Structural Properties and Thermodynamics of Hafnium sub-oxides in RRAM

We study the structural and electronic properties of various hafnium sub-oxides HfzO from z = 9 to z = 0.5, by ab initio simulation using Density Functional Theory. The stability of these sub-oxides is studied against monoclinic HfO2. The progressive oxidation of a given HfzO is also envisaged toward stoichiometric HfO2. The analogy with a conductive region of electrons inside a HfO2 matrix is discussed within the context of Oxide-based Resistive Random Access Memories (OxRRAM) devices which employ hafnium dioxide as an insulator.