Bipolar resistive switching with improved memory window in W/ZnFe<inf>2</inf>O<inf>4</inf>/Pt devices

We have demonstrated stable bipolar resistive switching characteristics with low forming voltage in the Rapid Thermal Annealed (RTA) ZnFe2O4 (ZDR6) devices. The structural, surface morphology, surface roughness, and electrical properties of a ZDR6 film was investigated by employing XRD, SEM, AFM and current-voltage (I-V) measurements. The I–V curves show bipolar resistive switching operations. In addition to this, the devices exhibit uniform SET (<1.6 V) and RESET (< -1.1 V) operation with a memory window (MW) larger than two orders of magnitude and show robust retention (>104 s) characteristics. From the physical and electrical characterization, it is inferred that the oxygen vacancies pre-existing in ZDR6 films induced by RTA play the primary role in achieving low forming voltage and later stable SET/RESET operations in these devices. The dominant conduction mechanism in these devices for the high resistance state (HRS) consists of ohmic at a lower bias (< 0.6 V) and space charge limited current at higher bias (> 0.6 V), while for the low resistance state (LRS) they follow the ohmic conduction for the entire range of applied bias. This present work reveals a suitable process to fabricate forming-free resistive switching memory devices.