Solution-based processable high-k 2-dimensional (2D) ferroelectrics have attracted significant interest for use in next-generation nanoelectronics. Although few studies on potential 2D ferroelectric nanosheets in local areas have been conducted, reports on the thin-film characteristics applicable to the device are insufficient. In this study, we successfully synthesize high-k 2D Sr_1.8Bi_0.2Na_n-3Nb_nO_3n+1 (octahedral units, n = 3–5) nanosheets by the engineering of the n of NbO₆ octahedral layers with A-site modification, and realized ferroelectric characteristics in ultrathin films (below 10 nm). The nanosheets are synthesized by a solution-based cation exchange process and deposited using the Langmuir-Blodgett (LB) method. As increasing the NbO₆ octahedral layer, the thickness of the nanosheets increased and the band gaps are tuned to 3.80 eV (n = 3), 3.76 eV (n = 4), and 3.70 eV (n = 5). In addition, the dielectric permittivity of the 5-layer stacked nanofilm increase to 26 (n = 3), 33 (n = 4), and 62 (n = 5). In particular, the increased perovskite layer exhibits large distortions due to the size mismatch of Sr/Bi/Na ions at the A-site and promotes local ferroelectric instability due to its spontaneous polarization along the c-axis caused by an odd n number. We investigate the stable ferroelectricity in Pt/ 5-layer Sr_1.8Bi_0.2Na₂Nb₅O₁₆ / Nb:STO capacitor by polarization-electric field (P-E) hysteresis; the coercive electric field (E_c) was 338 kV cm⁻¹ and the remnant polarization (P_r) 2.36 μC cm⁻². The ferroelectric properties of ultrathin 2D materials could drive interesting innovations in next-generation electronics.

基于溶液的可加工高 k 二维 (2D) 铁电体在下一代纳米电子学中的应用引起了人们的极大兴趣。尽管对局部地区潜在的二维铁电纳米片的研究很少，但适用于该器件的薄膜特性的报道还不够。在本研究中，我们通过对NbO _6的n进行工程化，成功合成了高k 2D Sr _1.8 Bi _0.2 Na _n-3 Nb _n O _3n+1（八面体单元，n  = 3–5）纳米片。A位修饰的八面体层，并在超薄膜（10 nm以下）中实现了铁电特性。纳米片通过基于溶液的阳离子交换过程合成，并使用 Langmuir-Blodgett (LB) 方法沉积。随着NbO ₆八面体层数的增加，纳米片的厚度增加，带隙调整为3.80 eV（n  = 3）、3.76 eV（n  = 4）和3.70 eV（n  = 5）。此外，5层堆叠纳米膜的介电常数增加至26（n  = 3）、33（n  = 4）和62（n = 5）。特别是，由于A位处Sr/Bi/Na离子的尺寸不匹配，增加的钙钛矿层表现出较大的畸变，并且由于奇数n数引起的沿c轴的自发极化而促进局部铁电不稳定性。我们通过极化电场（PE）磁滞研究了Pt/ 5层Sr _1.8 Bi _0.2 Na ₂ Nb ₅ O _{16 / Nb:STO电容器的稳定铁电性；}矫顽电场（E _c）为338 kV cm ^-1，剩余极化（P _r）为2.36 μC cm ^-2。超薄二维材料的铁电特性可以推动下一代电子产品的有趣创新。