Electro-optic characterization of sol-gel derived (Pb,La)TiO₃ thin films

Highly oriented lead lanthanum titanate ((Pb_1-xLa_x)TiO₃, let it call PLTx) thin films have been prepared on MgO and sapphire substrates by sol-gel method. XRD analyses confirm that the PLT films fabricated on MgO(100) and c-plane sapphire substrates grow highly preferentially to (100) and (111) orientations, respectively. The film composition affects the structure of PLT film as well as the optical properties such as the refractive index and the electro-optic characteristics. As La content in the film increases, it is found that the tetragonal structure of the PLT films changes to cubic structure in the film. Also, the electro-optic coefficient of the film decreases as the La content increases since the anisotropy of the refractive index decreases.