Logarithmic temperature dependence of conductivity in a random quasi-two dimensional assembly of gold nanoclusters

Electrical conductivity measurements on a two-dimensional random assembly of Au nanoclusters of an average size 5 nm and an average inter-cluster separation of 12 nm show logarithmic temperature dependence of conductivity in the temperature range 205–229 K followed by an activated nearest neighbour hopping conduction in the temperature range 230–340 K. The activation energy for hopping was found to be approximately equal to the Coulomb charging energy of a cluster. The charge transport between clusters in the logarithmic regime is shown to take place by a random walk of step size equal to the average inter-cluster separation. (paper)