Low-Temperature-Grown KNbO₃ Thin Films and Their Application to Piezoelectric Nanogenerators and Self-Powered ReRAM...

Amorphous KNbO₃ (KN) film containing KN nanocrystals was grown on TiN/SiO₂/Si substrate at 350 °C. This KN film showed a dielectric constant (ε_r) and a piezoelectric strain constant (d₃₃) of 43 and 80 pm/V at 10 V, respectively, owing to the existence of KN nanocrystals. Piezoelectric nanogenerators (PNGs) were fabricated using KN films grown on the TiN/polyimide/poly(ethylene terephthalate) substrates. The PNG fabricated with the KN film grown at 350 °C showed an open-circuit output voltage of 2.5 V and a short-circuit current of 70 nA. The KN film grown at 350 °C exhibited a bipolar resistive switching behavior with good reliability characteristics that can be explained by the formation and rupture of the oxygen vacancy filaments. The KN resistive random access memory device powered by the KN PNG also showed promising resistive switching behavior. Moreover, the KN film shows good biocompatibility. Therefore, the KN film can be used for self-powered biomedical devices.