Annealing Activation Effect of Pt Electrodes on SAW Devices with Langasite Substrate and the Mechanism Analysis

High-temperature-resistant surface acoustic wave (SAW) devices commonly employ a structure where Pt electrodes are grown on langasite (LGS) substrates. This paper compares the resonance performance of LGS/Pt SAW devices before and after annealing, revealing that devices of this structure require annealing activation to become functional. Comparative experiments with Au electrodes confirm that the annealing process primarily affects the Pt electrodes. Analysis of Pt microstructures before and after annealing reveals the formation of larger, irregular grains in the Pt films, which would lead to changes in their mechanical properties. Nanoindentation testing comparing load-displacement curves suggests that the annealing process may improve performance of SAW devices by relieving residual stresses within the Pt films.