Second harmonic generation ( SHG) may be an important tool to probe buried solid/liquid interfaces because of its inherent surface sensitivity. A detailed interpretation of dye adsorption onto Si-SiO2 wafer is not straightforward because both adsorbent and adsorbate contribute to the overall SHG signal. The polarization resolved SHG analysis points out that the adsorbent and adsorbate contributions are out of phase by pi/2 in the present system. The surface nonlinear susceptibility chi((2)) represents thus a complex tensor in which its real part is related to the adsorbent contribution and its imaginary part to the adsorbate one. (C) 2016 Elsevier B. V. All rights reserved.