Analog and digital resistive switching in W/TiO₂/ITO devices: the impact of crystallinity and Indium diffusion

Abstract

The resistance-switching memristor with capabilities of information storage and brain-inspired computing has prime importance in recent research. In this study, the impact of crystallinity and Indium diffusion on the existence of analog and digital resistive switching in a W/TiO2/ITO device has been reported. The memristor devices are fabricated by depositing titania films by sol–gel and spin-coating techniques. The films annealed at 250 °C and 400 °C were characterized using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The characteristic anatase phase started appearing after annealing at 400 °C, whereas the 250 °C annealed sample was in the amorphous state. The electrical characterization revealed significant differences in the switching characteristics of amorphous and crystalline samples, especially in the switching interface, compliance properties, and current conduction mechanism. The grain boundary assisted oxygen vacancy migration, and the diffusion of indium ions from the ITO bottom electrode helped the crystalline sample to show highly stable and reproducible resistive switching compared to amorphous film. The XPS studies confirmed the indium ion diffusion in the crystalline sample. The oxygen vacancy-induced barrier modulation and conductive filament formation caused characteristic switching in amorphous and crystalline samples, respectively. Schottky emission in the amorphous film and SCLC mechanism in the crystalline film confirmed the experimental results. This study provides a distinctive viewpoint and an innovative strategy for developing multifunctional resistive switching devices.