Thermodynamic origin of nonvolatility in resistive memory

Electronic switches based on the migration of high-density point defects, or memristors, are poised to revolutionize post-digital electronics. Despite significant research, key mechanisms for filament formation and oxygen transport remain unresolved, hindering our ability to predict and design device properties. For example, experiments have achieved 10 orders of magnitude longer retention times than predicted by current models. Here, using electrical measurements, scanning probe microscopy, and first-principles calculations on tantalum oxide memristors, we reveal that the formation and stability of conductive filaments crucially depend on the thermodynamic stability of the amorphous oxygen-rich and oxygen-poor compounds, which undergo composition phase separation. Including the previously neglected effects of this amorphous phase separation reconciles unexplained discrepancies in retention and enables predictive design of key performance indicators such as retention stability. This result emphasizes non-ideal thermodynamic interactions as key design criteria in post-digital devices with defect densities substantially exceeding those of today’s covalent semiconductors. [Display omitted] •Uncover an origin of information retention in resistive memory•Explain when and why resistive memory filaments grow or shrink over time•Identify composition phase separation as a mechanism for information storage•Quantify solubility limits in the amorphous tantalum-oxygen system Resistive memory, or a memristor, is a promising technology for future computing applications. One critical property of resistive memory is nonvolatile information retention. Previously, information retention was believed to arise from the slow diffusion of oxygen in the resistive switching material that kinetically “freezes” the information state. In this study, Li et al. show that information retention is not only a result of slow oxygen diffusion but also a thermodynamic property of composition phase separation, whereby there can be several states that are identical in energy. This result not only provides a more accurate physical picture of resistive memory but also highlights phase separation as a new mechanism to enable future information storage devices. Resistive memory is an emerging technology that stores information through a nanosized, oxygen-deficient filament in a transition metal oxide. This work shows that oxygen ions do not follow ideal Fickian diffusion, as commonly believed, but