The effect of the top electrode on the switching behavior of bipolar Al2O3/ZnO RRAM

In this letter, the atomic layer deposited (ALD) resistive random access memory(RRAM) device with Au/Al2O3/ ZnO/FTO structure (ox-RRAM) exhibiting bipolar characteristics is proposed to compare with Ag/Al2O3/ZnO/ FTO (conduction bridge RRAM(CBRAM)) device to demonstrate the effect of electrode material on device behavior. Although both devices have undergone similar processes during the fabrication, the proposed device with Au top electrode shows oxygen vacancy-based valance change mechanism (VCM) of switching with two stable states. The latter follows conductive metallic bridge-based switching (CBRAM) with multilevel storage. However, both devices have shown self-compliance feature, with a maximum current settled to 10-20 mA. Also, they have distinguishable memory window (Roff/Ron) > 102. The current conduction mechanism in both devices follows ohmic conduction and space charge limited conduction (SCLC) at low resistance state (LRS) and high resistance state (HRS), respectively. It reveals that the stacking of oxide layers and deposition method influence the electronic conduction mechanism, whereas the top electrode has a prominent role in the switching mechanism. It is also reported that the endurance and retention of the proposed ox-RRAM are better than its CBRAM counterpart.