A study on the resistance switching of Ag ₂ Se and Ta ₂ O ₅ heterojunctions using structural engineering

The resistive random access memory (RRAM) devices with heterostuctures have been investigated due to cycling stability, nonlinear switching, complementary resistive switching and self-compliance. The heterostructured devices can modulate the resistive switching (RS) behavior appropriately by bilayer structure with a variety of materials. In this study, the bipolar resistive switching characteristics of the bilayer structures composed of Ta 2 O 5 and Ag 2 Se, which are transition-metal oxide (TMO) and silver chalcogenide, were investigated. The bilayer devices of Ta 2 O 5 deposited on Ag 2 Se (Ta 2 O 5 /Ag 2 Se) and Ag 2 Se deposited on Ta 2 O 5 (Ag 2 Se/Ta 2 O 5 ) were fabricated for investigation of the RS characteristics by stacking sequence of Ta 2 O 5 and Ag 2 Se. All operating voltages were applied to the Ag top electrode with the Pt bottom electrode grounded. The Ta 2 O 5 /Ag 2 Se device showed that a negative voltage sweep switched the device from high resistance state (HRS) to low resistance state (LRS) and a positive voltage sweep switched the device from LRS to HRS. On the contrary, for the Ag 2 Se/Ta 2 O 5 device a positive voltage sweep switched the device from HRS to LRS, and a negative voltage sweep switched it from LRS to HRS. The polarity dependence of RS was attributed to the stacking sequence of Ta 2 O 5 and Ag 2 Se. In addition, the combined heterostructured device of both bilayer stacks, Ta 2 O 5 /Ag 2 Se and Ag 2 Se/Ta 2 O 5 , exhibited the complementary switching characteristics. By using threshold switching devices, sneak path leakage can be reduced without additional selectors. The bilayer heterostructures of Ta 2 O 5 and Ag 2 Se have various advantages such as self-compliance, reproducibility and forming-free stable RS. It confirms the possible applications of TMO and silver chalcogenide heterostructures in RRAM.