Improved performance of ITO/TiO2/HfO2/Pt random resistive accessory memory by nitrogen annealing treatment.

Resistive switching (RS) characteristics of TiO2/HfO2 bilayer memory devices annealed under N2 and O2 ambient were investigated in this work. It was found that the improved RS properties were obtained in N2 annealing atmosphere, which exhibited good endurance of more than 100 times in direct current measurement mode and data retention properties of 104s at 85°C. To clarify the effect of annealing treatment on the devices in various atmospheres, conduction mechanism, which is related to the RS properties was analyzed. The results showed that the space charge limited current (SCLC) was the dominant conduction mechanism in HRS for the as prepared device; for the device annealed in N2, the conduction mechanism was dominated by Pool–Frenkel emission. It can be induced that the conduction mechanism variation in N2 was attributed to the increase of oxygen vacancies in the switching layer, which was the main reason for the improvement of RS characteristics. Lastly, we switched the operation voltage from the Pt to the ITO electrode of the double layer RRAMs, and found that better endurance and smaller operation voltages were obtained when it was applied on the Pt electrode.