Low temperature preparation of KNbO ₃films by hydrothermal method and their characterization

KNbO3 films were prepared at 100 - 240°C on (100)_cSrRuO₃//(100)SrTiO₃ substrates by hydrothermal method using KOH and Nb2O5 as source materials. The incubation time before starting deposition and the deposition rate after starting deposition increased and decreased with decreasing deposition temperature, respectively. Epitaxial {100}c-oriented KNbO3 films with 300 nm thick were successfully obtained at 100°C on (100)cSrRuO₃//(100)SrTiO₃ substrates for 144 h. We observed the typical butterfly-shape strain curves originated from the piezoelectricity for the first time for KNbO3 films deposited down to 120°C.