Ferroelectric properties of Pb(Zr, Ti)O3 thin films deposited on annealed IrO2 and Ir bottom electrodes

Ferroelectric fatigue and hysteresis of reactively sputtered Pb(Zr, Ti)O3 (PZT) thin films were investigated by annealing IrO2 and Ir bottom electrodes at various temperatures. These electrodes were annealed to change their crystallinity and surface morphology in O2 or N2 atmosphere, respectively. There was no appreciable roughening of the PZT/IrO2 interface respective to that of the PZT/Ir; the rms roughness of IrO2 and Ir annealed at 650 °C was about 3.5 and 10 nm, respectively. The ferroelectric properties of the PZT/IrO2 were found to be overall better than those of the PZT/Ir. The PZT/IrO2 thin films exhibited very small fatigue up to 1011 cycles; the P*r-P∧r value decreased only from 16.6 to 14 μC/cm2 until 1012 polarization reversals. This is due to the excellent diffusion barrier property of IrO2 and the smooth PZT/IrO2 interface. On the other hand, although thin IrO2 layer was formed between PZT and Ir, the PZT/Ir thin films began to undergo fatigue after 109 polarization reversals.