| Resistive switching devices based on Pt/SrZrO3/SrRuO 3 and Pt/TiO2/Pt heterostructures have been fabricated, tested and characterized. It is shown that the resistance switching in such structures is local, with only a small conducting filament forming within the functional oxide layer. The high power dissipation through the filament core results in significant Joule heating effect during electrical biasing. A local temperature increase exceeding 100°C is observed, using a thermographic imaging technique, at local conduction paths at power levels typical for electroformation and switching. High temperature results in physical changes of the electrode and oxide layer during electroformation and switching. The excessive changes are found to be in part due to excess transient current. By eliminating such excess transient current with new circuitry design, the associated physical damages to the electrodes are eliminated, and the fine structure of the switching filament is analyzed. The oxide layer in the switching filament experiences grain growth, apparently due to Joule heating effect. The originally amorphous TiO2 layer crystallizes into a polycrystalline layer consisting of anatase phase. Simulations of power dissipation in such structures suggest the temperature in the filament during switching is > 320 °C, which is a temperature sufficient for anatase formation. These results suggest that formation of specific conductive secondary phases in TiO2-based devices is not inherent to the switching process, but a by-product of excessive power dissipation. |
