The action of molecular interaction between a fluid and an adsorbent results in adsorption and wetting phenomena. However, the adsorbent is also submitted to the action of the molecular forces. In order to provide a large adsorption capacity, adsorbents with a large specific surface area are preferable. For this reason, for the study of adsorption phenomena, porous silicon is a material of great interest. Wetting phenomena in porous silicon layers are experimentally investigated by Raman scattering. The experimental results prove a reversible blue-shift of Raman spectra of wetted porous silicon layers with isopropanol or ethanol with respect to unperturbed layers. We ascribe the shift to a compressive stress due to the increased lattice mismatch between the porous silicon layer and the bulk silicon substrate in wetting conditions. The use of two liquids having quite similar density and surface tension resulted, as …