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

Abstract

Amorphous KNbO (KN) film containing KN nanocrystals was grown on TiN/SiO/Si substrate at 350 °C. This KN film showed a dielectric constant (ε) and a piezoelectric strain constant (d) 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.

Improvement of Conductance Modulation Linearity in a Cu2+-Doped KNbO3 Memristor through the Increase of the Number of Oxygen Vacancies

“…Therefore, it can be concluded that a crystalline phase was developed in the KN film deposited at 350 °C using PLD. According to a previous study, KN films that were grown by radio frequency (RF) sputtering on TiN electrodes at 350 °C exhibited an amorphous phase containing KN nanocrystals. , Therefore, it is considered that PLD is an effective method to produce a crystalline KN film at a lower temperature compared to RF sputtering and similar results have also been observed for other oxide films. , The crystalline KN memristor displayed a typical I – V curve of a ReRAM memristor with set and reset voltages of −1.2 and 1.5 V, respectively, as shown in Figure c. Currents in the high-resistance state (HRS) and low-resistance state (LRS) can be explained by the space-charge limited current (SCLC) mechanism and Ohmic conduction, respectively (Figure S1a).…”

“…Moreover, the formation and rupture of oxygen vacancy filaments provide the switching mechanism of the crystalline KN memristor (Figure S1b). In addition, a forming process was needed to obtain an I – V curve for the amorphous KN film but the crystalline KN film did not need this forming process, revealing that the formation of oxygen vacancy filaments could be easier in the crystalline KN film than in the amorphous KN film.…”

Sustainable Natural Bio‐Origin Materials for Future Flexible Devices

“…[ 118 ] So far, many attempts had been made to fabricate PENG by employing various materials such as inorganic nanomaterials like BaTiO 3 , [ 119 ] ZnO, [ 120 ] and KNbO 3 . [ 121 ] Piezoelectric organic polymers like poly(vinylidene fluoride) (PVDF) [ 122 ] and poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) [ 123 ] are also widely utilized for fabricating flexible PENG for wearable applications. Nevertheless, most polymer‐based piezoelectric material exhibits bad piezoelectric performance, which hinders their wide applications for the fabrication of high‐performance PENGs.…”

Tunable Magnetism and Insulator–Metal Transition in Bilayer Perovskites

“…Most of the interest was mainly focused on properties related to mechanics under the quantum confinement, leaving their electronic and magnetic properties with definitely similar fundamental scientific importance largely unexplored.Bulk KNbO3 (KNO) and KTaO3 (KTO) perovskites have been studied for over 70 years [17]. The former is famous as room-temperature lead-free ferroelectric material [18], while the latter is so-called incipient ferroelectric [19]. Some exotic properties based on them have been realized by doping, size, dimension or interface engineering, including the magnetic response in nanocrystalline KNO, two-dimensional electron gas…”

“…Bulk KNbO3 (KNO) and KTaO3 (KTO) perovskites have been studied for over 70 years [17]. The former is famous as room-temperature lead-free ferroelectric material [18], while the latter is so-called incipient ferroelectric [19]. Some exotic properties based on them have been realized by doping, size, dimension or interface engineering, including the magnetic response in nanocrystalline KNO, two-dimensional electron gas…”