Sol-gel synthesis and nonvolatile resistive switching behaviors of the wurtzite phase ZnO nanofilms

A facile sol-gel method and heating treatment process have been reported to synthesize the wurtzite phase ZnO nanofilms with the preferential growth orientation along the [001] direction on the FTO substrates. The as-prepared wurtzite phase ZnO nanofilms-based memristor with the W/ZnO/FTO sandwich has demonstrated a reliable nonvolatile bipolar resistive switching behaviors with an ultralow set voltage of about +3 V and reset voltage of approximately -3.6 V, high resistive switching ratio of more than two orders of magnitude, good resistance retention ability (up to 104 seconds), and excellent durability. Furthermore, the resistive switching behavior in the low-resistance state is attributed to the Ohmic conduction mechanism, while the resistive switching behavior in the high-resistance state is controlled by the trap-modulated space charge limited current (SCLC) mechanism. In addition, the conductive filament model regulated by the oxygen vacancies is proposed, where the absence of nonvolatile memory behavior can be attributed to the formation and rupture of conductive filaments in the W/ZnO/FTO memristor. This work demonstrates that the as-prepared wurtzite phase ZnO nanofilms-based W/ZnO/FTO memristor has promising prospects in future nonvolatile memory applications.