Laser-induced surface perturbations in silicon

In this paper it is shown that the initial stages in the laser-induced roug hening 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 f ew hundred laser pulses strongly depends on the crystallographic orientatio n of the surface. The morphological features that appear in this first stag e have been related to the nature of the solidification process that follow s laser melting. A second stage in the roughening process with a dramatic c han-e in morphology takes place when a surface with deep depressions and hi lls is further irradiated in SF6 Very deep etching occurs in the depression s promoting the fort-nation of microholes that with further irradiation lea d to cone formation. It is further shown that the distance between microhol es is equal to the distance between the depressions that formed as the init ial perturbations developed. Then the wavelength of the initial perturbatio n and by extension the distance between microholes has been estimated.