Ferroelectricity is generally deteriorated or even vanishes when the ferroelectric films are downsized to unit cell scale. To maintain and enhance the polarization in nanoscale ferroelectrics are of scientific and technological importance. Here, giant polarization sustainability is reported in a series of ultrathin PbTiO₃ films scaled down to three unit cells grown on NdGaO₃(110) substrates with La_0.7Sr_0.3MnO₃ as bottom electrodes. Atomic mappings via aberration‐corrected scanning transmission electron microscopy demonstrate the robust ferroelectricity for the sub‐10 nm thick film. For the 1.2 nm thick film, the polarization reaches ≈50 µC cm⁻². The 2 nm thick film possesses a polarization as high as the bulk value. The films ranging from 10 to 35 nm display a giant elongation of out‐of‐plane lattice parameter, which corresponds to a polarization of 100 µC cm⁻², 20% larger than that of the bulk PbTiO₃. The giant enhancement of polarization in the present films is proposed to result from the charge transfer at the La_0.7Sr_0.3MnO₃/PbTiO₃ interface, as supported by the anomalous decrease of Mn valence measured from X‐ray photoelectron spectroscopy. These results reveal the significant role of charge transfer at interfaces in improving large polarizations in ultrathin ferroelectrics and are meaningful for the development of future electronic devices.

中文翻译：

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电荷转移稳定的超薄铁电薄膜的极极化可持续性

当将铁电膜减小到单位晶胞尺寸时，铁电通常会劣化甚至消失。维持和增强纳米铁电体中的极化具有科学和技术重要性。在此，报道了一系列超薄的PbTiO ₃薄膜具有极强的极化可持续性，该薄膜可缩小到在以La _0.7 Sr _0.3 MnO ₃为底部电极的NdGaO ₃（110）衬底上生长的三个晶胞。通过像差校正的扫描透射电子显微镜进行的原子映射证明了亚10纳米厚膜的强铁电性。对于1.2 nm厚的薄膜，偏振达到≈50µC cm ^-2。2 nm厚的膜具有高达体值的偏振。范围从10到35 nm的薄膜显示出巨大的面外晶格参数延伸，这对应于100 µC cm ^-2的极化，比本体PbTiO ₃的极化大20％。提出本薄膜中极化的极大增强是由于在La _0.7 Sr _0.3 MnO ₃ / PbTiO ₃处的电荷转移引起的X射线光电子能谱法测得的Mn价异常降低为界面提供了支持。这些结果揭示了界面电荷转移在改善超薄铁电体中的大极化方面的重要作用，对于未来电子设备的开发具有重要意义。