Substrate effects on the structure and optical properties of epitaxial PbTiO(sub 3) thin films prepared by metal-organic chemical vapor deposition

摘要

Epitaxial PbTiO(sub 3) films were prepared by metal-organic chemical vapor deposition (MOCVD) on MgO(001), SrTiO(sub 3)(001) and LaAlO(sub 3)(001) surfaces. Four-circle X-ray diffraction and optical waveguiding experiments were performed to characterize the deposited films. The films on all three substrates were single-crystal; however, the domain structure of the films was strongly dependent on the substrate material. Films on MgO and LaAIO(sub 3) substrates showed a large amount of 90(degrees) domain structures, whereas, the degree of twinning was greatly suppressed for films on SrTiO(sub 3). The refractive indices and optical birefringence of the films were measured as a function of wavelength using the film-prism coupling method. The authors found that for films on LaAIO(sub 3)(001), the ordinary index and for films on MgO(001) both the ordinary and extraordinary refractive indices were higher than those of bulk single-crystal PbTiO(sub 3). For films grown on SrTiO(sub 3)(001), the ordinary refractive index was very close to that of single crystal PbTiO(sub 3). They correlate the increased refractive index and the reduced birefringence to the degree of epitaxial strain and twinning in the samples, respectively.