  Current-voltage characteristics in the insulator bordering superconductivity
in disordered thin films exhibit current jumps of several orders of magnitude
due to the development of a thermally bistable electronic state at very low
temperatures. In this high-resolution study we find that the jumps can be
composed of many (up to 100) smaller jumps that appear to be random. This
indicates that inhomogeneity develops near the transition to the insulator and
that the current breakdown proceed via percolative paths spanning from one
electrode to the other.
