CONDUCTANCE OF ATOMIC-SCALE GOLD CONTACTS UNDER HIGH-BIAS VOLTAGES

The conductance of atomic-scale gold contacts has been studied experim entally as a function of bias voltage. At low voltages, the conductanc e histogram shows a pronounced peak at G(0)=2e(2)/h and broad peaks ne ar 2G(0) and 3G(0). With increasing the bias voltage, these peaks decr ease in height and disappear at some critical voltage, The 1G(0) peak is found to disappear at 1.9 V at room temperature, which corresponds to a critical current of 137 mu A. At liquid-nitrogen temperature, the critical voltage and current slightly increases to 2.2 V and 165 mu A , respectively. The observed disappearance of the conductance peaks ca n be interpreted as a contact instability due to the electromigration of contact atoms induced by a high current density.