In this study, we investigated the effect of an Al2O3 barrier layer in an all-solid-state inorganic Li-based nano-ionic synaptic transistor (LST) with Li3PO4 electrolyte/WO x channel structure. Near-ideal synaptic behavior in the ultralow conductance range (∼50 nS) was obtained by controlling the abrupt ion migration through the introduction of a sputter-deposited thin (∼3 nm) Al2O3 interfacial layer. A trade-off relationship between the weight update linearity and on/off ratio with varying Al2O3 layer thickness was also observed. To determine the origin of the Al2O3 barrier layer effects, cyclic voltammetry analysis was conducted, and the optimal ionic diffusivity and mobility were found to be key parameters in achieving ideal synaptic behavior. Owing to the controlled ion migration, the retention characteristics were considerably improved by the Al2O3 barrier. Finally, a highly improved pattern recognition accuracy (83.13%) was achieved using the LST with an Al2O3 barrier of optimal thickness.

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Physical unclonable function (PUFs) utilize inherent random physical variations of solid‐state devices and are a core ingredient of hardware security primitives. PUFs promise more robust information security than that provided by the conventional software‐based approaches. While silicon‐ and memristor‐based PUFs are advancing, their reliability and scalability require further improvements. These are currently limited by output fluctuations and associated additional peripherals. Here, highly reliable spintronic PUFs that exploit field‐free spin–orbit‐torque switching in IrMn/CoFeB/Ta/CoFeB structures are demonstrated. It is shown that the stochastic switching polarity of the perpendicular magnetization of the top CoFeB can be achieved by manipulating the exchange bias directions of the bottom IrMn/CoFeB. This serves as an entropy source for the spintronic PUF, which is characterized by high entropy, uniqueness, reconfigurability, and digital output. Furthermore, the device ensures a zero bit‐error‐rate under repetitive operations and robustness against external magnetic fields, and offers scalable and energy‐efficient device implementations.

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