Adsorption thermodynamics of cross-shaped molecules with one attractive arm on random heterogeneous square lattice

Abstract

Understanding the forces governing the arrangement of organic molecules on the solid surface is the key to control and creation of self-assembled organic nanostructures. In this paper we use the simple lattice gas model and grand canonical Monte Carlo method to demonstrate how the random surface heterogeneity affects both structural and thermodynamic properties of the adsorption overlayer of cross-shaped molecules with one attractive arm. The simulated results show that phase behavior of the adlayer on the random heterogeneous surface characterized by small energy difference between adsorption on the “weak” and “strong” sites and/or low concentration of the “strong” sites (0.1 and less) can be described as the hierarchical self-assembly process. On the other hand, the simulations performed for the system with large energy difference between adsorption on the “weak” and “strong” sites revealed that the stable phases appearing on the surface at coverage close to 0.5 and higher are the balance products of the “adsorbate–adsorbate” and “adsorbate–substrate” interactions.