Influence of tensile vs. compressive stress on fatigue of lead zirconate titanate thin films

Novel applications of ferroelectric films require a variety of different substrates, which exert different mechanical stress on the film. This raises the question of reliability of differently stressed films. This work compares the cycling-induced fatigue of the polarization hysteresis of PZT films in different stress states. A tensile stress of +270 MPa, for PZT on fused silica glass, causes gradual degradation, while degradation sets in abruptly under compressive stress of -100 MPa, for PZT on sapphire. The main fatigue mechanism is domain wall pinning on charged defects. Reversible and irreversible domain wall processes in the small- and large-signal permittivity reveal that the fatigue behavior results from a variation of the ferroelectric domain structure. Films under tensile stress contain more 90 degrees domain walls, which get pinned continuously on isolated defects. Compressive stress creates more 180 degrees domain walls, which require formation of defect agglomerates during a certain threshold cycle number for pinning.

Automated summary

Novel applications of ferroelectric films require different substrates that exert varying mechanical stress on the film, leading to questions about the reliability of differently stressed films. This study compares the fatigue behavior of PZT films under different stress states, revealing that tensile stress causes gradual degradation while compressive stress leads to abrupt degradation. The main fatigue mechanism is domain wall pinning on charged defects.