In the Sr–Bi–Ta–Nb–O system, three crystallographic phases are known to exist: the SrBi2(Ta1-x Nb x )O9 (SBTN) perovskite, fluorite and pyrochlore phases. It is considered that the fluorite phase is a low-temperature phase of SBT, which tends to grow in excess bismuth compositions, and the pyrochlore phase tends to grow in bismuth-deficient compositions. In conventional X-ray diffraction (XRD) characterization, the SBTN phase shows strong (115) diffraction around 29 [2θ deg]. Unfortunately, however, the other two phases also show their (111) and (222) diffractions near the same angle when the film is prepared on a platinum-coated silicon substrate. Therefore, the phase identification of the SBTN phase from the other two phases is almost impossible by the conventional technique. We employed XRD reciprocal space mapping to distinguish these phases in the present study. The three crystallographic phases were identified and distinguished from each other. It is ascertained that this technique is effective to identify crystallographic phases especially in the case in which more than two phases show similar diffraction angles.

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A simple empirical formula has been found which factors out the gross target dependence of single ionization cross sections by positron and electron impact. The formula can be used to estimate cross sections for an atom if the cross section maxima for any other two atoms in the same column of the periodic table are known. Further investigation is required to understand the basic physical mechanism underlying the degree of accuracy of such a factorization.

SrBi2Ta2O9 thin films were prepared with high compositional reproducibility by metalorganic chemical vapor deposition (MOCVD) using Bi(CH3)3, Sr[Ta(O·C2H5)6]2 and O2 as source materials. When the deposition temperature was increased, the Bi/Ta and Sr/Ta ratios in the film increased and decreased, respectively. This behavior can be estimated from the deposition temperature dependence of Bi2O3 and Sr–Ta–O films deposited from Bi(CH3)3–O2 and Sr[Ta(O·C2H5)6]2–O2 systems, respectively. Bi/Ta ratio can be controlled by the input gas concentration ratio of Bi(CH3)3 to Sr[Ta(O·C2H5)6]2 at 600°C. On the other hand, Sr/Ta ratio was independent of the input gas concentration. An almost single phase of SrBi2Ta2O9 was deposited at 670°C. The remanent polarization and the coercive field of the film deposited at 670°C following heat treatment at 750°C for 30 min in O2 atmosphere were 5.0 µC/cm2 and 80 kV/cm, respectively.

Directly crystallized SrBi2(Ta1-x Nb x )2O9 (SBTN) films were deposited on (111) Pt/Ti/SiO2/Si substrates at 585–670°C by thermal metalorganic chemical vapor deposition (MOCVD). The crystalline SBTN film was directly deposited at 670°C irrespective of the deposition rate, but its leakage current markedly decreased when the deposition rate decreased from 5.0 to 2.1 nm/min. When the deposition rate was below 2.1 nm/min, an SBTN film with large ferroelectricity was deposited even at 585°C, and strong (103)-orientation was ascertained by an X-ray reciprocal space mapping method. This orientation is considered to locally epitaxially occur on a (111)-oriented Pt substrate. Twice the remanent polarization (2P r) and twice the coercive field (2E c) of the film deposited at 585°C were 12.2 µC/cm2 and 160 kV/cm, respectively. When the deposition temperature increased, the film became randomly oriented which was in response to the orientation change in the Pt substrate from single (111) to a mixed orientation of (111) and (100) orientations by heating before starting the film deposition. 2P r and 2E c of the film deposited at 670°C increased to 23.8 µC/cm2 and 190 kV/cm, respectively.