  From a macroscopic point of view phase transitions as surface melting or two
dimensional (2D) towards three dimensional (3D) growth mode (Stranski-Krastanov
transition) can be described in terms of Gibbs excess quantity duly amended by
size effects (since usual Gibbs excess quantities are only well defined for
semi-infinite systems). The aim of this study is to consider such amended
quantities to describe surface melting and Stranski-Krastanov transition of
epitaxial layers. the so-introduced size effects allows us to predict the
equilibrium thickness of the wetting layer of the Stranski-Krastanov growth
mode and to describe and classify two different melting cases: the incomplete
melting relayed by a first order transition and the continuous premelting
relayed by continuous overheating
