Conductive metal oxide and hafnium oxide bilayer resistive random-access memory: An ab initio study

We perform density functional theory simulations of interfaces between two conductive metal-oxides (CMOs, namely, TaO and TiO) and cubic hafnium oxide (HfO2) in the context of bilayer Resistive Random Access Memory devices. These simulations are made at the generalized gradient approximation level. We simulate filamentary conduction in HfO2 by creating an atomically thin O atom vacancy path inside HfO2. We show that this atomically thin filament leads to a great reduction in the resistance of the structures. Moreover, we explore the possibility of the influence of O excess inside the CMO on the global resistance of the device and confirm the induced modulation. We also shed the light on two possible causes for the observed increase in the resistance when O atoms are inserted inside the CMO. Eventually, we push forward the key differences between devices with TaO and TiO as CMO. We show that structures with TaO are more stable in general and lead to a behavior implying only low and high resistance (two well-separated levels) while structures with TiO allow for intermediate resistances.