Development of Strain-induced ferroerectlic Thin Films Prepared by MOCVD

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Strain effect on the ferroelectricity of the film was investigated. The degree of c-axis orientation increased when Nb content increased in Pb (Ti, Nb) O_3 film deposited on (100) MgO substrates. Lattice parameter ratio of c- to a-axis (c/a) decreased with increasing Nb content. Increase of the degree of c-axis orientation with decreasing c/a ratio which was commonly observed for Pb (Ti, Nb) O_3, Pb (Ti, Al) O_3 and Pb (Zr, Ti) O_3 films. These can be explained by the stress applied to the film.Effect of the orientation of the Pb (Zr, Ti) O_3 films on the ferroerectricity was also observed. Polar-axis oriented film, (001) tetragonal-PZT and (111) rhombohedral PZT, showed the largest remnant polarization (Pr). However, the other oriented films, (101) and (111)-oriented tetragonal PZT and (110) and (100)-oriented rhombohedral PZT, showed large Pr value compared with the expected value from the calculation. This phenomena can be explained by the domain structure induced by the stress applied to the film.