Thickness-Dependent Evolution of Piezoresponses and Stripe 90° Domains in (101)-Oriented Ferroelectric PbTiO3 Thin Films

Yanpeng Feng; Yunlong Tang; Desheng Ma; Yinlian Zhu; Minjie Zou; Mengjiao Han; Jinyuan Ma; Xiuliang Ma

doi:10.1021/acsami.8b07206

Thickness-Dependent Evolution of Piezoresponses and Stripe 90° Domains in (101)-Oriented Ferroelectric PbTiO₃ Thin Films

ACS Appl Mater Interfaces. 2018 Jul 25;10(29):24627-24637. doi: 10.1021/acsami.8b07206. Epub 2018 Jul 11.

Authors

Yanpeng Feng^{1

2}, Yunlong Tang¹, Desheng Ma³, Yinlian Zhu¹, Minjie Zou^{1

4}, Mengjiao Han^{1

2}, Jinyuan Ma^{1

5}, Xiuliang Ma^{1

5}

Affiliations

¹ Shenyang National Laboratory for Materials Science, Institute of Metal Research , Chinese Academy of Sciences , Wenhua Road 72 , 110016 Shenyang , China.
² University of Chinese Academy of Sciences , Yuquan Road 19 , 100049 Beijing , China.
³ School of Physics , Nankai University , Weijin Road 94 , 300071 Tianjin , China.
⁴ School of Material Science and Engineering , University of Science and Technology of China , 230026 Hefei , China.
⁵ School of Materials Sciences and Engineering , Lanzhou University of Technology , Langongping Road 287 , 730050 Lanzhou , China.

PMID: 29969007
DOI: 10.1021/acsami.8b07206

Abstract

High-index ferroelectric films as (101)-orientated ones exhibit enhanced dielectric responses, piezoelectric responses, and exotic ferroelectric switching behaviors, which are potential candidates for applications in memories and capacitors. However, possible domain patterns and domain wall structures in (101)-oriented ferroelectric thin films are still elusive, which results in difficulties in understanding the origin and further modulating their special properties. In this work, a series of PbTiO₃ (PTO) thin films with 35, 50, 60, and 70 nm in thickness were grown on (101)-oriented (LaAlO₃)_0.29(SrTa_1/2Al_1/2O₃)_0.71 (LSAT(101)) substrates by pulsed laser deposition and investigated by both piezoresponse force microscopy (PFM) and (scanning) transmission electron microscopy ((S)TEM). PFM measurements reveal that periodic stripe domains are dominant in 50 nm thick PTO films. Besides stripe domains, a/ c domains appear in films with thickness more than 60 nm. A thickness-dependent evolution of piezoresponse amplitude indicates that the 50 nm thick PTO films demonstrate a superior piezoresponse. Electron diffraction and contrast analysis clarify that all these (101)-oriented PTO films contain periodic stripe ferroelectric 90° domains. The domain periods increase with the film thickness following Kittel's law. Aberration-corrected STEM imaging reveals that the stripe ferroelectric 90° domains have an alternate arrangement of wide and narrow c domains with polarization directions along [100] for c₁ domains and [001̅] for c₂ domains, forming a "head-to-tail" polarization configuration. Further strain analysis reveals that stripe domains have uniform strain distributions and distinct lattice rotations around domain walls. It is proposed that the periodic arrangement of high-density stripe 90° domains in 50 nm thick PTO films is the main contributor to the superior piezoresponse behavior. These results are expected to provide useful information to understand the domain structures in (101)-oriented PTO thin films and thus facilitate further modulation of the properties for potential applications.

Keywords: PbTiO3; TEM; ferroelectric thin films; piezoresponse; stripe 90° domain.