Structural analysis in (100)/(001)-oriented epitaxial lead titanate thick films grown by MOCVD for MEMS application

(100)/(001)-oriented epitaxial PbTiO₃ films were grown on (100) SrTiO₃ and (100) Nb-SrTiO₃ substrates by MOCVD. The detailed domain structure of these films was analyzed by X-ray diffraction pattern and piezoresponse force microscopy. In thick films (over 1.1 mum), much more complex domain structure has been observed compared to thin films. Domain structures of thick films consist of one kind of c-domains (c₁ ) and three kinds of a-domains (a₁ , a₂ and a₃ ). The tilting angles of a ₂/a ₃ and a₁ /c₁ boundaries are about 3.6deg which corresponds to the inclination angle given by geometric calculation, 2arctan(c/a)-90deg, where a and c are lattice parameters of strain-free state of PbTiO₃ . Other domain boundaries, a₂ /c₁ and a₁/a₃, are strained ones with rotation, and have not been observed in thinner films. It is assumed that this complex domain structure was formed through the strain relaxation of thick PbTiO₃ films.