Fabrication of the transparent ferroelectric heterostructures based on KNN-based lead-free films

Transparent and epitaxial 0.95(K_0.49Na_0.49Li_0.02)(Ta_0.2Nb_0.8)O₃-0.05CaZrO₃ with 2 wt.% MnO₂ addition (KNNLT-CZM) lead-free ferroelectric film heterostructures are fabricated on the La_0.07Ba_0.93SnO₃ (LBSO)-coated SrTiO₃ (001) substrates using pulsed laser deposition. The optical measurements show that these film heterostructures exhibit good transmittance with a maximum transmittance of ∼80%. Temperature-dependent dielectric properties demonstrate that the KNNLT-CZM films possess a high Curie temperature (T _C) above 420 °C, and exhibit an orthorhombic to tetragonal phase transition at ∼170 °C. Furthermore, these film heterostructures also have a large twice remnant polarization of 29.66 μC cm⁻² and well-defined ferroelectric hysteresis loops up to 200 °C. The x-ray photoelectron spectra suggest that partial K elements did not enter in the lattice of the KNNLT-CZM perovskite structure and the Mn dominantly existed in the form of Mn²⁺. The observed good transmittance, high T _C and excellent electrical properties of the LBSO-buffered KNNLT-CZM film heterostructures indicate that these films have great application potential in opto-electronic devices and film transistors. (paper)