10:45 AM - 11:00 AM
[16a-419-7] Observation of Filamentary Conducting Channels in Resistive Switching Operation Using Atomically Flat Films of a-TaOx
Keywords:resistive switching memory, ReRAM, tantalum oxide
Increasing attention has been paid to defect migration in metal oxides because of its potential application to resistive random access memory (ReRAM), which is known as one of the most promising candidate device for next-generation nonvolatile memory. The accepted mechanism of oxide-based resistive switching is based on formation and rupture of filamentary conducting channels by field-driven migration of oxygen defects. Owing to the predicted important role, many recent works have been done to observe the nanoscale conductive filaments by microscopic methods. However, the reported studies have revealed that formation of conductive channels is critically influenced by sample structure and the observation of filamentary channels is easily hindered by structural inhomogeneity including surface roughness and grain boundaries.
To address this issue, we developed atomically flat thin films of amorphous TaOx (a-TaOx), which is known as a typical resistive switching material with good memory characteristics, by pulsed laser deposition method. We performed conductive AFM analysis for the developed a-TaOx films and observed clear hysteretic behavior in the current-voltage characteristics at any point on the surface. This confirmed the advantage of the atomically flat a-TaOx for SPM investigation of resistive switching. By applying a voltage of +2.5 V from an AFM prove, the film was turned into the low-resistive state, and deformation with a small height of ~0.5 nm and a relatively large area of ~50 nm was observed on the surface around the tip points. We achieved the observation of a single conducting filament with ~10 nm size at the center of deformation in the current image. In addition, our experiments revealed that the formation of a conducting filament is accompanied by an increase in the resistance of the surrounding TaOx film. This result suggested the occurene of lateral migration of oxygen defects around the filament and its important role in resistive switching.
To address this issue, we developed atomically flat thin films of amorphous TaOx (a-TaOx), which is known as a typical resistive switching material with good memory characteristics, by pulsed laser deposition method. We performed conductive AFM analysis for the developed a-TaOx films and observed clear hysteretic behavior in the current-voltage characteristics at any point on the surface. This confirmed the advantage of the atomically flat a-TaOx for SPM investigation of resistive switching. By applying a voltage of +2.5 V from an AFM prove, the film was turned into the low-resistive state, and deformation with a small height of ~0.5 nm and a relatively large area of ~50 nm was observed on the surface around the tip points. We achieved the observation of a single conducting filament with ~10 nm size at the center of deformation in the current image. In addition, our experiments revealed that the formation of a conducting filament is accompanied by an increase in the resistance of the surrounding TaOx film. This result suggested the occurene of lateral migration of oxygen defects around the filament and its important role in resistive switching.