Making reversible transformation from electronic to ionic resistive switching possible by applied electric field in an asymmetrical Al/TiO2/FTO nanostructure

[Display omitted] •The asymmetrical Al/TiO2/FTO sandwiched nanostructure is prepared and characterized.•The reversible transformation between eRS and the iRS operating mode is realized by applied electric field.•A possible mechanism for transformation between eRS and iRS operating mode is proposed. Here, the design and fabrication of an asymmetrical Al/TiO2/FTO sandwiched nanostructure is reported by using simple spin-coating and vacuum deposition techniques. This intentionally designed asymmetrical sandwiched nanostructure is suited for nonvolatile memristor that the electronic resistive switching (eRS) and the ionic resistive switching (iRS) can coexist and reversibly transform each other. The coexistence and reversible transformation could be induced and controlled by applied electric field, which means that there is a critical electric field for transformation of two operating modes. That is when the applied electric field is smaller than the critical electric field, the oxygen vacancies cannot form a conductive filament, instead it acts as a trap centers, and the Al/TiO2/FTO memristor presents the eRS operating mode by trapping and detrapping of carriers. Conversely, when the applied electric field is greater than the critical electric field, the electric field induces oxygen vacancies to migrate, and then the Al/TiO2/FTO memristor presents the iRS operating mode by the formation and rupture of the conductive filaments. For that, we have also discussed the corresponding transformation mechanism for the two modes of resistive switching in detail.