Achieving Long Retention in Area-Dependent Resistive Memory with Phase-Separated Amorphous Tantalum Oxide

Resistive random-access memory (ReRAM) is a promising nonvolatile memory technology. Most ReRAMs exhibit a fundamental tradeoff: filament-type ReRAM provides long data retention but suffers from poor uniformity and high switching current, whereas nonfilamentary ReRAM shows lower-current, area-dependent switching but generally poor retention. No two-terminal device has overcome this tradeoff. We present a two-terminal Ta2O5/ TaOX resistive memory cell that achieves both nonfilamentary switching and long retention. Electrical measurements and composition depth profile show that switching is not confined to a single filament but uniform across the entire switching region. Despite the nonfilamentary switching, this device can retain information for over 22 hours at 190 °C, comparable to the best filamentary devices. We propose that this long retention arises from composition phase separation in amorphous tantalum oxide. Our work shows that the fundamental tradeoff between information retention and switching uniformity can be overcome, providing a pathway toward more uniform and reliable oxide memory devices.