The conductance of atomic-scale gold contacts has been studied experimentally as a function of bias voltage. At low voltages, the conductance histogram shows a pronounced peak at $G_0{=2e}^2/h$ and broad peaks near 2$G_0$ and 3$G_0.$ With increasing the bias voltage, these peaks decrease in height and disappear at some critical voltage. The 1$G_0$ peak is found to disappear at 1.9 V at room temperature, which corresponds to a critical current of 137 μA. At liquid-nitrogen temperature, the critical voltage and current slightly increases to 2.2 V and 165 μA, respectively. The observed disappearance of the conductance peaks can be interpreted as a contact instability due to the electromigration of contact atoms induced by a high current density.

• Received 21 March 1997

DOI:https://doi.org/10.1103/PhysRevB.56.1069