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.
PbO, ZrO2, TiO2 and Pb(Zr
x
Ti1-x
)O3 (PZT) films were prepared by metalorganic chemical vapor deposition
(MOCVD) using Pb(C11H19O2)2, Zr(O·t-C4H9)4, Ti(O·i-C3H7)4 and O2 as source materials. The
deposition rates of the constituent metals of Pb(Zr
x
Ti1-x
)O3 (PZT) film were investigated as
functions of the input gas flow rate of the source materials and the deposition temperature.
Composition ratios of the PZT film became constant when the Ar carrier gas flow rate of the Pb
source was above 100 cm3/min at 500°C. This suggests that a self-correcting composition region
exists for this input gas composition at 500°C. The deposition rates of each of the constituent
metals of the PZT films were quite different from those in the corresponding single-oxide films, PbO,
ZrO2, and TiO2 films. Therefore, the composition ratio of the PZT film could not be estimated
from the deposition rates of the corresponding single-oxide films. The deposition temperature
dependence of the deposition rates of Ti and Zr in the PZT films was almost the same. This
results in the Zr/(Zr+Ti) ratio being independent of the deposition temperature. However, the
deposition behavior of Pb was different from those of Ti and Zr. Therefore, the Pb/(Pb+Zr+Ti)
ratio must be adjusted by changing the input gas flow rate of the Pb source when the deposition
temperature is changed.
A new type of scanning nonlinear dielectric microscope (SNDM), with an additional function of simultaneous observations of surface morphology, has been developed. This was achieved by employing an electrically conducting atomic force microscopy cantilever as a probe needle. Using this new SNDM, simultaneous measurements of several ferroelectric materials, such as lead zirconate titanate (PZT) thin films on both SrTiO3 and MgO substrates, were performed. Topographic and domain images were simultaneously obtained from the same location on the materials. Finally, the resolution of the SNDM was theoretically calculated and it was revealed that atomic scale resolution is possible using the SNDM technique.
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