Low Energy and Analog Memristor Enabled by Regulation of Ru ion Motion for High Precision Neuromorphic Computing

Mobile species and matrix materials in ion motion-mediated memristors predominantly determine the switching characteristics and device performance. As a result of exploring a new type of mobile species, a Ru ion-mediated electrochemical metallization-like memristor with an amorphous oxide matrix is recently suggested to achieve a low switching current, voltage, and good retention simultaneously. Although the ion migration of Ru in the oxide matrix is previously confirmed, no in-depth study on how the crystallinity of the oxide matrix influences the Ru ion motion and switching characteristics has not been reported. Therefore, in this study, the crystallinity-dependent resistive switching behavior of the Pt/HfO₂/Ru structure device is investigated. With the crystallized HfO₂ layer, the preferred Ru ion migration through the grain boundaries occurs owing to the enhanced ion mobility, resulting in a high switching current (≈100 µA) with continuous metallic Ru conducting filaments. The discontinuous conducting filaments with amorphous HfO₂ exhibit a low switching current. In addition, highly linear and symmetric conductance modulation properties are achieved, and over 91.5% accuracy in the Mixed National Institute of Standards and Technology (MNIST) pattern recognition test is demonstrated.