A simple formalism for the prediction of angular distributions in laser ablation deposition

Abstract

An analytical model allowing the quantitative description of gas clouds generated by near-threshold laser ablation is described. The model is based on a continuum description of the expansion of an idealized laser-generated gas cloud. This analysis yields the time- and space-dependent gas density and the angular intensity distribution. Dependencies of the angular intensity distribution on experimental variables (laser fluence, atom mass and laser spot size) are determined. It is found that the laser spot dimensions are most important parameters in determining the angular distribution. For a circular spot, a simple formula is derived which allows quantitative prediction of angular distributions. These predictions are in good agreement with the angular distributions of ablation plumes reported in the literature. Finally, recommendations towards deposition practice are given.