TUNNELING PERCOLATION MODEL FOR GRANULAR METAL-FILMS

The evolution of conductivity in granular metal films, as a function o f thickness and temperature, has been modeled by percolation within th e framework of the theory of stochastic transport in disordered system s. The model was analytically worked out by means of the effective-med ium approximation. The analytical expression obtained spans the entire range of resistance, from insulating to globally superconducting beha vior, with increasing thickness. Quasireentrant or local superconducti vity was found in our results as a consequence of tunneling junctions allowed in the model. Experimental data on tin films are considered.