Alkali Ion-Incorporated HfO2 Dielectrics for Reconfigurable Neuromorphic Computing

Emulating the short- and long-term memory functions of biological synapses in neuromorphic hardware demands dielectric layers whose retention behavior can be precisely and reproducibly tuned. This study reports a solution-processable route to alkali cation-embedded HfO₂ dielectrics that enable programmable synaptic responses in transistor devices. Sodium fluoride (NaF) was blended with electrochemically exfoliated HfS₂ nanosheets prior to thermal oxidation, yielding a uniform, ultrathin (~8 nm) HfO₂ layer with mobile alkali ions dispersed throughout a wafer-scale film. When paired with an IGZO semiconducting channel, transistors built on this dielectric showed markedly different retention behavior depending on composition: devices with unmodified HfO₂ displayed fast, short-lived postsynaptic currents, while those incorporating NaF sustained elevated currents for over 30 seconds and exhibited adjustable synaptic plasticity. Building on this tunability, the ion-engineered dielectric was implemented in several functional circuits, including 1-transistor-1-synapse memory arrays, synaptic comparators, and reconfigurable AND/OR logic gates capable of brain-like signal processing. By broadening the design space for dielectric engineering, this solution-based strategy offers a scalable route toward next-generation neuromorphic devices with finely controllable synaptic characteristics.