Filamentary Resistive Switching in an SrTiO₃/TiO₂ Heterostructured Nanotube Array

Abstract

In the current study, the resistive switching phenomenon was measured in an SrTiO 3 /TiO 2 heterostructured nanotube array. A highly aligned TiO 2 nanotube array was grown by the anodic oxidation method and an SrTiO 3 layer was grown by hydrothermal treatment of the TiO 2 nanotubes in an Sr(OH) 2 precursor of different molarities varying from 0.25 to 25 mM. The morphology and defect density of the nanotubes were altered significantly due the growth of SrTiO 3 on the TiO 2 nanotubes. The morphology, structure, crystallinity, defects distribution etc. of the SrTiO 3 /TiO 2 heterostructured nanotube array were extensively characterized in the current study. The line profile measurement by energy dispersive spectroscopy envisaged the gradual decrease of the growth of SrTiO 3 from the top to the bottom of the nanotube. The Au/SrTiO 3 −TiO 2 heterostructured nanotube/Ti devices were tested for the resistive switching study and electroforming free filamentary-type switching was observed. The SrTiO 3 /TiO 2 heterostructured nanotube synthesized with the 2.5 mM precursor was considered as the best-performing material, exhibiting an R OFF /R ON ratio of ∼12 (read voltage: 0.5 V) with excellent retention (10 6 s) and endurance characteristics. The overall switching study was carried out at below ±2 V. The resistive switching mechanism was explained with a conducting filament formation/rapture model, which was implemented on an individual nanotube and eventually established the multiple-filament approach. The SrTiO 3 /TiO 2 heterojunction also played a significant role by modulating the transport barrier under SET and RESET operations.