The dependence of bottom electrode materials on resistive switching characteristics for HfO 2 /TiO x bilayer structure RRAM

In this paper, we systematically investigated the dependence of three types of bottom electrode (BE) materials, such as active Cu and Ag, inert Pt and Au, and oxygen-affinity W and Ti, on resistive switching characteristics for HfO 2 /TiO x bilayer structure RRAM devices with Pt served as the same top electrode (TE). It is found that the RRAM devices with oxygen-affinity BE (W or Ti) can significantly improve the fluctuations of main switching parameters compared to the other two types of BE. Moreover, the Reset processes in RRAM devices with oxygen-affinity BE exhibit gradual transition, which can be used to obtain multilevel storage capability. Thus, a reliable 2-Bit storage operation can be successfully obtain in Ti BE/HfO 2 /TiO x /Pt TE RRAM device by controlling the Reset-stop voltage. These results provide insights into the proper selection of oxide-based switching layer and electrode materials to improve the performance of the related RRAM devices.