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 (SiOx) resistor layer were fabricated on top of an indium-tin oxide (ITO) glass substrate by sputter deposition. The average transmittance of the AZO/SiOx/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 SiOx layer. Incorporation of Zn, Al, In, and Sn into the SiOx layer facilitated the formation of metallic filaments. Migration of oxygen ions near the AZO/SiOx interface might induce rupture and connection of the filaments as well as resistance switching in AZO/SiOx/ITO devices.