Colossal Strain Tuning of Ferroelectric Transitions in KNbO3 Thin Films

• DOI: 10.1002/adma.202408664
• Publication Date: 2024-11-13T11:35:25Z
• Authors: Sankalpa Hazra; Tobias Schwaigert; Aiden Ross; Haidong Lu; Utkarsh Saha; Victor Trinquet; Betul Akkopru‐Akgun; Benjamin Z. Gregory; Anudeep Mangu; Suchismita Sarker; Tatiana Kuznetsova; Saugata Sarker; Xin Li; Matthew R. Barone; Xiaoshan Xu; John W. Freeland; Roman Engel‐Herbert; Aaron M. Lindenberg; Andrej Singer; Susan Trolier‐McK...; David A. Muller; Gian‐Marco Rignanese; Salva Salmani‐Rezaie; Vladimir A. Stoica; Alexei Gruverman; Long‐Qing Chen; Darrell G. Schlom; Venkatraman Gopalan
• Keywords: Tetragonal crystal system; Strain engineering; Atmospheric temperature range

Abstract Strong coupling between polarization ( P ) and strain (ɛ) in ferroelectric complex oxides offers unique opportunities to dramatically tune their properties. Here colossal tuning of ferroelectricity epitaxial KNbO 3 thin films grown by sub‐oxide molecular beam epitaxy is demonstrated. While bulk exhibits three transitions a Curie temperature T c ≈676 K, phase‐field modeling predicts that biaxial as little −0.6% pushes its > 975 decomposition air, for −1.4% strain, 1325 melting point. Furthermore, −1.5% can stabilize single phase throughout the entire range stability. A combination temperature‐dependent second harmonic generation measurements, synchrotron‐based X‐ray reciprocal space mapping, transmission electron microscopy reveal tetragonal from 10 K an enhancement ≈46% remanent r ), ≈200% optical coefficients over values. These properties lead‐free system, but with comparable or superior lead‐based systems, make it attractive candidate applications ranging high‐temperature memory cryogenic quantum computing.