Ferroelectric and dielectric properties of Ca-doped and Ca-Ti co-doped KNaNbO thin films

Chemical solution deposition (CSD) of K 0.5 Na 0.5 NbO 3 (KNN) thin films on silicon-based substrates is an interesting technology for fabrication of lead-free ferroelectric thin films. Here, we report on improved ferroelectric and dielectric properties of KNN thin films prepared by CSD through Ca 2+ -doping and Ca 2+ -Ti 4+ (CaTiO 3 ) co-doping. Undoped KNN, 0.5 mol% Ca 2+ -doped and 0.5 mol% CaTiO 3 -doped KNN films were deposited on platinized silicon substrates by aqueous CSD. X-ray diffraction of the films as well as powders, prepared from the precursor solutions, confirmed that the three KNN materials were single phase solid solutions. A smaller grain size was observed for the doped relative to undoped KNN films. In contrast to the pure KNN films, the Ca 2+ - and CaTiO 3 -doping was observed to promote ferroelectric switching, with a low leakage current and remnant polarization of 6.37 ± 0.47 and 7.40 ± 0.09 μC cm −2 of the Ca 2+ - and CaTiO 3 -doped films, respectively. The dielectric constants of the films were among the highest measured for KNN films from CSD and span from 1800 to 3200 at 1 kHz. Doped K 0.5 Na 0.5 NbO 3 films with good ferroelectric and dielectric properties were prepared by aqueous chemical solution deposition on platinized Si substrates.