The composition dependence and orientation anisotropy of the dielectric and ferroelectric properties of epitaxial Pb(ZrxTi1−x)O3 (PZT) thin films grown using metalorganic chemical vapor deposition were investigated. {100}-, {110}-, and {111}-oriented PZT films were ascertained to have been grown on (100)c, (110)c, and (111)cSrRuO3//SrTiO3 substrates, respectively. The relative dielectric constant reached a maximum near x=0.5, around the morphotropic phase boundary (MPB) composition, irrespective of film orientation, with the {111}-oriented film showing the largest value. Well-saturated hysteresis loops were observed for all films, and abrupt saturation of the remanent polarization (Pr) and coercive field (Ec) values were observed when the value of x was small, irrespective of film orientation. The Ec value reached a minimum around the composition for {110}- and {111}-oriented films but not for {100}-oriented ones. The saturated polarization (Psat) and Pr values for the {111}-oriented film reached a maximum around the MPB composition, while attaining a minimum for films with other orientations. The ratio of Pr to Psat decreased near the MPB composition regardless of film orientation. These results suggest that the electrical properties of epitaxial PZT thin films strongly depend on both of the composition and orientation of the films.

Pb(Zr, Ti)O3 (PZT) thin films with Zr/(Zr+Ti) of 0.42 were prepared on (111)Pt/Ti/SiO2/Si substrates at 620°C by metalorganic chemical vapor deposition (MOCVD). We attempted the pulse introduction of a mixture of source gases into the reaction chamber and succeeded in simultaneous improvements of the crystallinity, surface roughness and electrical properties of the PZT film by this preparation method. The (111)-orientation increased and the surface roughness decreased. Moreover, the leakage decreased and well-saturated symmetrical polarization-electric field (P-E) hysteresis loop were obtained. Remanent polarization (P r) and the coercive field (E c) values of this pulse-MOCVD film were 44 µC/cm2 and 85 kV/cm, respectively.

Epitaxial Pb(ZrxTi1−x)O3 films with (001) and (100), (101) and (110), and (111) orientations were grown on (100)SrRuO3//(100)SrTiO3, (110)SrRuO3//(110)SrTiO3, and (111)SrRuO3//(111)SrTiO3 substrates, respectively. The two composition films with Zr/(Zr+Ti) ratios of 0.42 and 0.68 were prepared with the Pb/(Pb+Zr+Ti) ratio of 0.5. Well saturated and good square shape hysteresis loops with large remanent polarization (Pr) above 40 μC/cm2 were observed for all films. The Pr increased in the following order: (101), (111), and (001) orientations for the film with the Zr/(Zr+Ti) ratio of 0.42 and (100), (110), and (111) orientations for the Zr/(Zr+Ti) ratio of 0.68. On the other hand, the Ec value mainly depended on the Zr/(Zr+Ti) ratio and not on the orientation of the film; the Ec value of the film with a Zr/(Zr+Ti) ratio of 0.42 was larger than that of 0.68. The saturation behavior did not strongly depend on the orientation, especially for the films with the Zr/(Zr+Ti) ratio of 0.42. The frequency dependence of the dielectric constant was small regardless of the orientation of the films with a Zr/(Zr+Ti) ratio of 0.42. On the other hand, for 0.68, it was also small for the (100) and (110) orientations, but increased by about 15% from 103 to 106 Hz for the (111) orientation due to the relative large leakage. The (101)-oriented film with the Zr/(Zr+Ti) ratio of 0.42 and the (100)- and (111)-oriented films with 0.68 did not show deterioration up to 1010 switching cycles.

We prepared Pb(Zr x , Ti1-x )O3 [PZT] thin films on (111)Pt/Ti/SiO2/Si substrates at 620°C by metalorganic chemical vapor deposition (MOCVD). PZT [Zr/(Zr+Ti)=0.68] thin films of different thicknesses prepared by the conventional continuous source gas introduction MOCVD (continuous-MOCVD) and by pulsed gas introduction MOCVD (pulse-MOCVD) were compared to investigate the growth mechanism of these films. Stoichiometric PZT films were obtained for a wider range of Pb source input gas flow rates under fixed Zr and Ti sources for pulse-MOCVD compared with that for continuous-MOCVD. Highly (111)-oriented films were obtained for pulse-MOCVD regardless of their thickness, while the (111)-orientation decreased with film thickness for continuous-MOCVD. This suggests that the orientation homogeneity along the film thickness is higher for pulse-MOCVD films than for continuous-MOCVD films. The surface roughness of the pulse-MOCVD films was smaller than that of the continuous-MOCVD films and this result corresponds to the decrease of the leakage current density of the film. Well-saturated hysteresis loops with good square shapes were obtained, and the remanent polarization (P r) and the coercive field (E c) values of 100-nm-thick films prepared by pulse-MOCVD were 37 µC/cm2 and 82 kV/cm, respectively.

We prepared Pb(Zr,Ti)O 3 [PZT] thin films on (111)Pt/Ti/SiO 2 /Si substrates at 395 to 580 • C by metalorganic chemical vapor deposition (MOCVD). PZT thin films with Zr/(Zr + Ti) = 0.62 prepared by conventional continuous source gas introduction (continuous-MOCVD) and pulse introduction (pulse-MOCVD) were compared. Film with higher crystallinity and smoother surfaces were obtained by pulse-MOCVD compared with continuous-MOCVD. Moreover, the leakage current density of the film decreased and ferroelectricity increased with pulse-MOCVD. Ferroelectricity decreased with decreasing the deposition temperature, but the remanent polarization (Pr) value was 22.5 µC/cm 2 for the film with a 5 nm-thick PbTiO 3 buffer layer deposited at 395 • C by pulse-MOCVD, while ferroelectricity was not obtained for the film deposited by continuous-MOCVD at the same deposition temperature.