Understanding the role of Interface and Bulk Conduction in the PCMO RRAM

Pr1-xCaxMnO3 (PCMO) Resistance Random Access Memory (RRAM) has attracted widespread attention in large scale neuromorphic applications as it is non-filamentary, area scalable and has multiple resistance states along with excellent endurance and retention. The PCMO RRAM shows exhibit resistive switching when in contact with an oxidizable electrode. Many studies have been done to demonstrate the existence of an oxygen-deficient interface or oxygen-deficient bulk region as the cause of resistive switching. However, most of the electrical characterization based studies have the interference of the oxidizable electrode and film interface in its path. This interference makes it difficult to clearly understand the exact mechanism i.e. oxygen deficient interface or bulk region of PCMO. To have a clear understanding of the conduction mechanism in the PCMO RRAM, it is essential to avoid the interference of the oxidizable electrode in the electrical characterization. In this paper, we propose and experimentally demonstrate a novel three-terminal RRAM device in which a thin third terminal surrounds (~20nm) the middle of a typical 2 terminal RRAM device (~80nm) and is isolated from both of the RRAM electrodes. From this structure, we successfully isolate the interface and bulk conduction paths and show that not only the interface but the oxygen-deficient bulk region is also responsible for the resistive switching in the PCMO RRAM. Such a study enables a critical understanding of the device which enables the design and development of PCMO RRAM for memory and neuromorphic computing applications.