Multilevel Resistive Switching Dynamics by Controlling Phase and Self-Assembled Nanochannels in HfO₂

A resistive switching device with precise control over the formation of conductive filaments (CF) holds immense potential for high-density memory arrays and atomic-scale in-memory computing architectures. While ion migration and electrochemical switching mechanisms are well understood, controlling the evolution of CF remains challenging for practical resistive random-access memory (RRAM) deployment. This study introduces a systematic approach to modulate oxygen vacancies (OV) in HfO₂ films of Ag/HfO₂/Pt-based RRAM devices by controlling the substrate temperature. At 300 °C, the HfO₂ film exhibits a dominant monoclinic phase with maximum OV concentration, which plays a key role in achieving optimal multilevel resistive switching behavior. Self-assembled nanochannels in the HfO₂ films guide CF evolution, and the diffusion of Ag at inside these films suggests a synergistic interplay between OV and Ag⁺ ion migration for reseting the voltage-controlled resistive states. This approach addresses the endurance/retention trade-off with an impressive R_on/R_off ratio of ≈8000 while demonstrating growth temperature-driven OV modulation as a tool for multi-bit data storage. These findings provide a blueprint for developing high-performance oxide-based RRAM devices and offer valuable insights into multilevel resistive switching mechanisms, paving the way for future low-power, high-density memory technologies.