Reduction of droplet emission and target roughening in laser ablation and deposition of metals

Abstract

The droplet concentration in laser-deposited metal, Si, and alloy thin films is studied. It is found for these materials that the number of droplets is strongly dependent on the laser fluence and is low at high laser fluences. This behavior is contradictory to what is usually observed for oxidic materials. It is also found that the amount and average size of the droplets correlate closely with the surface roughness. Rough surfaces generally emit more droplets. The target used in laser ablation and deposition experiments usually roughens during ablation. By intelligently varying the azimuthal angle of incidence, the roughening, and thereby the emission of droplets, can be greatly reduced.