Polarization Rotation and Coarsened Domains in Freestanding PbTiO3 Film with Substantially Enhanced Intrinsic Piezoelectricity Compared to Clamped One

Guangtong Yuan; Zhihan Zou; Dirui Wu; Shiyao Xu; Longji Lyu; Yuan Zhang; Boyuan Huang; Changjian Li; Jiangyu Li

doi:10.1021/acs.nanolett.5c01925

Polarization Rotation and Coarsened Domains in Freestanding PbTiO₃ Film with Substantially Enhanced Intrinsic Piezoelectricity Compared to Clamped One

Nano Lett. 2025 Jul 2. doi: 10.1021/acs.nanolett.5c01925. Online ahead of print.

Authors

Guangtong Yuan^{1

2}, Zhihan Zou^{1

2}, Dirui Wu^{1

2}, Shiyao Xu^{1

2}, Longji Lyu^{1

2}, Yuan Zhang^{1

2}, Boyuan Huang^{1

2}, Changjian Li^{1

2}, Jiangyu Li^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China.
² Guangdong Provincial Key Laboratory of Functional Oxide Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China.

PMID: 40600775
DOI: 10.1021/acs.nanolett.5c01925

Abstract

Applications of ferroelectric films critically depend on their polar ordering, which is highly sensitive to the film size and substrate constraint. Previous studies have revealed a much enhanced piezoresponse in ferroelectric nanoislands relaxed from substrate clamping, yet the proposed mechanisms were completely opposite. We revisit this problem utilizing clamped epitaxial and freestanding PbTiO₃ (PTO) films as our model system for systematic investigation via scanning transmission electron microscopy, piezoresponse force microscopy, and second harmonic generation. It is found that freestanding PTO exhibits 97% higher atomic-scale polar displacement compared to the one clamped on the Sr₃Al₂O₆/SrTiO₃ (SAO/STO) substrate, with ferroelectric c-domains coarsened significantly accompanied by notable polarization rotation and vanishing a-domains. These structural changes yield 141% enhancement in the effective piezoelectric coefficient and 404% increase in second harmonic generation intensity for freestanding PTO compared to its epitaxial counterpart clamped by SAO/STO substrate, highlighting the important influence of substrate constraint on ferroelectric films.

Keywords: Freestanding film; PbTiO3; Piezoelectricity; Polar topology.