Redox Processes at Interfaces and Ionic Motion in Resistively Switching Materials

The development of modern information technology over the past decades has influenced many aspects of daily life. The progression of this is directly linked to the ongoing miniaturization of electronic devices, such as transistors and Flash memory. As the down-scaling of conventional memory concepts approaches physical limits, novel memory and computation approaches are required. One promising technology for next-generation memories is given by redox based resistive switching random access memories (ReRAM). In ReRAMs the information is stored as programmable electrical resistance state modulated by localized nanoionic transport induced by appropriate voltage stimuli. Redox based resistive switching is observed in several material systems. However, despite many aspects of the underlying physical processes have been understood, several aspects regarding the interplay of materials are still under debate. While resistive switching phenomena can be well explained by cation or anion motion, the influence of specific interfacial redox reactions and incorporation of foreign species on switching/device characteristics are rarely considered.

In this thesis, ReRAMs based on the electrochemical metallization effect (ECM) as well as the valance change memory effect (VCM) are investigated, with special focus on electrochemical processes prior and during the switching process.