Resistive switches in Ta2O5-α/TaO2−x Bilayer and Ta2O5-α/TaO2−x/TaO2−y Tri-layer Structures

Enough R_off/R_on ratio is important for RRAM application. In this study, a Ta₂O_5-α/TaO_y/TaO_x tri-layer structure device was fabricated by reactive sputtering and plasma oxidation and a Ta₂O_5-α/TaO_x bi-layer structure device was also fabricated for comparison. Resistive switching characteristics of both types of devices were investigated under different compliance current. Both types of devices revealed nearly the same reset current which was as low as ~40 μA. The R_off/R_on ratio of the tri-layer structure devices was increased from 2 to more than 20 by inserting a TaO_y layer. The memory windows of the bi-layer structure devices increased to 3 while the memory windows of the tri-layer structure devices decreased to 8 when the compliance current increased from 40 μA to 60 μA. The stability of the tri-layer structure devices became worse under larger compliance current. The results indicate that that inserting a TaO_y is beneficial for the memory windows of devices and a smaller compliance current is more suitable for the tri-layer structure devices.