Monte Carlo simulation study of the thicknesses of wetting layers in pure and impure (quenched random-field) environments

Wetting layer thicknesses have been measured in Monte Carlo simulations of a three-dimensional solid-on-solid model of adsorption. In a pure environment the average thickness l is found to follow the expected logarithmic law as a function of the undersaturation or bulk field hB. At small hB the results are consistent with a cross-over to a power law l ∞ h-1B, predicted on the basis of finite-size effects. In an impure quenched random-field environment a logarithmic law is found at relatively large hB, as for the pure system. When hB is lowered the simulations show pinning of the interface by the random fields, implying slowing down of the relaxation, strong dependence on the starting configuration, and strong sensitivity to the random-field environment. In addition to the cross-over due to the finite system size, these problems have made the expected power-law behaviour l ∝ h-12B inextricable.