Self-organization of ordered surface patterns in nearly free sustained Al films

Abstract

A nearly free sustained aluminum film system has been successfully fabricated o n liquid substrates by thermal evaporation method. The ordered surface pattern s with band-shaped structure, propagating from the film edges to the central reg ions, are systematically studied. The formation of these patterns is strongly d ependent on the experimental conditions (such as the nominal film thickness, de position rate, growth period in vacuum etc.) and the growth mechanism can be tra ced to a three-stage process. The experiment proves that the ordered patterns re sult from the free diffusion and aggregation of the Al atoms and atomic clusters on the liquid surfaces driven by the internal stress. Further theoretical analy sis shows that due to the characteristic boundary condition and interactions bet ween the metallic films and the liquid substrates, the nearly free sustained Al films may contain a series of sinusoidal stress distributions with different amp litudes and frequencies, and their composition results in the formation of the o rdered surface patterns.