We performed the macroscopic electrical characterization of epitaxially grown, compressively strained K 0.7 Na 0.3 NbO 3 thin films (70 nm) on SrRuO 3 / ( 110 ) TbScO 3 substrates, displaying monoclinic Mc domains. Hysteresis measurements revealed ferroelectric behavior up to at least 10 7 cycles at room temperature, with a polarization value ( 2 P ) of 25 µ C / cm 2 . A double-peak switching behavior was observed, attributed primarily to domain-wall pinning/depinning and back switching, with a wake-up effect analogous to that reported in doped hafnium oxide and lead zirconate titanate systems. Temperature-dependent measurements (100 K—300 K) confirm ferroelectricity at low temperatures, while the double-peak behavior becomes less pronounced due to suppression of thermally activated back switching. Capacitance-voltage measurements reveal an increased dielectric response at higher temperatures, consistent with enhanced domain wall mobility. The asymmetry in coercive voltages additionally points to internal bias fields likely arising from electrode interfaces. Our results provide a comprehensive overview of the switching dynamics of strained K 0.7 Na 0.3 NbO 3 films and demonstrate ferroelectricity in the Mc phase.
Guimaraes et al. (Tue,) studied this question.