Multi-layered LiNbO3 films prepared by a polymeric precursor method

The polymeric precursor method was used to prepare multi-layered LiNbO3 films. The overall process consists of preparing a coating solution from the Pechini process and the deposited film is subsequently heat-treated. Two-layered films were prepared by this process, onto (0001) sapphire substrates. Two different routes were investigated for the heat-treatment. The “amorphous route” consisted of performing, after each deposition, a pre-treatment at low temperature to eliminate the organic material. In this case, the crystallization heat-treatment was performed only after the two layers had been deposited. On the other hand, a process “layer-after-layer crystallization” was used. Both routes led to (000l) LiNbO3 oriented films. However, only the film prepared by the “layer-after-layer crystallization” presented an epitaxial growth and a crack-free morphology. Moreover, the “layer-after-layer crystallization” process led to a film exhibiting the best optical properties.