Abstract
To study the metal-insulator transitions in granular systems, we propose a microscopic model, which contains two terms, the first term represents the charging energy, and the second is quantum tunneling. We performed Monte Carlo simulations in this model, and find the phase diagrams of granular films with different metal volume fractions. The phase diagrams of granular films demonstrate that random disorder make the granular systems more insulating. This is because disorder increases the effect of Coulomb interaction and the difficulty of quantum tunneling of elections between metal granules.