Transient nucleation on inhomogeneous foreign substrate

Nucleation from the vapor phase on a foreign substrate with a low number of inhomogeneities is studied. Kinetic equations describing the 3D nucleation on active sites are solved numerically. It is shown that the cluster flux (i.e., the rate of formation of nuclei of a given size) reaches some extremal value at certain time and then tends to zero as time increases. In such a sense, formation of nuclei is a fully nonstationary process, in contrast to the standard nucleation theory. The total number of nuclei formed on a unit surface reaches for a sufficiently long time some stationary value, which is close to the number of nucleation active sites.