Microstructure, Tunable and Pyroelectric Properties of Laser-Ablated Ba (Zr0.25 Ti0.75) O3 Thin Films

Abstract

Micro-devices such as tunable varactors and infrared sensors have been of great interest in many applications such as wireless communication and thermal imaging. Thin film capacitors made of ferroelectric materials have been widely studied for use as active elements in those devices due to their excellent performances. The application of ferroelectric thin films in infrared sensors is based on the induced pyroelectric effect, while the use of ferroelectric thin films in tunable devices is to take advantage of the dependence of dielectric constant on applied electric field. This research focuses on studying the variations of microstructures and their correlations with the tunable and induced pyroelectric properties of laser-ablated Ba(Zr0.25Ti0.75)O3 thin films deposited on Si-based substrates. The phenomena were investigated under the effects of deposition temperature, post-annealing duration, oxygen pressure, and thickness. It has been found from this research that improved crystallinity of perovskite structure, high degree of orientation in (011) plane, low lattice strain with respect to bulk have resulted in the high dielectric constant, tunability and pyroelectric coefficient. The improved crystallinity and low lattice strain with respect to bulk could be obtained at the high deposition temperature or long annealing duration, while the high degree of orientation in (011) plane and low lattice strain with respect to bulk could be attained at either intermediate oxygen pressure or high film thickness.