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(100)/(001)-oriented 2 μm-thick Pb(Ti, Zr)O3, films with the Zr/(Zr + Ti) ratio of 0.39 and 0.50 were prepared by metalorganic chemical vapor deposition. The volume fraction of (001)-oriented domain, Vc, was controlled by selecting the kinds of substrates with different thermal expansion coefficient. The effective piezoelectric constant increased up to 310 pm/V with decreasing the Vc and tetragonality (lattice parameter ratio of c axis to a axis) determined by the decrease of the Zr/(Zr + Ti) ratio. Observed large piezoelectric response was considered to be mainly contributed by the extrinsic effect, such as the 90o domain switching. These experimental inputs suggest the new concept for enhancement of the piezoelectric properties. [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr,Ti)O3 (PZT) thick films of 2.0–3.0 μm thickness were grown at 600 °C on (100)cSrRuO3∥(100)SrTiO3 and (100)cSrRuO3∥(100)LaNiO3∥(100)CaF2 substrates by pulsed-metal organic chemical vapor deposition. All films showed (100) and/or (001) orientations with tetragonal symmetry. It was found that there is an almost linear relationship between the estimated thermal strain from the deposition temperature to the Curie temperature and the volume fraction of (001) orientation in the mixture of (100) and (001) orientations for the films on both substrates. Consequently, the perfectly (001)-oriented, i.e., polar-axis-oriented, PZT thick films were obtained on CaF2 with the Zr/(Zr+Ti) ratio from 0.20 to 0.40. Moreover, the lattice parameter of a- and c-axes and their ratio (c/a) of those polar-axis-oriented films were almost the same as the reported data for the powder, suggesting that the large strain is not remaining in those films. The relative dielectric constant ([variant_greek_epsilon]r) of the polar-axis-oriented Pb(Zr0.35Ti0.65)O3 thick film on CaF2 was 180 at 1 kHz, which is lower than that of (100)/(001)-oriented thick films on SrTiO3 but almost agrees with the theoretically calculated value for the c-axis of PZT single crystals. Well saturated polarization-electric-field hysteresis loops with a good square shape were observed for the polar-axis-oriented thick films, and the saturation polarization and the coercive field values were 74 μC/cm2 and 64 kV/cm, respectively. These data clearly show that the electrical properties of the polar-axis-oriented epitaxial thick films are similar to the theoretical predictions for PZT single crystals. [ABSTRACT FROM AUTHOR]

Epitaxial (100)/(001)-oriented tetragonal Pb(Zr,Ti)O3 films above 1 μm thick were grown on (100)SrTO3 substrates by pulsed metal organic chemical vapor deposition, and the films with Zr/(Zr+Ti) ratios up to 0.43 were found to have a strain-relaxed domain structure. The domain structure determined by the volume fraction of (001) orientation (mainly decided by the thermal strain above the Curie temperature) and the lattice parameters dependent on the Zr/(Zr+Ti) ratio are explained by a geometrical model consistent with previous results for PbTiO3 films [J. Appl. Phys. 104, 064121 (2008)]. [ABSTRACT FROM AUTHOR]

Epitaxial (100)/(001)-oriented PbTiO3 films with thickness of 2.8 μm were grown on Nb-doped (100) SrTiO3 substrates by pulsed metal organic chemical vapor deposition. Complex domain structures consisting of c-domains (c1) and three types of a-domains (a1, a2, and a3) were observed by piezoresponse force microscopy in conjunction with high-resolution x-ray diffraction analysis. The obtained results suggest that (a2/a3) and (a1/c1) domain configurations represent mostly strain-relaxed structures. This conclusion is in good agreement with theoretical predictions made for thick films [Phys. State., Solidi 37, 329 (1976)]. [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr, Ti)[O.sub.3] (PZT) thick films are grown on (100)SrRu[O.sub.3]/(100)SrTi[O.sub.3] and (100)SrRu[O.sub.3]/(100)LaNi[O.sub.3]/(100)Ca[F.sub.2] substrates by pulsed-metal organic chemical vapor symmetry. The studies have shown that the electrical properties of the polar-axis-oriented epitaxial thick films are similar to the predictions for PZT single crystals.

Epitaxial (100)/(001)-oriented tetragonal Pb(Zr, Ti)[O.sub.3] films are grown on (100)SrT[O.sub.3] substrates by pulsed metal organic chemical vapor deposition and the films with Zr/(Zr+Ti) ratios have a strain-relaxed domain structure. The domain structure determined by the volume fraction of (001) orientation and the lattice parameters dependent on the Zr/(Zr+Ti) ratio are described by a geometrical model consistent with previous results for PbTi[O.sub.3] films.

The occupation sites of Dy- or Y-substituted PZT films were identified using Raman spectroscopy, and the correlation between the occupation site and ferroelectric property was investigated. When Dy or Y was less than 2%, the ferroelectric properties improved because substitution occurred at the B-sites of the PZT films. However, the ferroelectric properties decreased when the substituted ions exceeded 4% because substitution occurred at both B- and A-sites. Consequently, it is important to accurately introduce substituted ions into the B-sites in a PZT film to improve the ferroelectric properties. [ABSTRACT FROM AUTHOR]

Tetragonal Pb(Zr, Ti)O3 films were epitaxially grown on SrRuO3-coated SrTiO3 substrates by metal organic chemical vapor deposition. Perfect polar-axis-oriented 50 nm thick tetragonal films were successfully grown on (100)SrRuO3//(100)SrTiO3 substrates. The single phase of the tetragonal symmetry region was expanded to a Zr/(Zr + Ti) ratio of around 0.6 for these films but was reduced to around 0.4 when (100)/(001)-mixture oriented 250 nm thick films were obtained. The dependence of spontaneous polarization (Ps) on the lattice parameter of c-axis to a-axis (c/a ratio) was demonstrated using perfectly polar-axis-oriented films with various Zr/(Zr + Ti) ratios. The 250 nm thick (100)/(001), (110)/(101), and (111)-oriented tetragonal films were grown on (100), (110), and (111)-oriented substrates. The domain structure was analyzed in detail, and it was found that the observed saturation polarization (Psat) value can be explained by the Ps value and the 90° domain contribution. These data clearly demonstrate the importance of epitaxial film research for actual ferroelectric random access memories applications. [ABSTRACT FROM AUTHOR]

We employed in situ Raman spectroscopy under electric field for (100)/(001)-oriented tetragonal Pb(Ti0.61Zr0.39)O3 films with (001)-volume fraction (VC) of 35%. The increase in VC was revealed above 200 kV/cm, which resulted in the larger remanent polarization. In addition, the application of high enough field also brings a feature, i.e., large reversible change in VC with/without electric field that can quantitatively explain the enhanced piezoelectric response. These demonstrate the usefulness of in situ Raman observation to probe the domain contributions to the electrical and piezoelectric responses. [ABSTRACT FROM AUTHOR]

(100)/(001)-oriented epitaxial PbTiO3 films thicker than 1 μm were grown on various types of substrates by chemical vapor deposition. The domain structures of these films with different volume fractions of (001) were investigated. Domain structures, consisting of (100)/(001)-oriented domains, were observed regardless of the type of substrate. However, the tilting angles of the a- and c-domains from the surface normal linearly changed with the volume fraction of the (001) orientation. These results suggest that the volume fraction of the (001) orientation is crucial in identifying the domain structure of PbTiO3 thick films. [ABSTRACT FROM AUTHOR]

The authors grew (001)- and (001)/(100)-oriented epitaxial PbTiO3 films with various thicknesses on (100)SrTiO3 substrates. They used x-ray diffraction to measure the angles between surface normal [001] of (001)-oriented domains and [100] of (100)-oriented domains. The angles were found to be approximately 3.6° when the film thickness exceeded 1100 nm. This value is consistent with the value obtained by a geometric calculation for strain-free PbTiO3. This result suggests that thick epitaxial PbTiO3 films grown on (100)SrTiO3 substrates have a fully strain-relaxed structure. [ABSTRACT FROM AUTHOR]

Thin films of Bi(Fe1-xScx)O3 (BFSO) system were fabricated on (111)Pt/TiO2/SiO2/(100)Si substrates by chemical solution deposition to improve the electrical resistivity by substituting electrically unstable Fe3+ cations for stable Sc3+ cations. A single phase of perovskite was obtained in the range of x=0–0.30, in which selective replacement of Fe3+ and Sc3+ was confirmed in x=0–0.15 by using Raman measurement. The leakage current density of the BFSO films was reduced by increasing x. A well-saturated polarization–electric field hysteresis loop was obtained for BFSO films with x=0.15, showing remanent polarization of approximately 35 μC/cm2. [ABSTRACT FROM AUTHOR]

Spontaneous polarization can be enhanced by increasing the crystal anisotropy of tetragonal Pb(Zr,Ti)O3 [PZT] lattice by Zr and Ti-site substitution with Dy3+ cations. Spontaneous polarization (Ps) in epitaxial film of 2% Dy3+-substituted tetragonal Pb(Zr0.40Ti0.60)O3 [Dy–PZT] was compared with that of nonsubstituted Pb(Zr0.40Ti0.60)O3 [PZT] to investigate intrinsic contribution of the Dy3+ substituion to the Ps improvement. Epitaxial thin films of PZT and Dy–PZT with (111) orientations were grown on (111)cSrRuO3//(111)Pt//(100)YSZ//(100)Si substrates by chemical solution deposition. The saturated polarization values of PZT and Dy-PZT films with (111) orientation were 41 and 48 μC/cm2, respectively. The estimated Ps values of PZT and Dy–PZT films from the saturation polarization values were 71 and 84 μC/cm2, respectively. The Ps value of this PZT was in good agreement with previous reports. The increase in Ps of the epitaxial Dy3+-substituted PZT film is attributed to the enhancement of the crystal anisotropy, i.e., tetragonality, of the tetragonal PZT lattice. This shows that the enhancement of the ferroelectricity of the tetragonal PZT films can be achieved by ion substitution, just as it can in Bi4Ti3O12-based film. [ABSTRACT FROM AUTHOR]

Using scanning X-ray microdiffraction with a 50 µmφ micro-beam and a newly developed two-dimensional detector, the crystal and domain structures were analyzed for a 2.4-µm-thick epitaxial Pb(Zr0.43Ti0.57)O3 film directly underneath a 200 µmφ Pt top-electrode before and after applying an electric field. An obvious extrinsic 90°-domain rotation was observed and the volume fraction of c-domain was increased from ∼42 to ∼71% by an applied electric field over the coercive field. This phenomenon induced a large ferroelectric remanent polarization (Pr∼60 µC/cm2) which is an unforeseeable value from an as-grown state of Pb(Zr0.43Ti0.57)O3 film. [ABSTRACT FROM AUTHOR]

(100)/(001)-oriented tetragonal Pb(Zr,Ti)O3 (PZT) films, which were thicker than 2 µm, were epitaxially grown on SrRuO3-covered (100)Si, (100)KTaO3, (100)SrTiO3, and (100)CaF2 substrates by metal organic chemical vapor deposition. The volume fraction of the (001)-orientation almost linearly increased as the thermal strain increased during the cooling process from the deposition temperature to the Curie temperature. Consequently, perfectly (001)-oriented, i.e., polar-axis-oriented, thick films were obtained on CaF2 substrates with a remanent polarization of 71 µC/cm2. This approach to grow polar-axis-oriented PZT thick films enabled the intrinsic piezoelectricity of PZT itself to be clarified, and has potential in novel applications. [ABSTRACT FROM AUTHOR]

(100)-/(001)-oriented epitaxial Pb(Zr,Ti)O3 (PZT) films with various Zr/(Zr + Ti) ratios and film thicknesses were grown on (100)cSrRuO3//(100)SrTiO3 substrates at 600°C by metalorganic chemical vapor deposition. Their crystal structure and microstructure consisting of particularly mixed phases with tetragonal and rhombohedral symmetries were investigated in detail. Films with the mixed phases with tetragonal and rhombohedral symmetries were ascertained at a Zr/(Zr + Ti) ratio of around 0.50 at a thickness of more than 200 nm from x-ray diffraction (XRD) analysis, while no mixed phase region was observed for 50 nm thick film. The relative volume fraction of the tetragonal c domain decreased with increasing film thickness for 2 µm thick films with mixed phases, while the tetragonal a domain and rhombohedral domain increased. These mixed phases were ascertained to have originated from the same cubic PZT grown above Curie temperature from results obtained by temperature-dependent high-resolution XRD reciprocal space mapping. The transmission electron microscopy images clearly revealed that the microstructure of the film gradually changed along the film thickness, despite the fact that the film was very uniform. Tetragonal phases were dominant in the bottom region (near the interface with the substrate) of the film, while rhombohedral phase was dominant in the upper region (near the surface), which was also ascertained by cross-sectional Raman analysis. In addition, the tetragonal a/c domain was wider in the bottom region than that in the upper region of film with mixed phases. These data clearly demonstrate that both the crystal structure and microstructure changed along the film thickness. [ABSTRACT FROM AUTHOR]