Influence of Ti top electrode thickness on the resistive switching properties of forming free and self-rectified TiO2 − x thin films

Abstract

The memory performance of titanium oxide (TiO2−x)-based resistive memories containing an ultra thin reactive Ti top electrode can be greatly enhanced. Very good switching memory characteristics were demonstrated for an Au/Ti/TiO2−x/Au/SiO2/Si structure with the insertion of a Ti nanolayer at the Au/TiO2−x interface. Due to the superb ability of Ti to absorb oxygen atoms from the dielectric matrix, a large amount of oxygen vacancies is created, which are crucial for the stable function of the memory devices. As the Ti thickness increases, a thick interfacial layer is created, which degrades the resistive switching behavior. The induced interface thickness is found also to affect the fluctuation of the ON/OFF processes. The very good switching characteristics which were recorded for the devices containing Ti as top electrode, denote the direct impact that Ti has on the oxygen vacancy density. Oxygen vacancy distribution is also found to be directly associated with the filaments' diameter. Thus, the resistive switching mechanism is proposed to be associated with the formation/rupture of oxygen vacancy-based conducting filaments at the Ti/TiO2−x interface. Self-rectifying characteristics were also recorded for all samples in the low resistance states. Conduction mechanism analysis revealed that trap-assisted-tunneling is the dominant conduction mechanism, which also strongly affects the distribution of the current during SET process.