Monte Carlo simulation of mixed multilayer adsorption: layering transitions and wetting phenomena in non-ideal mixtures

The formation of two-component multilayer films on solid surfaces in the sy stems of adsorbates, which exhibit positive deviations from ideal mixing, i s studied using a Monte Carlo simulation method. Phase behaviour of the sys tems exhibiting complete and incomplete wetting at the ground state is disc ussed. Phase diagrams for several systems are determined. It is demonstrate d that the systems studied exhibit strong effects of enhanced adsorption of one component due to adsorption of the second component. It is also shown that the presence of preadsorbed particles of one component may considerabl y change the surface wetting by the second component. In particular, it is demonstrated that the addition of strongly adsorbed particles into the syst em may lead to the cross-over from the intermediate to the strong substrate regime. On the other hand, in the systems considered here the wetting temp erature appears to be practically unaffected by the second component. When the wetting transition is preceded by the (first-order) prewetting transiti on, its critical point, is shifted towards higher temperatures due to the e nhancement of adsorbate-adsorbate interaction resulting from the enhanced a dsorption of the second component. (C) 2000 Elsevier Science B.V. All right s reserved.