Colossal Strain Tuning of Ferroelectric Transitions in KNbO<sub>3</sub> Thin Films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39533481.
- Also identified by DOI 10.1002/adma.202408664 and PMC identifier 11681320.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Strong coupling between polarization (P) and strain (ɛ) in ferroelectric complex oxides offers unique opportunities to dramatically tune their properties. Here colossal strain tuning of ferroelectricity in epitaxial KNbO<sub>3</sub> thin films grown by sub-oxide molecular beam epitaxy is demonstrated. While bulk KNbO<sub>3</sub> exhibits three ferroelectric transitions and a Curie temperature (T<sub>c</sub>) of ≈676 K, phase-field modeling predicts that a biaxial strain of as little as -0.6% pushes its T<sub>c</sub> > 975 K, its decomposition temperature in air, and for -1.4% strain, to T<sub>c</sub> > 1325 K, its melting point. Furthermore, a strain of -1.5% can stabilize a single phase throughout the entire temperature range of its stability. A combination of temperature-dependent second harmonic generation measurements, synchrotron-based X-ray reciprocal space mapping, ferroelectric measurements, and transmission electron microscopy reveal a single tetragonal phase from 10 K to 975 K, an enhancement of ≈46% in the tetragonal phase remanent polarization (P<sub>r</sub>), and a ≈200% enhancement in its optical second harmonic generation coefficients over bulk values. These properties in a lead-free system, but with properties comparable or superior to lead-based systems, make it an attractive candidate for applications ranging from high-temperature ferroelectric memory to cryogenic temperature quantum computing.