  We report unexpectedly large noise in the current from nanopatterned PbS
quantum dot films. The noise is proportional to the current when the latter is
varied by changing the source-drain bias, gate voltage or temperature. The
spectral density of the noise is given by a power law in frequency at room
temperature, but remarkably, we observe a transition to telegraph noise at
lower temperatures. The probability distribution of the off-times follows a
power law, reminiscent of fluorescence blinking in colloidal quantum dot
systems. Our results are understood simply in terms of conductance fluctuations
in a quasi-one dimensional percolation path, and more rigorously in terms of a
model in which charge through the film is transmitted in discrete time
intervals, with the distribution of intervals completely described by Levy
statistics.
