Crystallization and Structural Phase Transformation in Sub-100-nm-Thick SrBi2Ta2O9 Thin Film

概要

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Crystal phase and structural properties in sub-100-nm-thick SrBi2Ta2O9 (SBT) thin films deposited on silicon substrates have been quantitatively investigated by X-ray diffraction (XRD) and X-ray reflection (XRR) analyses. The simulation fitting of XRR showed that the density and the surface roughness of the SBT film increased and saturated as the annealing temperature increased, indicating the phase transformation from fluorite to Aurivillius and the grain growth were enhanced by the high-temperature annealing. The SBT film was composed of small crystals of fluorite-type and Bi-layered Aurivillius phase after crystallization at temperatures of 730–785°C for 1 h. When annealing temperature was higher than 800°C, the film crystallized into a single phase of Bi-layered Aurivillius. It was also shown that the average crystal size in the SBT film increased with annealing temperature and saturated to be ${\sim}75$ nm at annealing temperatures higher than 800°C. The annealing temperature dependence of the integrated intensity of the diffraction suggested that the activation energy of the crystallization into the Aurivillius phase was significantly changed at ${\sim}800$°C. The change in the activation energy had a close relationship with the structural phase transformation of fluorite to Aurivillius and the grain growth.
2005-04-15