Misfit strain relaxations of (101)-oriented ferroelectric PbTiO 3 /(La, Sr)(Al, Ta)O 3 thin film systems
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ARTICLE Misfit strain relaxations of (101)-oriented ferroelectric PbTiO3/(La, Sr)(Al, Ta)O3 thin film systems Yanpeng Feng Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; and University of Chinese, Academy of Sciences, Beijing 100049, China
Yunlong Tang and Yinlian Zhua) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Minjie Zou Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; and School of Material Science and Engineering, University of Science and Technology of China, Hefei 230026, China
Xiuliang Ma Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; and State Key Lab of Advanced Processing and Recycling on Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China (Received 30 July 2018; accepted 19 October 2018)
High-index ferroelectric thin films show excellent dielectricity, piezoelectricity and switching behaviors. Understanding the misfit strain relaxation behavior may prove beneficial to gaining insights into the high-quality growth of high-index ferroelectric films. In this study, ferroelectric PbTiO3 thin films were deposited on the (101)-oriented (La, Sr)(Al, Ta)O3 substrate by pulsed laser deposition and were investigated using (scanning) transmission electron microscopy. Two types of misfit dislocations with line directions of h111i and [010] were found at the interface. The h111i dislocation exhibited Burgers vectors of a[011] or a½011, while the [010] dislocation featured Burgers vectors of a½101. The former might be generated by gliding, and the latter by climbing. We propose that the misfit strain relaxation in this film system basically results from the formation of dislocations and the residual misfit strain is relaxed via the formation of 90° ac domains.
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.422
when the film thickness exceeds the critical value in epitaxial thin films and then reduce the strain tuning ability of substrates.12 Besides, the threading dislocations in films are known to increase the surface roughness of thin films. Nevertheless, a recent study using phase-field simulations demonstrated a beneficial phenomenon that the proper dislocation intensity can reduce the coercive field and meanwhile enhance the remanent polarization of a ferroelectric single crystal.13 Experimentally, a periodic interfacial MD array in a BiFeO3/LaAlO3(001) nanostructure results in a giant strain gradient and consequently enhances the visible light absorption property.14 All these studies indicate that the effects of dislocations on physical properties of perovskite oxide thin films are not clarified so far. Thus, it is essential to systematically investigate the configuration of interfacial MDs and misfit strain relaxati
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