Nucleation and growth of clusters on heterogeneous surfaces

A thin film growth model, with the consideration of the transient nucleation and surface heterogeneity, was proposed to simulate the nucleation and growth rates of clusters in the physical vapor deposition. The process is divided into a sequence of time stages in order to solve the time dependent problem. The concentration of the adatoms is obtained by solving the adatom diffusion equations around the stable clusters. The effect of surface heterogeneity was treated by a suitable distribution of contact angle of the condensate on the substrate. The results show that a surface with higher heterogeneity will lead to a higher nucleation rate and cluster density. However, the clusters grow slowly due to the serious depletion of adatom by the existing clusters and thus, the clusters distribute more narrowly and a fine-grain polycrystal structure is resulted. The importance of the transient stage was also compared between the cases of complete and incomplete condensation. The simulation result shows that the transient stage can not be neglected in the completed condensation.