Pulsed Laser Deposition of Piezoelectric Ba0.85Ca0.15Ti0.9Zr0.1O3 Thin Films on Various Electrode/Substrate Combinations

Abstract Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) lead-free thin films (400 nm thick) with a tetragonal structure were grown by pulsed laser deposition on various bottom electrode/substrate sets. High-resolution X-ray diffraction confirmed heteroepitaxial growth of BCTZ on (001)-oriented SrTiO3 substrates; in contrast, films fabricated on LaNiO3, La0.5Sr0.5Co3, SrRuO3, Pt, and Pt/Ti electrodes (on SrTiO3, LaAlO3, Si, and Si/SiO2 substrates) were found to be highly (001)-preferentially oriented or polycrystalline. Thermodiffraction experiments revealed a change in the thermal expansion coefficient around 100 °C, characteristic of the ferroelectric-to-paraelectric Curie phase transition in BCTZ films. For all studied configurations, BCTZ films on LaNiO3 electrodes demonstrated superior piezoelectric and ferroelectric properties. The highest macroscopic effective piezoelectric coefficient (d33eff = 38 pm·V–1) was achieved for polycrystalline BCTZ films grown on LaNiO3/Si. However, the nanoscale measurement recorded via atomic force microscopy showed the narrowest distribution of both coercive voltage and electromechanical response for (001)-oriented films on LaNiO3/SrTiO3. Using an LaNiO3 electrode, the contribution of leakage current was significantly reduced, compared to LSCO, achieving 2 Pr ≈ 5.8 μC·cm–2 under 13 V and 2 Vc ≈ 2.9 V for a BCTZ film grown on LaNiO3/SrTiO3. As a result, LaNiO3 is identified to be the most suitable electrode for enhancing performances of BCTZ thin films. In view of the results, BCTZ/LaNiO3 was grown on a cost-effective insulating polycrystalline Al2O3 substrate, and the obtained piezoelectric results deserve interest.