Anomalous durability of (001) plane against oxygen vacancy injection at electrode/rutile-TiO[formula omitted] interfaces

Abstract

We have investigated the electro-coloration of a rutile TiO2 single crystal by the voltage-bias annealing in dry air between a point cathode and a flat anode. The electro-coloration is due to the conductive VO filament that grows from the cathode/TiO2 interface to mm size. We proposed that the growth mechanism of this macroscopic size VO filament is the oxygen (O2−) transfer reaction at the anode interface followed by the thermally assisted-electric field-induced VO diffusion to the cathode. It was found that no electro-coloration occurs on (001), whereas it occurs on (110) and (100). This striking contrast between the surface crystal orientations was found to be due to the anisotropic VO diffusion that was found to be much faster perpendicular to [001] than parallel. Accordingly, VO is not injected into the anode/(001) interface in the oxygen transfer reaction. The proposed mechanism was examined by the surface-sensitive TOF-SIMS and the bulk-sensitive dynamic SIMS for analyzing the VO spatial distribution using the 18O isotope tracer. The anomalous durability of the (001) plane against the VO injection suggests that the atomic arrangement of TiO2 at the electrode interface is crucial for controlling the VO filament growth in resistive switching devices.