. thierry.aubert@lpmi.uhp-nancy.fr
authors.forename: Thierry
authors.initials: T
authors.lastname: Aubert
authors.forename: Omar
authors.initials: O
authors.lastname: Elmazria
authors.forename: Badreddine
authors.initials: B
authors.lastname: Assouar
authors.forename: Laurent
authors.initials: L
authors.lastname: Bouvot
authors.forename: Michel
authors.initials: M
authors.lastname: Hehn
authors.forename: Sylvain
authors.initials: S
authors.lastname: Weber
authors.forename: Mourad
authors.initials: M
authors.lastname: Oudich
authors.forename: Damien
authors.initials: D
authors.lastname: Genève