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

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This study explores precise control over ferroelectric (Q) and antiferroelectric (P) phase transitions in NaNbO 3 (NNO) thin films, essential for sustainable electronic applications. Epitaxial NNO layers (10–290 nm) were grown via Pulsed Laser Deposition (PLD) onto SrTiO 3 (001) and NdGaO 3 (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 NdGaO 3 , 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 NdGaO 3 (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. • Q→P transition in NNO films at 600 °C occurs between 16 and 45 nm on NGO(110) • On NGO (101), temperature enables pure Q or pure P films growth • At 750°C Q relaxes faster and P nucleates giving unique AFM textures on NGO and STO • c-AFM reveals local I–V behavior in Q and P regions below and above 125 nm on STO • Raman and EIS confirm macroscopic FE and AFE below and above the given thresholds