Topological disorder and conductance fluctuations in granular thin films

Topological disorder places constraints on the local flow of currents in granular thin films of metals and semiconductors. These constraints in turn influence measurable transport properties such as conductance and conductance fluctuations for these films. This paper quantifies disorder in the disposition of grains within real and simulated thin films by applying methods originally developed studying foam evolution. For simulated Voronoi resistor networks, the overall conductance of a film with a given grain density achieves a minimum value for an intermediate degree disorder. Films of equal of conductances on either side of this minimum can have strikingly different current distributions. The results of simulations of 1/f noise systems in the context of transport and scanning probe microscopy measurement of a-Si:H thin films are discussed.