Temperature effects on the switching kinetics of a Cu-Ta2O5-based atomic switch

Voltage-current (I-V) measurements in a wide temperature range from 88 to 573 K demonstrated the effects of temperature on the switching behavior of a Cu/Ta(2)O(5)/Pt resistive memory cell that is referred to as a gapless-type atomic switch. After the forming process, the cells were SET from the OFF state to the ON state at a positive bias to the Cu electrode and then RESET from the ON state to the OFF state at a negative bias. In a previous study (Tsuruoka et al 2010 Nanotechnology 21 425205), it was demonstrated that the SET process corresponds to the reformation of a metal filament between the electrodes by the inhomogeneous nucleation and subsequent growth of Cu whereas the RESET process can be attributed to the Joule-heating-assisted dissolution of the metal filament. In the work described here, we observed that the voltages at which the cells are SET and RESET (SET and RESET voltages) decreased in magnitude with an increase in temperature. From calculations of the nucleation rate of Cu nuclei based on the classical nucleation theory, it was found that the observed temperature variation of the SET voltage is primarily determined by supersaturation in the vicinity of the Pt electrode, which is controlled by the application of positive bias. The supersaturation required for spontaneous growth of a Cu nucleus decreases with increasing temperature, resulting in lower SET voltages at higher temperatures. The RESET voltage is determined by the thermal stability of the metal filament formed. Moreover, using the temperature variation in cell resistances of the ON state, the growth speed of the Cu nucleus after the nucleation was found to decease with increasing temperature. These results are consistent with our switching model.