Fatigue and leakage current characteristics of lead free bilayer thin film structures

Multilayer thin films of (Ba0.50Sr0.50)TiO3 (BST) and Ba(Zr0.15Ti0.85)O3 (BZT) were deposited on Pt(111)/SiO2/Si (111) substrates using Pulsed LASER Deposition (PLD) technique. This manuscript reports on the role of a paraelectric layer in the stack of multilayers on certain key aspects related to crystallographic orientation, interface morphology, tunability, and energy storage properties. The incorporation of paraelectric layer is found to strongly influence the electrical properties of a ferroelectric layer whose composition is at the morphotropic phase boundary. A possible methodology to obtain enhanced electrical properties in multilayer structures based on electric field distribution across different layers in the stack is demonstrated. Incorporation of a paraelectric layer results in restricting the migration of oxygen vacancies due to the presence of the internal bias field. Retention of remanent polarization when driven by 109 bipolar switching cycles and other fatigue properties are reported. Leakage current characteristics were evaluated and the fitting of the experimental data with various conduction mechanisms indicate that different mechanisms are responsible for leakage current conduction as a function of bias voltage. A relatively high power density of >12 MW/cm3 with an energy storage density efficiency of >70%, tunability values comparable with multilayer thin films grown on single crystal substrates are some of the attributes of the multilayer structure.