MoS₂/HfO₂ Heterostructure Interface Engineering for Stable and Reproducible Resistive Switching in Ag/HfO₂/TiN Memristors for Intelligent Sensor Nodes

Resistive switching devices are attractive candidates for nonvolatile memory and sensory information storage in intelligent sensor nodes, but their use near sensors remains limited by switching variability and resistance state instability. In this work, a two-dimensional MoS₂ interlayer is introduced into an Ag/HfO₂/TiN memristor stack to form a MoS₂/HfO₂ heterostructure device, and its electrical characteristics are compared with an Ag/HfO₂/TiN control device fabricated under the same oxide deposition and annealing conditions. The heterostructure device exhibits well-defined and reproducible bipolar resistive switching with an on/off ratio of up to approximately 10³, together with markedly improved cycle-to-cycle overlap of the current-voltage characteristics, whereas the switching window of the control device narrows and eventually closes after repeated sweeps. X-ray photoelectron spectroscopy of the O 1s core level shows that the oxygen-vacancy-related component decreases from 18.31% to 5.12% of the fitted spectral envelope after introduction of the MoS₂ interlayer, while the lattice-oxygen component remains essentially unchanged. This selective reduction is attributed to interfacial passivation of electrically active vacancies rather than to bulk oxygen extraction, and it cannot be explained by signal attenuation of the buried oxide under the MoS₂ overlayer. Retention measurements show that the heterostructure device maintains stable high- and low-resistance states over the measured 10³ s window, while the high-resistance state of the control device decays by orders of magnitude within the same period. The switching polarity, the correlation between vacancy chemistry and switching uniformity, and the stability of the ruptured-filament state are consistent with an interface-guided valence-change mechanism, although a minor contribution of Ag-ion migration cannot be excluded. These results indicate that MoS₂/HfO₂ heterojunction engineering is an effective route toward mitigating variability and retention degradation in oxide-based memristors for intelligent sensing hardware. The measured resistance window, repeatable switching, and state retention are relevant to local storage of sensor features, calibration coefficients, and adaptive thresholds in robotic perception. The present work establishes the memory component of such sensor nodes and does not claim direct transduction or a complete robotic sensing system.