Spontaneous breaking of nanowires between a STM tip and the Pb(110)surface

We have studied the breaking process of nanowires between a STM tip and the Pb(110) surface, by monitoring the conductance of the connection throughout the process. Connecting necks form spontaneously when the tip is brought close to the Pb surface. Surprisingly, the necks break spontaneously after they have been stretched to a certain degree by tip retraction. The dependence of the breaking behavior on temperature and surface contamination suggests that the process is caused by surface diffusion. Comparison of the experiment with model calculations provides further evidence that capillarity-induced surface diffusion is responsible for the process. From the difference between the rates of evolution of the neck at two different temperatures the apparent activation energy for the process has been determined to be 0.53 eV.