Improvement on synaptic properties of WO x -based memristor by doping Ti into WO x

Abstract Doping Ti into WO x is widely used to improve the performance of various WO x -based devices. However, Ti-doped WO x (Ti:WO x ) based memristors have not been investigated in depth, especially regarding their synaptic properties. In this report, Ti:WO x films are deposited by sputtering WTi alloy target in Ar + O 2 atmosphere, in which the substrates are not heated, avoiding the precipitation of TiO 2 phase. As-grown Ti:WO x films exhibit polymorphous crystallized structures, originating from the topological deformation of WO 6 octahedron by replacing W with Ti. Furthermore, the memristor with the structure of W/Ti:WO x / indium-doped tin oxide demonstrates typical synaptic properties, including the controllable synapse weight update by adjusting the input pulse amplitude, interval, as well as the transformation from the paired-pulse facilitation to the paired-pulse depression. Moreover, the higher Ti–O band energy leads to smaller hysteresis loop areas of its current–voltage ( I – V ) curves, which may mean better synaptic performances, such as higher resolution. Additionally, contrary to other metal-oxide based memristors, our device conductance increases by applying positive voltage scans or a series of positive pulses on the metal electrode. Otherwise, it will decrease. With I – V fitting and the energy-band diagrams, we analyzed deep carrier transport processes, revealing a unique synaptic mechanism.