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Epitaxial PbTiO3 (PTO) thin films were deposited on different single crystal (100)KTaO3 [KTO], (110)DyScO3 [DSO], (110) GdScO3 [GSO] and (001)SrTiO3 [STO] substrates. Temperature dependence of the lattice parameters and the domain structure showed a systematic change with misfit strains (S m) of PTO films, explored by high-resolution X-ray diffraction measurements. Fully (001)-orientation films on STO and fully (100)-orientation films on KTO substrates were confirmed, and the elevated phase transition temperature (T c) was confirmed in PTO films induced by both large compressive (STO) and tensile strains (KTO). While, for PTO films grown on GSO substrates with small tensile strains, T c is similar to the powder data. And, ferroelastic domain structure changed from (100)-orientation to (100)/(001)-orientations was observed during decreased temperature. The temperature dependence of domain structures PTO films with the different S m are in good agreement with thermodynamic calculation for the temperature–S m diagram of ferroelastic domain structure.

A new orientation control method for depositing (110)-oriented perovskite thin films was demonstrated using a (101)PdO//(111)Pd buffer layer on (100)Si substrates, which is widely used in integrated ferroelectric and dielectric applications. The (101)-oriented PdO was obtained by oxidizing (111)Pd films deposited on a (111)Pt/TiOx/SiO2/(100)Si substrate and (110)-oriented perovskites including SrRuO3 and (Ba0.5,Sr0.5)TiO3 (BST) were obtained on (101)PdO by the RF magnetron sputtering method. Although the BST films deposited at 500 °C were not crystallized, the BST films deposited above 600 °C are fully crystallized and the (110)-orientation is dominant. The (110)-oriented BST thin film showed good dielectric property with high dielectric constant (>600) at 0 kV/cm and high tunability (>50% at ±200 kV/cm). Comparing this dielectric property with those of other oriented BST films, both the dielectric constant and the tunability tend to decrease in the order of (111)-, (100)-, and (110)-preferred orientations.

Ferroelectric properties were investigated for (100), (110), and (111)-single-oriented rhombohedral Pb(Zr0.65Ti0.35)O3 films. Saturation polarization, P sat, was changed by the simple tilting angle of the polar axis from the film surface normal. On the other hand, (100)- and -oriented films prepared on (100) Si substrates showed similar P sat values due to the coexistence of orientation. The coercive field, E c, of rhombohedral Pb(Zr0.65Ti0.35)O3 films was lower than that of tetragonal Pb(Zr0.4Ti0.6)O3 films. (100)-oriented rhombohedral films with SrRuO3 electrodes did not show noticeable degradation in polarization up to 1010 switching cycles. These results show that (100)-oriented rhombohedral Pb(Zr x Ti1− x )O3 film is available to realize the low voltage operated ferroelectric random access memory instead of the present tetragonal Pb(Zr x Ti1− x )O3 films.

100-oriented epitaxial Pb(Zr,Ti)O3 [PZT] films with various Zr/(Zr+Ti) ratios from 0 to 0.8 were grown on (100)c SrRuO3∥(100) SrTiO3 and (100)c SrRuO3∥(100) LaNiO3∥(001) CaF2 substrates. 200-nm-thick films grown on CaF2 substrates consisted of a pure tetragonal phase up to the Zr/(Zr+Ti) ratio of 0.8. On the other hand, the phase of the films on SrTiO3 substrates changed from pure tetragonal below the Zr/(Zr+Ti) ratio of 0.4 to rhombohedral above the Zr/(Zr+Ti) ratio of 0.6 through their mixture phase within the Zr/(Zr+Ti) ratio range from 0.4 to 0.6. The larger polarization value was observed to be lager for PZT films on CaF2 substrates than for PZT films on SrTiO3 substrates for all Zr/(Zr+Ti) ratios and was in good agreement with the estimated one assuming tetragonal symmetry. The tetragonal region can be expanded to a Zr/(Zr+Ti) ratio of 0.8 below 1 µm in thickness for films on CaF2 substrates. The present results show that the large thermal strain induced by CaF2 substrates having with a large thermal expansion coefficient can expand the tetragonal symmetry region up to large a Zr/(Zr+Ti) ratio and thicker films.

Squareness in polarization–electric field hysteresis loops of (100)-oriented epitaxial and fiber-textured rhombohedral Pb(Zr,Ti)O3 films prepared on (100) SrTiO3 and (100) Si substrates, respectively, was investigated as a function of temperature. The ratio of remanent polarization to saturation polarization (P r/P sat) decreased with increasing temperature for all films. It depends on the kind of substrates and the remained strain in the in-plane orientation. These data suggest that the existing strain in the films possibly affects the temperature dependence of the P r/P sat ratio.

Films of a high-pressure perovskite phase, Bi(Mg1/2Ti1/2)O3, were prepared on (111)c-oriented SuRuO3-coated (111)Pt/TiO2/SiO2/(100)Si substrates. The perovskite Bi(Mg1/2Ti1/2)O3 films had a (111) one-axis orientation, because their constituent grains were epitaxially grown on (111)c-oriented perovskite SrRuO3 ones. The remanent polarization and piezoelectric constant measured at an applied electric field of 600 kV/cm were about 30 µC/cm2 and 40 pm/V, respectively. A remarkable phase transition was not observed from room temperature to 350 °C in a (111) one-axis-oriented Bi(Mg1/2Ti1/2)O3 film, suggesting that the Curie temperature of this film is above 350 °C.

The origin of the ferroelectricity of Bi(Mg1/2Ti1/2)O3 films was investigated. Epitaxial Bi(Mg1/2Ti1/2)O3 films with film thicknesses of 50 to 800 nm were grown on (111)cSrRuO3/(111)SrTiO3 substrates by pulsed laser deposition. A Bi(Mg1/2Ti1/2)O3 film was not strongly clamped from the substrate and identified to have rhombohedral symmetry with a = 0.398 nm and α= 89.8°, which was independent of film thickness within 100 to 800 nm. The relative dielectric constant, remanent polarization, and coercive field of the Bi(Mg1/2Ti1/2)O3 films at room temperature were almost constant at about 250, 60 µC/cm2, and 240 kV/cm, respectively, for film thicknesses above 200 nm. These data suggest that Bi(Mg1/2Ti1/2)O3 films are ferroelectric.

100-oriented epitaxial Pb(Zr0.65Ti0.35)O3 films with various film thicknesses from 0.1 to 3 µm were grown on (100) c SrRuO3 ∥ (100)SrTiO3 and (100) c SrRuO3 ∥ (100)LaNiO3 ∥ (001)CaF2 substrates. The out-of-plane/in-plane lattice parameter ratio of the films on the CaF2 substrates was larger than that on the SrTiO3 substrates up to 1.1 µm film thickness, while (90°-α) (α was defined as the internal tilt angle) was almost 0°. Results of analysis of Raman spectra and piezoresponse images suggest that the 1.1-µm-thick film grown on the (100) c SrRuO3 ∥ (100)LaNiO3 ∥ (001)CaF2 substrate had tetragonal symmetry with a polar-axis orientation. Moreover, the saturation polarization values of the films measured from P–E hysteresis loops correspond to the two P s values estimated from the thermodynamic theory, assuming the change in the polar direction due to the symmetry change to tetragonal, and from the crystal distortion in tetragonal symmetry. This can be explained by the large compressive stress from the CaF2 substrate having a large thermal expansion coefficient.

In this paper we investigated the intrinsic impact of Bi(Zn 1/2Ti1/2)O3 (BZT) addition on the crystallographic and ferroelectric properties of Pb(Zr 0.4Ti0.6)O3 (PZT) thin films deposited by sol-gel technique. We could emphasis the shrinkage of lattice parameters, leading to a decrease of spontaneous polarization, with increasingly BZT content. This result is coherent with predicted evolution of spontaneous polarization with unit cell tetragonality.

Thin films of SrBi4Ti4O15, a kind of bismuth layer-structured dielectrics (BLSDs), were prepared on platinized silicon wafers buffered by perovskite-type oxide interface layers, (100)LaNiO3/(111)Pt/TiO2/(100)Si and (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si, by chemical solution deposition (CSD). The Ca2Nb3O10 nanosheets were supported on a (111)Pt/TiO2/(100)Si substrate by dip coating using an aqueous dispersion, while (100)LaNiO3 was prepared by CSD. The (00l) planes of BLSD crystal were preferentially oriented on the surface of both substrates, which is caused by suitable lattice matching between the a-(b-)axis of BLSD and perovskite-type oxide layers. The film deposition on (001)Ca2Nb3O10 nanosheets yielded (001)-oriented BLSD films with higher crystallinity and smaller fluctuation in the tilting angle of the (001)BLSD plane than those on the (100)LaNiO3 interface layer. The dielectric constant (εr) of (001)-oriented SrBi4Ti4O15 film on (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si substrate was approximately 190, which was significantly stable against the change of frequency and bias voltage compared with that of the randomly-oriented SrBi4Ti4O15 film.

The structural property and electric field response of a single perovskite PbTiO3 nanowire were investigated by means of synchrotron X-ray diffraction (XRD) with a micro X-ray beam. XRD θ–2θ patterns and Raman spectra confirmed the formation of the perovskite phase of PbTiO3 by annealing the PX-phase of Pb–Ti–O nanowires at 600 °C. In addition, the obtained nanowires showed multi-domain/grain features. By focusing the micro X-ray beam on a single perovskite PbTiO3 nanowire, both ends of which are connected to electrodes, the lattice distortion under the electric field was observed.