Structural Defects in Sr0. 7Bi2. 3Ta2O9 Thin Film for Ferroelectric Memory

Tetsuya OSAKA  Sachiko ONO  Akira SAKAKIBARA  Ichiro KOIWA  

IEICE TRANSACTIONS on Electronics   Vol.E81-C   No.4   pp.545-551
Publication Date: 1998/04/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Advanced Memory Devices Using High-Dielectric-Constant and Ferroelectric Thin Films)
ferroelectric memory,  structural defects,  Sr0.7Bi2.3Ta2O9 thin film,  TEM observation,  chemical liquid deposition,  

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Using transmission electron microscopy (TEM), we studied structural defects in a Sr0. 7Bi2. 3Ta2O9 (SBT) thin film to be used for ferroelectric memory devices. We examined the effects of the substrate, crystal continuity, and dislocations in crystals as major causes of defects. For this study, we used an SBT thin film grown from an alkoxide solution. Since crystal growth was hardly influenced by the substrate, the substrate had little influence on the occurrence of defects resulted in misfit of lattice constant. Regions of partially low crystal continuity were observed in the SBT thin film. In these regions, the orientation was still uniform, but the continuity of the crystal grain was low because of the defects. In addition, variation in contrast was observed in the crystals, however, no obvious variation in chemical composition was found in this region of varying contrast. Therefore, the contrast variation is considered to be attributed to the dislocation. Such a dislocation was found to be occurred in the direction of the (2010) plane in many instances. The defects in the SBT film were also confirmed by the TEM observation.