Studio computazionale di processi microscopici rilevanti per la crescita di film semiconduttori


We present a detailed study of some atomic-scale processes fundamental in
understanding Si and Ge thin-film growth. Our research is focused on two
different systems. First, we have investigated Ge atoms surface mobility on
Ge(105). Such surface is of particular interest since it characterizes the
lateral facets of the Ge quantum dots which are spontaneously formed during
Ge growth on Si(001). Two fundamental results are reported: a) diffusion is
basically isotropic b) at the typical experimental temperatures adatoms move
really fast. Such results have been used to model the experimentally observed
morphological transition of three-dimensional Ge islands.
The second system which we considered is the hydrogenated Si(001)(1x2) surface.
By Car-Parrinello molecular dynamics simulations, we computed the probability
that a SiH3 radical, i.e. one of the key Si-film growth precursors in PECVD-like
(Plasma-Enhanced Chemical Vapor Deposition) ractors, is able to extract a
surface hydrogen during its thermal-energy impact with the surface. Our results
show a strong occurrence of such a mechanism, which thus plays an important
role in determining the film growth rate since it allows for the creation of
new reactive sites, characterized by surface dangling bonds.

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