Phase engineering in NaNbO₃ thin films fabricated by PLD: Strain, substrate and temperature role on the Q FE – P AFE phase transition

Abstract

International audienceThis study explores precise control over ferroelectric (Q) and antiferroelectric (P) phase transitions in NaNbO3 (NNO) thin films, essential for sustainable electronic applications. Epitaxial NNO layers (10–290 nm) were grown via Pulsed Laser Deposition (PLD) onto SrTiO3 (001) and NdGaO3 (110)/(101). X-ray diffraction and reciprocal-space mapping show films deposited at 600 °C nucleate as a fully strained Q phase; beyond a thickness of about 45 nm on NdGaO3, they relax into the P phase. Elevated deposition temperature (750 °C) facilitates early partial relaxation of the Q-phase and promotes nucleation and growth of the P-phase, evident from distinctive morphologies observed by Atomic Force Microscopy (AFM). Conductive AFM further links structural phases to their distinct electrical signatures, showcasing ferroelectric hysteresis in Q-phase regions and more complex loops in P/Q mixed-phase domains. Notably, on NdGaO3 (101), we demonstrate distinct single-phase growth; by selecting deposition temperature, we obtain exclusively the Q or P phase, without mixed states. These results provide insights into controlling structural transitions in NNO thin films, guiding their future development for sustainable electronics, energy storage, piezoelectric microdevices, and multifunctional systems