Bipolar resistive switching in transparent AZO/SiOx/ITO devices

Transparent resistive random access memory (RRAM) devices comprising an aluminum-doped zinc oxide (AZO) top electrode and a silicon oxide (SiO x ) resistor layer were fabricated on top of an indium–tin oxide (ITO) glass substrate by sputter deposition. The average transmittance of the AZO/SiO x /ITO-glass structure was 85% in the visible range. The RRAM devices exhibited bipolar switching of resistance after a forming procedure at +7.2 V, and the devices could be switched 100 times between the high resistance state and the low resistance state with resistance ratios greater than 16. The area- and temperature-dependent resistances of the RRAM devices suggested that electrical conduction was realized via the filamentary path inside the SiO x layer. Incorporation of Zn, Al, In, and Sn into the SiO x layer facilitated the formation of metallic filaments. Migration of oxygen ions near the AZO/SiO x interface might induce rupture and connection of the filaments as well as resistance switching in AZO/SiO x /ITO devices.