We investigate the piezoelectric and ferroelectric properties in island-like ferroelectric regions of bismuth ferrite oxide films. Samples were synthesized by the simultaneous laser ablation of bismuth, and iron oxide targets. Bismuth content in the deposited films was controlled with the plasma density (N_p) that is produced during the ablation of the Bi target. A change in the N_pBi alters the Bi incorporation into the films. Relatively homogeneous films deposited at N_pBi of 11×10¹² cm^-3 with an effective piezoelectric coefficient (d_eff) of ~15 pm/V served as the starting point. A reduction of N_pBi at 2×10¹² cm^-3 produced films with almost null piezoelectrical response but at 4×10¹² cm^-3 caused the formation of island-like ferroelectric regions with large d_eff values that spans from 70 to 108 pm/V. The island-like regions presented upright hysteretic phase-switching loops with low coercive voltages and squareness values close to unity. The resulting large d_eff values were attributed to the reduction of the substrate-clamping effect, the (001)-textured BiFeO₃ structure and the coexistence of secondary phases with the main BiFeO₃ phase. The mechanisms for polarization switching and the electromechanical response of the island-like regions are discussed. Finally, some preliminary results of ferroelectric fatigue experiments in island-like regions are presented.

我们研究了铋铁氧体氧化物薄膜岛状铁电区的压电和铁电特性。通过同时激光烧蚀铋和氧化铁靶来合成样品。沉积膜中的铋含量由在铋靶材烧蚀过程中产生的等离子体密度 ( N _p )控制。N _{pBi 的}变化会改变 Bi 掺入薄膜中。以11×10 ¹² cm ^{-3 的}N _pBi沉积具有~15 pm/V的有效压电系数( d _eff ) 的相对均匀的薄膜作为起点。减少N _pBi在 2×10 ¹² cm ^-3产生的薄膜几乎为零压电响应，但在 4×10 ¹² cm ^-3导致形成岛状铁电区，具有大的d _eff值，范围从 70 到 108  pm/V。岛状区域呈现具有低矫顽电压和接近统一的矩形值的直立滞后相位切换回路。产生的大d _eff值归因于衬底夹持效应的降低、(001) 织构的BiFeO ₃结构以及次级相与主要 BiFeO ₃的共存阶段。讨论了极化转换机制和岛状区域的机电响应。最后，介绍了岛状区域铁电疲劳实验的一些初步结果。