TiO2(Ln) films deposited by the sol-gel and dip coating technique on Si wafers and soda-lime glass as substrates have been characterized by spectroscopic ellipsometry, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. Among the various factors that affect the optical and structural properties of oxide films we focus in this paper on the substrate and the lanthanides (La, Eu, Sm, Gd) as dopants.