Low index surfaces are in most cases stable even after adsorption, whereas
vicinal surfaces may be only stable without or even with adsorbates. Since
these phenomena are rather frequently reported, some carefully studied exam
ples are discussed here, to show the importance of the effect and possible
reasons for the sometimes dramatic morphology changes. Metals on semiconduc
tors and metals are well studied and therefore the best examples for the pr
esent purpose. Since vacancies at the surface may act as point defects in a
similar way, f-centers on NaCl are included into the discussion. (C) 1998
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