Oxygen-modulated quantum conductance for ultrathin HfO2 -based memristive switching devices

Memristive switching devices, candidates for resistive random access memory technology, have been shown to switch off through a progression of states with quantized conductance and subsequent noninteger conductance (in terms of conductance quantum ${G}₀)$. We have performed calculations based on density functional theory to model the switching process for a $\mathrm{Pt}\text{\ensuremath{-}}{\mathrm{HfO}}₂$-Pt structure, involving the movement of one or two oxygen atoms. Oxygen atoms moving within a conductive oxygen vacancy filament act as tunneling barriers, and partition the filament into weakly coupled quantum wells. We show that the low-bias conductance decreases exponentially when one oxygen atom moves away from interface. Our results demonstrate the high sensitivity of the device conductance to the position of oxygen atoms.