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Solution-processed silver sulphide nanocrystal film for resistive switching memories

Resistive switching memories allow electrical control of the conductivity of a material, by inducing a high resistance (OFF) or a low resistance (ON) state, using electrochemical and ion transport processes. As alternative to high temperature and vacuum-based physical sulphurization methods of silver (Ag), here we propose, as resistive switching medium, a layer built from colloidal Ag$_{2-x}$S nanocrystals -compatible with solution-processed approaches. The effect of the electrode size (from macro- to micro-scale), composition (Ag, Ti and Pt) and geometry on the device performance together with the electrochemical mechanisms involved are evaluated. We achieved an optimized Ag/Ti bowtie proof-of-concept configuration by e-beam lithography, which fulfils the general requirements for ReRAM devices in terms of low power consumption and reliable $I_{ON}/I_{OFF}$ ratio. This configuration demonstrates reproducible switching between ON and OFF states with data endurance of at least 20 cycles; and an $I_{ON}/I_{OFF}$ ratio up to 10$^3$ at low power consumption (0.1V readout), which outperforms previous results in literature for devices with resistive layers fabricated from silver chalcogenide nanoparticles.