Modelling of the particle size distribution function in the nucleation and early stages of thin film growth

The nucleation and early stages of thin film growth on solid surfaces has been modelled through the rate equation approach at submonolayer coverages. The formation of stable clusters implies adsorption, nucleation and growth processes to occur at the substrate surface. The closure of the system of differential equations is achieved using the growth law of the nucleus. The kinetics, solved numerically, gives the time dependence of the surface coverages of free-monomers, unstable and stable clusters. The particle size distribution function is eventually obtained by the nucleation kinetics through the microscopic growth law of the islands. Preliminary results, at room temperature, are reported for the cases of two dimensional stable dimers and trimers in the total condensation regime. At a given value of the maximum surface coverage the effect of the monomer flux at the substrate surface, on the particle size distribution function, has been also studied. Experimental data on the Pt deposition at the Al2O3NiAl(110) substrate have been analyzed according to the model and the activation energy for monomers diffusion at the oxide surface estimated on the basis of scaling laws.