Comparing macroscopic and microscopic properties of seeded ferroelectric thin films

Abstract

The comparison of macroscopic and microscopic properties of ferroelectric thin films in the systems of lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) with and without seeds is carried out. Microscopic properties were studied by piezo-response force microscopy (PFM). The local piezoelectric properties with and without seeds are compared with their macroscopic electric properties measured by conventional techniques. Previous microstructure analysis of PZT thin films showed that an intermetallic Pt _x Pb layer between PZT and Pt, formed during the annealing process, was reduced and even eliminated in seeded PZT films. In SBT films, the addition of SBT seeds suppressed the interdiffusion of Pt and film components. Hence, the interfaces of PZT/substrate and SBT/substrate are modified by the presence of seeds, and their electrical properties are improved. In both PZT and SBT films, the remanent polarization values are higher in seeded films than in unseeded ones. Similarly, local piezo-response signal of single grain showed higher longitudinal piezoelectric coefficient d ₃₃ in seeded films than in unseeded ones. The critical voltage in which the ferroelectric domain starts to switch is lower in seeded films than in unseeded ones. The analysis of nanoscale switching in PZT and SBT films by PFM is presented and related to the corresponding macroscopic electric properties.