Laser-induced surface perturbations in silicon

In this paper it is shown that the initial stages in the laser-induced roughening in silicon is independent of the atmosphere used, whether it is Ar, vacuum, or SF₆. It is also shown that the morphology that results after a few hundred laser pulses strongly depends on the crystallographic orientation of the surface. The morphological features that appear in this first stage have been related to the nature of the solidification process that follows laser melting. A second stage in the roughening process with a dramatic change in morphology takes place when a surface with deep depressions and hills is further irradiated in SF₆. Very deep etching occurs in the depressions promoting the formation of microholes that with further irradiation lead to cone formation. It is further shown that the distance between microholes is equal to the distance between the depressions that formed as the initial perturbations developed. Then the wavelength of the initial perturbation and by extension the distance between microholes has been estimated.