On the SET/RESET current asymmetry in electrochemical metallization memory cells

Electrochemical metallization mem-ory (ECM) cells have attracted great attention due to their potential application as Resistive Random Access Memory (ReRAM) in future nonvolatile memories and logic circuits [1–3]. The digital information is encoded as different resist-ance states which can be programmed by applying appro-priate electrical stimuli. ECM cells typically consist of an active silver or copper electrode, an ion conducting switch-ing layer and an inert counter electrode. The switching mechanism in ECM cells relies on the electrochemical growth and dissolution of a copper or silver filament within the switching layer [1]. During SET operation a positive potential is applied to the active electrode and the active silver/copper electrode is oxidized. The correspond-ing cations migrate towards the counter electrode. A reduc-tion occurs at the counter electrode and a silver/copper filament subsequently grows towards the active electrode. As soon as an electronic contact is achieved, e.g. by the onset of electron tunneling between the filament and the active electrode, the resistance drops to the low resistive state (LRS) [4]. By tuning the current limitation during the SET operation different LRS can be programmed accord-ing to the empirical law