Tuning the analog and digital resistive switching properties of TiO2 by nanocompositing Al-doped ZnO

Resistive switching (RS) is a versatile effect that facilitates the fabrication of non-volatile memory and brain-inspired computing devices by utilizing digital and analog switching. In this work, we demonstrated analog and digital RS properties of titanium dioxide (TiO2) by nanocompositing aluminum-doped zinc oxide (AZO). In particular, we achieved a transition from analog to digital RS by appropriately nanocompositing the AZO (0-25 wt %) in the TiO2 active switching layer. The active switching layers were characterized by different spectroscopic and microscopic techniques, suggested that TiO2 has a tetragonal anatase phase. The morphological study revealed the synthesis of uniform nanocomposite particles. Furthermore, good crystalline nature and phase purities of the nanocomposites were confirmed by HRTEM results. The bare TiO2 possessed rectifying analog RS property whereas, digital RS was observed for 5 to 20 wt % TiO2/AZO-based nanocomposite devices. The digital RS was again converted to analog RS for 25 wt % TiO2/AZO-based device with good hysteresis area and memory window. The time-domain charge and charge-flux characteristics were calculated for all devices, suggesting memristive like properties. The conduction model fitting results suggested that the Schottky and space-charge limited current conduction are responsible for the analog and digital type RS, respectively. Considering the electrical results, we present a possible RS mechanism. The results of the present investigation are useful for the development of non-volatile memory and brain-inspired computing devices.