Condensation of vapor and nanoclusters formation within the vapor plume, produced by ns-laser ablation of Si

The condensation within the expanding vapor plume produced by ns-laser ablation is discussed within the frame of Zeldovich and Raizer theory of condensation. The calculations have been done for the Si vapor. It is shown that the size of clusters formed during the condensation is very small because of fast expansion of the plume and quenching phenomena. The average cluster radius is calculated for different temperatures and densities of initial plume and it is typically of the order of few nanometers. The generalization of the theory is made for inhomogeneous plume where the rates of nucleation as well as condensation times are different for different parts of the plume. As a result, the distribution in cluster's size appears. Nevertheless, this distribution function is very sharp for the plume expanding in vacuum. For the clusters moving together with vapor one can distinguish three different waves propagating through the plume: (1) wave of saturation where the vapor becomes saturated, (2) supercooling wave where the highest supercooling is reached, and (3) the quenching wave. Parameters for these waves are calculated. The possibility of oscillation phenomena during condensation is discussed as well.