A facile solution processible self-rectifying and sub-1 V operating memristor via oxygen vacancy gradient within a TiO₂ single layer

Memristors are becoming increasingly recognized as candidates for neuromorphic devices due to their low power consumption, non-volatile memory, and synaptic properties and the ease of parallel computing through crossbar arrays. However, sneak current is a critical obstacle in crossbar arrays, and much research is being conducted to suppress the sneak current through self-rectifying characteristics. Here, we present a highly straightforward method for fabricating an active layer of a self-rectifying memristor through a single spin coating process, capitalizing on the attributes of spin coating, which initiates the reaction from the upper portion of the solution. We fabricated a self-rectifying memristor using an Ag/TiO₂/TiO_x/ITO structure through a vacuum-free solution process with low cost. During the spin-coating process, the reaction between titanium isopropoxide (TTIP) and ambient moisture formed TiO₂ with an oxygen vacancy gradient. We confirmed the natural oxygen vacancy gradient using X-ray photoelectron spectroscopy (XPS) depth profiling and elucidated the resistance switching and self-rectifying mechanisms of the memristor based on the energy band structure. The memristors exhibited resistance switching and self-rectifying characteristics, which were essential characteristics for preventing sneak currents in a 3 × 3 crossbar array structure.