High-bias breakdown of Au/1,4-benzenedithiol/Au junctions

We have studied the high-bias breakdown of Au/1,4-benzenedithiol (BDT)/Au junctions at room temperature. Exploiting the break junction technique, we held a Au/BDT/Au junction and ruptured it by applying a voltage ramp. The conductance first changes gradually with the bias and then abruptly increases at breakdown. We found that the breakdown voltage shows a broad distribution and takes a maximum at ∼ ( 1.2 - 1.5 ) V . The breakdown voltage is unaffected by the ambient atmosphere but tends to slightly decrease with increasing the junction conductance. We consider that the Au electrode becomes unstable at the breakdown voltage and collapses to crush the junction.