Azo dye molecules were grafted onto a silicon wafer surface in order to generate a potentially orienting substrate interface for liquid-crystal (LC) layers. This coupling agent was synthesized by reaction between 4-[bis(2-hydroxyethyl)amino]-4'-nitro azobenzene (DR19) and 3-(triethoxysilyl)propyl isocyanate (TESPI). The H-1-NMR, LR spectra of the silylated compound confirmed that nucleophilic addition between the carbonyl group of TESPI and the hydroxyl functions of DR19 had occurred. In this article, the silanization conditions are described and the thin layers obtained characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray reflectivity.