Thermal Shock and Thermal Fatigue of Ferroelectric Thin Film due to Pulsed Laser Heating

Abstract

Thermal shock and thermal fatigue of ferroelectric (FE) thin films were investigated by the pulsed laser tests. The power density was gradually increasing in the single pulsed laser heating test which simulated a thermal shock, the part melting threshold of Pb(Zr0.52Ti0.48)O3 (PZT) thin films was found by scanning electron microscopy (SEM). After thermal shock resulted the highest temperature below Curie point at the surface of PZT thin film, X-ray diffraction (XRD), SEM and RT66A standard ferroelectrics analyzer were used to study the microstructure, crystal grain sizes, and ferroelectric failure behavior. It was found that XRD peak of PZT thin film after laser beam heating was stronger than that before laser beam heating, crystal grain sizes decreased, and the ferroelectric properties were degraded. However there was no crack observed by SEM, until PZT thin films were melted. The fined grain effects on ferroelectric properties and XRD patterns of PZT thin film, depolarization due to the single pulsed laser heating were discussed respectively. The pulsed cycles with a certain power density were gradually increasing in the repetition pulsed laser heating test. It was interesting to find that the cracks will initiate and propagate due to the thermal fatigue induced by the repetition pulsed laser. The possible origins of the thermal fatigue cracks were also discussed.