Comparison between Ir, Ir 0.85 Rh 0.15 and Ir 0.7 Rh 0.3 thin films as electrodes for surface acoustic waves applications above 800 °C in air atmosphere

Abstract In this paper, we investigate the suitability of Ir, Ir 0.85 Rh 0.15 and Ir 0.7 Rh 0.3 thin films as electrodes for surface acoustic waves (SAW devices) applications taking place above 800 °C in air atmosphere. As expected, all films oxidize from 800 °C in IrO 2 or Ir x Rh 1-x O 2 phase. The electrical properties of the latter remain compatible with the design of SAW devices, with a specific electrical resistance of 151 and 100 μΩ·cm for x = 0.7 and x = 0.85 respectively. Moreover, we observe that the Ir x Rh 1-x O 2 phase is much more stable regarding sublimation effect than the IrO 2 phase, highlighting the interest of alloying Ir with Rh for high-temperature applications. SAW devices based on langasite substrate and Ir 0.85 Rh 0.15 electrodes show a very good stability for at least several days at 800 °C in air. In the case of Ir 0.7 Rh 0.3 electrodes, this stability is extended to temperatures up to 900 °C.