A CONTINUUM MODEL FOR THIN-FILM CONDENSATION

The proposed continuum model describes thin film nucleation and growth from a unique point of view for the whole region of supersaturations (both the metastable region of small supersaturations and the unstable region of high supersaturations). The early stage of thin-film format ion is presented as a relaxation process of the order parameter field. For small metastability parameter, the nucleus-like solution of a run ning wave is found. It describes the growth and dissolution of new pha se nuclei. The continuum model is shown to conform to the classical ca pillary theory in this case. A correlation between parameters of these two theories is deduced. It is revealed that, if the metastability pa rameter is close to its critical value, then the profile of the order parameter field is strongly distorted and fluctuations of the critical nucleus touch not only the boundary but the nucleus as a whole. in th is case the nucleation process is described statistically, with the am plitude of the unstable mode chosen as a description variable. When th e supersaturation is so large that the adatom system is unstable (the number of particles in a critical nucleus is equal to unity and the me tastability parameter exceeds its critical value), the process of thin -film condensation is described in the framework of the spinodal decom position theory. in the case of sufficiently small supersaturation the energy of nucleus formation is calculated with regard to the existenc e of a transition region that separates new and initial phases.