Nonvolatile Electrochemical Random-Access Memory Enabled by Phase Separation

Electrochemical random access memory (ECRAM) is a promising recently developed device for analog computing. Like resistive random access memory (RRAM), ECRAM also stores and switches information through ion migration and the resulting change in valence and electronic conductivity. ECRAM is a three-terminal memory cell that electrochemically shuttles oxygen vacancy point defects between two transition metal oxides with a solid electrolyte sandwich. ECRAM enables analog, continuous retention state switching (~100 states) by deterministically modulating oxygen vacancy concentration. In the past, ECRAM suffered from poor retention, about several hours at room temperature and several minutes at 85C, substantially less than &gt;10 years at 85C standard for most nonvolatile memory.<br/><br/>In this work, we utilize new materials that not only meet, but vastly exceed the 10 year retention time metric. We hypothesize that the poor retention in the previous ECRAM results from using solid solution materials; in contrast, our phase separating materials enable multiple equilibrium states and thereby substantially improve e retention in ECRAM. Moreover, our results show that a nonvolatile ECRAM with a retention time more than 12 hours at 400C, exceeds the performance of the best nonvolatile memory cell. Our work shows that harnessing phase separation can provide a powerful means to enable nonvolatile ECRAM to attain the necessary retention times and ECRAM’s ability to electrochemically move point defects within solids for both analog and high-temperature memory.