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<p>The development of high-performance lead-free ferroelectric capacitors is critical for the advancement of modern power electronics. This study systematically investigates the thickness-dependent structural and functional properties of epitaxial Ba<sub>0.6</sub>Sr<sub>0.4</sub>TiO<sub>3</sub> films (100–250&#xa0;nm) grown on La<sub>0.5</sub>Sr<sub>0.5</sub>CoO<sub>3</sub> buffered LaAlO<sub>3</sub> (001) substrates. X-ray diffraction analysis confirms a decrease in the out-of-plane lattice parameter and progressive relaxation of the in-plane compressive strain with increasing thickness. Atomic force microscopy shows a reduction in the root-mean-square roughness from 1.931 to 1.108&#xa0;nm as the film thickness increases. Piezoresponse force microscopy reveals consistent nanodomain structures across all thicknesses. Electrically, the leakage current density significantly decreases with increasing film thickness from 3.93 × 10<sup>–4</sup> to 2.02 × 10<sup>–6</sup> A/cm<sup>2</sup> at 500&#xa0;kV/cm. The leakage mechanism has been proven to be Ohmic conduction at low fields, whereas at high fields, a mixed mechanism involving competition between Schottky emission and space-charge-limited-current dominates regardless of film thickness. The Rayleigh coefficients for the real and imaginary parts of the dielectric constant increase substantially (from 0.001 to 0.239&#xa0;cm/kV and 0.011 to 0.041&#xa0;cm/kV, respectively), indicating enhanced domain wall mobility. This enhancement leads to improved tunability (~ 73.73%), reduced coercive field (~ 82.4&#xa0;kV/cm), enhanced breakdown strength (~ 2600&#xa0;kV/cm), and high recoverable energy density and efficiency (~ 22.58&#xa0;J/cm<sup>3</sup> and 64.73% at 2400&#xa0;kV/cm, respectively) in the 250-nm-thick film, which also exhibits excellent frequency (1–100&#xa0;kHz) and thermal (25–120&#xa0;°C) stability. This study establishes domain wall engineering via thickness control as a vital strategy for optimizing lead-free ferroelectric energy storage materials.</p>

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Thickness-driven microstructure evolution and domain wall enhanced energy storage in epitaxial Ba0.6Sr0.4TiO3 ferroelectric films

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Xiangui Zhang,
  • Wencheng Li,
  • Shixi Yu,
  • Xiaoyu Fan,
  • Xuzhe Wang,
  • Haoyang Li,
  • Jianmin Song,
  • Xiaohong Li,
  • Xiangyi Zhang

摘要

The development of high-performance lead-free ferroelectric capacitors is critical for the advancement of modern power electronics. This study systematically investigates the thickness-dependent structural and functional properties of epitaxial Ba0.6Sr0.4TiO3 films (100–250 nm) grown on La0.5Sr0.5CoO3 buffered LaAlO3 (001) substrates. X-ray diffraction analysis confirms a decrease in the out-of-plane lattice parameter and progressive relaxation of the in-plane compressive strain with increasing thickness. Atomic force microscopy shows a reduction in the root-mean-square roughness from 1.931 to 1.108 nm as the film thickness increases. Piezoresponse force microscopy reveals consistent nanodomain structures across all thicknesses. Electrically, the leakage current density significantly decreases with increasing film thickness from 3.93 × 10–4 to 2.02 × 10–6 A/cm2 at 500 kV/cm. The leakage mechanism has been proven to be Ohmic conduction at low fields, whereas at high fields, a mixed mechanism involving competition between Schottky emission and space-charge-limited-current dominates regardless of film thickness. The Rayleigh coefficients for the real and imaginary parts of the dielectric constant increase substantially (from 0.001 to 0.239 cm/kV and 0.011 to 0.041 cm/kV, respectively), indicating enhanced domain wall mobility. This enhancement leads to improved tunability (~ 73.73%), reduced coercive field (~ 82.4 kV/cm), enhanced breakdown strength (~ 2600 kV/cm), and high recoverable energy density and efficiency (~ 22.58 J/cm3 and 64.73% at 2400 kV/cm, respectively) in the 250-nm-thick film, which also exhibits excellent frequency (1–100 kHz) and thermal (25–120 °C) stability. This study establishes domain wall engineering via thickness control as a vital strategy for optimizing lead-free ferroelectric energy storage materials.