The present work is concentrated on the investigation of the initial stages of growth of Ge nanoparticles embedded in an amorphous A1203 matrix on suitable substrates. The growth technique is based on self-organization processes related to the balance of the interface energies involved. Combined data from complementary optical techniques (absorption, Raman scattering, spectroscopic ellipsometry) give evidence of a behaviour which can be ascribed to the existence of a wetting layer, not detectable by conventional transmission microscopy.