Demonstration of enhanced resistance switching performance of HfO₂/WO_x-based bilayer devices embedded with Ti nano island array by applying a rapid thermal annealing process

In this work, a novel set of methods is prοposed for tuning the oxygen vacancy distribution through the combination of several effects. More specifically, the incorporation of a Ti nano-island (NI), as well as the insertion of a thin layer of HfO₂ with 10 nm thickness and the subsequent enforcement of an annealing step at 400 ℃ are employed to improve the performance of the resistive switching memory devices. The acquired results indicate that the embedded Ti NI array can significantly reduce the switching voltage and the statistical dispersion of the switching characteristics, whereas the increase of both the high resistance state (HRS) and low resistance state (LRS) resistance levels and the reduction of the operating current values are attributed to the existence of the HfO₂ layer. Subsequently, the annealing process under air conditions can effectively reduce the oxygen vacancy content within the device and further improve the R_HRS and on/off ratio. The reduction of the oxygen vacancy concentration is caused by the diffusion of oxygen ions in the air to the dielectric layer during annealing. Hence, it is concluded that the simultaneous incorporation of a Ti NI, a functional layer and a rapid thermal annealing step are regarded as a novel promising and practical technology for significantly improving the whole performance of the memristive elements.