Schematic illustration of switching mechanism using simple energy band diagrams with I-V characteristics. (a) Energy bands of pristine S1 structure device and ideal leakage current. For TiO2, the solid line is due to the smaller energy gap of the defective TiOx film. I-V of LRS and corresponding energy bands with conducting filaments for (b) S1 and (c) S2 devices. For TaOx, the solid line is due to the lower energy gap caused by the presence of oxygen-deficient filament. The S1 devices show non-ohmic I-V due to TiO2 layer formation at the W/TaOx interface. (d) Filament oxidation and leakage current at HRS are shown for the W/TiOx/TaOx/W devices. Filament formation/rupture is controlled by the TiO2 layer due to O2− ion migration.
Prakash et al. Nanoscale Research Letters 2014 9:125 doi:10.1186/1556-276X-9-125