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Microstructural Defects and Their Formation Mechanisms in Ba0.75Sr0.25TiO3 Epitaxial Film

Author(s): LI Chun-Yan, LIU Xue-Hua, DIAO Fei-Yu, LIANG Wen-Shuang, WANG Yi-Qian, PETROV Peter, ALFORD Neil

Journal: Journal of Inorganic Materials
ISSN 1000-324X

Volume: 27;
Issue: 3;
Start page: 285;
Date: 2012;
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Keywords: Ba0.75Sr0.25TiO3 epitaxial film; high-resolution transmission electron microscopy; microstructural defects; formation mechanism

Ba0.75Sr0.25TiO3 film was epitaxially grown on a (001) LaAlO3 substrate using single―target pulsed laser deposition. The microstructure of the epitaxial film was investigated by high―resolution transmission electron microscope (HRTEM), and the formation mechanism of microstructural defects was explored. It was shown that misfit and threading dislocations existed in the epitaxial Ba0.75Sr0.25TiO3 film. Apart from the dislocations, two different kinds of antiphase boundaries, straight and zig―zagged, were observed. For misfit dislocations, they were formed due to the lattice mismatch between LaAlO3 and Ba0.75Sr0.25TiO3 which could dissociate into several partial dislocations. For the threading dislocations, it was found that their dissociation usually coexists with stacking faults. The formation mechanism of the antiphase boundaries is attributed to the terrace or step on the surfaces of LaAlO3 substrate. If the nucleation site is just on the terrace, straight antiphase boundaries will be formed. However, if the nucleation site is not just on the terrace but a little far away from the terrace, zig―zagged antiphase boundaries will be produced. The results could shed light on the microstructural defects in other perovskite epitaxial films.
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