Abstract Strikingly challenging the widely accepted opinion that a giant spontaneous polarization (Ps) of ~150 μC/cm2 in pure BiFeO3 can only be achieved in strain-induced tetragonal(-like) thin films up to a few hundred nm thick, rhombohedral-like, (110)-oriented BiFeO3 thick films (~2 μm) sputter-deposited at 500°C and 450°C exhibit giant Ps values of 152 μC/cm2 and 126 μC/cm2, respectively. Using a thermodynamic computation based on the Landau-Ginzburg-Devonshire potential (LGD) and a density functional theory (DFT) calculation, the enhanced ferroelectric polarization can be qualitatively explained by a (110) growth-orientation and a moderate compressive strain (~ -1.3%). While the (110)-orientation gives a boost in electric polarization by a ratio of ~ 2 as compared to that of (100), and an enhanced piezoelectric response with respect to that of (111), the compressive strain, which is due to a low deposition temperature on Si, further improves the electric polarization and the related piezoelectric response. The resulting large piezoelectric d33 coefficient of ~120 pm/V in the 500°C-deposited film is well correlated with its giant Ps. This work demonstrates how to achieve a large ferroelectric polarization and a high piezoelectric coefficient in bulk-like BiFeO3 films on Si, implying a great potential of this lead-free multiferroic for applications in Si-based integrated devices.

中文翻译：

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菱形 BiFeO3 厚膜集成在 Si 上，具有巨大的电极化和显着的压电性

摘要 引人注目地挑战了广泛接受的观点，即纯 BiFeO3 中~150 μC/cm2 的巨大自发极化 (Ps) 只能在应变诱导的四方（类）薄膜中实现，厚度可达几百纳米，菱面体状, (110) 取向的 BiFeO3 厚膜（~2 μm）在 500°C 和 450°C 下溅射沉积，分别表现出 152 μC/cm2 和 126 μC/cm2 的巨大 Ps 值。使用基于 Landau-Ginzburg-Devonshire 势 (LGD) 的热力学计算和密度泛函理论 (DFT) 计算，可以通过 (110) 生长取向和适度的压缩应变 (~ - 1.3%）。虽然与 (100) 取向相比，(110) 取向使电极化程度提高了 ~ 2，但 并且相对于（111）的压电响应增强，由于Si上的低沉积温度导致的压缩应变进一步改善了电极化和相关的压电响应。在 500°C 沉积膜中产生的~120 pm/V 的大压电 d33 系数与其巨大的 Ps 密切相关。这项工作展示了如何在 Si 上的块状 BiFeO3 薄膜中实现大的铁电极化和高压电系数，这意味着这种无铅多铁性在 Si 基集成器件中的应用具有巨大潜力。在 500°C 沉积膜中产生的~120 pm/V 的大压电 d33 系数与其巨大的 Ps 密切相关。这项工作展示了如何在 Si 上的块状 BiFeO3 薄膜中实现大的铁电极化和高压电系数，这意味着这种无铅多铁性在 Si 基集成器件中的应用具有巨大潜力。在 500°C 沉积薄膜中产生的~120 pm/V 的大压电 d33 系数与其巨大的 Ps 密切相关。这项工作展示了如何在 Si 上的块状 BiFeO3 薄膜中实现大的铁电极化和高压电系数，这意味着这种无铅多铁性在 Si 基集成器件中的应用具有巨大潜力。