Polarization Rotation and Coarsened Domains in Freestanding PbTiO<sub>3</sub> Film with Substantially Enhanced Intrinsic Piezoelectricity Compared to Clamped One.
basic_science · Level V
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- Record sourced from PubMed, PMID 40600775.
- Also identified by DOI 10.1021/acs.nanolett.5c01925.
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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 PbTiO<sub>3</sub> (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 Sr<sub>3</sub>Al<sub>2</sub>O<sub>6</sub>/SrTiO<sub>3</sub> (SAO/STO) substrate, with ferroelectric <i>c</i>-domains coarsened significantly accompanied by notable polarization rotation and vanishing <i>a</i>-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.