Atomic Insight into the Origin of Various Operation Voltages of Cation-Based Resistance Switches.

Low operation voltage (VSET), which means low power consumption and good stability, is one of the most important factors in designing the resistance switches with high performance. However, the atomic details for the various VSET values of such devices are still lacking, which hinders their further improvement. In the present study, by taking Ag/Ta2O5/Pt (VSET = 0.6 V) and Cu/Ta2O5/Pt (VSET = 2.0 V) as the examples, we have examined the switching mechanisms of these two cation-based devices by using first principle simulation. Several possible reasons have been addressed to explain the much lower VSET of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt: (i) the faster diffusion of Ag ions in Ta2O5 compared to Cu ions; (ii) the more preferable nucleation process of Ag ions at Pt/Ta2O5 interface compared to Cu ions; (iii) the lower Schottky barrier height (SBH) of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt. On the basis of these results, several key factors have been suggested to design the cation-based resistance switches (oxidizable-metal/Ta2O5/inert-metal) with low VSET values: (i) the weak interaction strength between oxidizable metal ions and Ta2O5 surface; (ii) the low formation energy of oxidizable metal ions on inert electrode; (iii) the low SBH, which could be controlled by tuning the ambient water pressure during the device fabrication process.