(Invited) In Situ Transmission Electron Microscopy Analysis of Conductive Filament in Resistance Random Access Memories

In-situ transmission electron microscopy (TEM) analysis of resistance random access memories (ReRAMs) is reported. While ReRAMs have high potentiality as universal memories, there is a big critical issue for making them practicable. It is the obscurity of operation mechanisms. In this report, two typical ReRAM materials, NiO and Cu-GeS, are investigated. It is widely believed that the NiO shows monopolar resistive switching caused by the formation and the breakdown of conducting filaments. On the other hand, a solid electrolyte Cu-GeS shows bipolar switching, where the metallic filament is thought to be formed and dissolved in the material. In order to clarify the operation mechanisms of these ReRAM materials, we employed in-situ TEM direct observation of resistance switching, and succeeded to detect the filament formation for both materials. In addition, the real-time disappearance of the filament in Cu-GeS was clearly recognized in corresponding to the resistance switching.