Oxygen-Plasma-Treated Al/TaO_X/Al Resistive Memory for Enhanced Synaptic Characteristics

In this study, we investigate the impact of O₂ plasma treatment on the performance of Al/TaO_X/Al-based resistive random-access memory (RRAM) devices, focusing on applications in neuromorphic systems. Comparative analysis using scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the differences in chemical composition between O₂-plasma-treated and untreated RRAM cells. Direct-current measurements showed that O₂-plasma-treated RRAM cells exhibited significant improvements over untreated RRAM cells, including higher on/off ratios, improved uniformity and distribution, longer retention times, and enhanced durability. The conduction mechanism is investigated by current–voltage (I–V) curve fitting. In addition, paired-pulse facilitation (PPF) is observed using partial short-term memory. Furthermore, 3- and 4-bit weight tuning with auto-pulse-tuning algorithms was achieved to improve the controllability of the synapse weight for the neuromorphic system, maintaining retention times exceeding 10³ s in the multiple states. Neuromorphic simulation with an MNIST dataset is conducted to evaluate the synaptic device.