Conductive metal oxide and hafnium oxide bilayer ReRAM: an ab initio study

TL;DR

This study uses ab initio simulations to analyze bilayer ReRAM devices with conductive metal oxides and hafnium oxide, revealing how filament formation and oxygen content influence resistance states and device stability.

Contribution

It provides new insights into the atomic-scale mechanisms affecting resistance modulation in CMO/HfO2 bilayer ReRAM, highlighting differences between TaO and TiO as conductive layers.

Findings

Filamentary conduction significantly reduces resistance.

Oxygen excess modulates device resistance.

TaO-based devices are more stable with distinct resistance states.

Abstract

We perform generalized gradient approximation (GGA) simulations of interfaces between two Conductive Metal-Oxides (CMO, namely TaO and TiO) and cubic hafnium oxide ($HfO_2$) in the context of bilayer Resistive Random Access Memory (ReRAM) devices. We simulate filamentary conduction in $HfO_2$ by creating an atomically thin O atom vacancy path inside $HfO_2$. We show that this atomically thin filament leads to a great reduction of 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 increas in the resistance when O atoms are inserted inside the CMO. Eventually, we push forward 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 behaviour implying only low and high resistance (two well separated levels) while structures with TiO allows for intermediate resistances.