a-axis Contribution to the Polarization Value in (117)/(200)-Oriented Bi3.75La0.25Ti3O12 Thin Films Deposited on Pt(111)/Ti/SiO2/Si Substrate

초록

The a-axis contribution to the polarization value in Bi3.75La0.25Ti3O12 (BLT0.25) thin films deposited on Pt (111)/Ti/SiO2/Si was investigated. The films were prepared by using a chemical solution deposition method. In order to examine the internal vibration modes of the BLT0.25 thin films, we employed Raman spectroscopy at room temperature with a 514.5 nm Ar+ laser as the (117) and (200) excitation source. The films annealed at 750 degrees C and 800 degrees C have preferentially orientations and the proportion of grains with those two orientations in the films was estimated from the X-ray peak intensity. The intensity of the (117) peak increases (over 3.5 times) and the peak position is shifted to lower 2 theta angles. largely reflecting in the increases of the number of (117)-oriented grains and in the lattice constant c as the annealing temperature increases. The increase in the lattice constant c can also be supported by the enhancements of the 566 and the 618 cm(-1) Rainan peaks, which demonstrates an enlargement of TiO6 symmetric stretching mode. In addition, the lattice constant a increases from 5.3675 angstrom to 5.3957 angstrom as the annealing temperatures is increased from 750 degrees C to 800 degrees C in spite of the fact that the two polarization curves are quite similar. Thus, the dominant axis contributing to the total polarization value is the a-axis.

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