Giant polarization in super-tetragonal thin films through interphase strain

• Published in: Science (American Association for the Advancement of Science) Vol. 361; no. 6401; pp. 494 - 497
• Main Authors: Zhang, Linxing, Chen, Jun, Fan, Longlong, Diéguez, Oswaldo, Cao, Jiangli, Pan, Zhao, Wang, Yilin, Wang, Jinguo, Kim, Moon, Deng, Shiqing, Wang, Jiaou, Wang, Huanhua, Deng, Jinxia, Yu, Ranbo, Scott, James F., Xing, Xianran
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 03.08.2018
• Subjects: Electric polarization; Epitaxial growth; Ferroelectric materials; Ferroelectricity; Interphase; Lattice matching; Lattice parameters; Lead titanates; Magnetism; Material properties; Metals; Physical properties; Polarization; Thin films; Transition temperature; Transition temperatures
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.aan2433

Strain can have a dramatic effect on the properties of materials. Zhang et al. introduced a large strain in the material PbTiO 3 by growing it epitaxially in a composite with PbO. On the boundaries between the two materials, their normally different lattice constants were matched, giving rise to the strain. As a consequence, the films exhibited a very large electric polarization even in the absence of an electric field. The method may be applicable to generating other functional materials. Scence , this issue p. 494 Epitaxial growth of PbTiO 3 /PbO composite thin films gives rise to strain and a very large spontaneous polarization. Strain engineering has emerged as a powerful tool to enhance the performance of known functional materials. Here we demonstrate a general and practical method to obtain super-tetragonality and giant polarization using interphase strain. We use this method to create an out-of-plane–to–in-plane lattice parameter ratio of 1.238 in epitaxial composite thin films of tetragonal lead titanate (PbTiO 3 ), compared to 1.065 in bulk. These thin films with super-tetragonal structure possess a giant remanent polarization, 236.3 microcoulombs per square centimeter, which is almost twice the value of known ferroelectrics. The super-tetragonal phase is stable up to 725°C, compared to the bulk transition temperature of 490°C. The interphase-strain approach could enhance the physical properties of other functional materials.