Iridium oxide top electrodes for piezo- and pyroelectric performance enhancements in lead zirconate titanate thin-film devices

Iridium oxide films of various morphologies are produced by manipulating the reactive gas flow rate in a reactive sputtering process. This study explores the benefits of using planar and nanostructured IrOx top electrodes for Pb(Zr0.52Ti0.48)O-3 (PZT) devices employed in piezoelectric and pyroelectric applications in comparison with conventional platinum electrodes. For the first time, the Young's modulus of a planar IrOx thin film was directly measured to be 300 +/- 15 GPa. The piezoelectric performance of devices with planar IrOx showed up to 245% more strain compared to those capped with a Pt electrode. Nanostructured, 2D IrOx platelet networks are observed for films deposited with high oxygen flow rates. The compatibility with various cleanroom processes, such as liftoff, ultrasonic cleaning, and deposition on etched surfaces, is tested for the IrOx nanostructured layers. These films are shown to have low optical reflectivity while retaining good PZT thin-film capacitor polarization and dielectric permittivity. An improved pyroelectric energy harvesting figure of merit by a factor of 2.5x was observed for the IrOx compared to Pt films on the same PZT material.