Adaptive Crystallite Kinetics in Homogenous Bilayer Oxide Memristor for Emulating Diverse Synaptic Plasticity

A critical routine for memristors applied to neuromorphic computing is to approximate synaptic dynamic behaviors as closely as possible. A type of homogenous bilayer memristor with a structure of W/HfOy/HfOx/Pt is designed and constructed in this paper. The memristor replicates the structure and oxygen vacancy (VO) distribution of a complete synapse and its Ca2+ distribution, respectively, after the forming process. The detailed characterizations of its atomic structure and phase transformation in and near the conductive channel demonstrate that the crystallite kinetics are adaptively coupled with the VO migration prompted by directional external bias. The extrusion (injection) of the VOs and the subsequent crystallite coalescence (separation), phase transformation, and alignment (misalignment) resemble closely the Ca2+ flux and neurotransmitter dynamics in chemical synapses. Such adaptation and similarity allow the memristor to emulate diverse synaptic plasticity. This study supplies a kinetic process of conductive channel theory for bilayer memristors. In addition, our memristor has very low energy consumption (5–7.5 fJ per switching for a 0.5 µm diameter device, compatible with a synaptic event) and is therefore suitable for large‐scale integration used in neuromorphic networks. A homogenous bilayer memristor replicates structure and oxygen vacancy (VO) distribution of a complete synapse and Ca2+ distribution, respectively. Crystallite kinetics are adaptively coupled with the VO migration, including crystallite coalescence, phase transformation, and alignment, which resemble closely the Ca2+ flux and neurotransmitter dynamics in chemical synapses. Such adaptation and similarity permits emulating diverse synaptic plasticity.