  The propagation of sidewall steps during the growth of nanowires is
calculated in the frame of the Burton-Cabrera-Frank model. The stable shape of
the nanowire comprises a cylinder section on top of a cone section: their
characteristics are obtained as a function of the radius of the
catalyst-nanowire area, the desorption-limited diffusion length of adatoms on
the terraces, and the sticking of adatoms at step edges. The comparison with
experimental data allows us to evaluate these last two parameters for InP and
ZnTe nanowires; it reveals a different behavior for the two materials, related
to a difference by an order of magnitude of the desorption-limited diffusion
length.
