Electromigration in gold nanowires under AC driving

Abstract

We investigate the relationship between temperature and electron wind force in electromigration (EM) of ultrathin gold nanowires by monitoring power and current density at breakdown under a generalized AC bias (AC with a DC offset). Based on model calculations, our driving frequency of 10 MHz is low enough to maintain steady state self-heating behavior of our wires but high enough that the direction of the wind force switches quickly relative to the time-scale of atomic motion through the junction. The maximum and time-average of the squared current density (which dictate the temperature) both exhibit a minimum in DC offset (which dictates the wind force). This is explained by wind force driven annealing of the wire under long-range atomic displacements. Our hypothesis is supported by observations of changing device resistance on the voltage ramp prior to EM onset and by subsequent SEM inspection of electromigrated devices. The frequency dependence of pure AC EM breaking is also presented and interpreted in terms of the effectiveness of damage healing upon current reversal and the degree of wind force driven annealing.

Feedback Electromigration Assisted by Alternative Voltage Operation for the Fabrication of Facet-Edge Nanogap Electrodes

“…The nanogap with single nanometer scale in width can be reproducibly formed. When we apply iFBEM, because iFBEM has no fixed polarity direction, the nanogap forms near the center between the cathode and anode electrodes . The iFBEM can also reproduce the gap size if the applied voltage and the measurable current are adjusted to the same parameter .…”

“…This indicates that the reconstruction of the Au electrodes was conducted for the four images and suggests that inversing the bias voltage application encourages the Au reconstruction. The Au reconstructions in a vacuum using several application of inversing bias voltages have already been reported . The reconstructed Au nanogap electrodes were automatically achieved by using the iFBEM.…”

“…When we apply iFBEM, because iFBEM has no fixed polarity direction, the nanogap forms near the center between the cathode and anode electrodes. 45 The iFBEM can also reproduce the gap size if the applied voltage and the measurable current are adjusted to the same parameter. 27 After the iFBEM, both the electrodes contain very large grains and sharp facets, implying the crystallization in Au electrodes.…”

“…The Au reconstructions in a vacuum using several application of inversing bias voltages have already been reported. 45 The reconstructed Au nanogap electrodes were automatically achieved by using the iFBEM. Moreover, recrystallization without hydrogen was observed, as shown Figure 4b.…”

Atom Rearrangement by Cyclic Electron “Shaking”

“…[26] The results of previous investigations into the lifetimes of various electronic devices have revealed that the application of an alternating current (AC) or a pulsed current to a material can produce a damage-recovery effect by inducing mechanical stress relaxation during the off-time of the duty cycle. [27][28][29][30][31] These studies focused on preventing electromigration or thermal damage. However, thus far, no reports exist on theoretical or experimental investigations into how manipulation of the atomic arrangement can be realized and how it can improve the material properties.…”