Residual stresses and clamped thermal expansion in LiNbO_3 and LiTaO_3 thin films

摘要

Residual stresses in LiNbO_3 and LiTaO_3 epitaxial thin films were evaluated taking into account Li nonstoichiometry by means of Raman spectroscopy and x-ray diffraction. The epitaxial films were grown on C-cut sapphire substrates by pulsed injection metal organic chemical vapour deposition. Clamping of the epitaxial films by the substrate induced a transfer from the in plane thermal expansion to the out of plane component. The temperature of the phase transition of clamped LiTaO_3 films was close to that expected for a bulk sample.