Emerging functionalities in two-dimensional materials, such as ferromagnetism, superconductivity and ferroelectricity, open new avenues for promising nanoelectronic applications. Here, we report the discovery of intrinsic in-plane room-temperature ferroelectricity in two-dimensional Bi₂TeO₅ grown by chemical vapor deposition, where spontaneous polarization originates from Bi column displacements. We found an intercalated buffer layer consist of mixed Bi/Te column as 180° domain wall which enables facile polarized domain engineering, including continuously tunable domain width by pinning different concentration of buffer layers, and even ferroelectric-antiferroelectric phase transition when the polarization unit is pinned down to single atomic column. More interestingly, the intercalated Bi/Te buffer layer can interconvert to polarized Bi columns which end up with series terraced domain walls and unusual fan-shaped ferroelectric domain. The buffer layer induced size and shape tunable ferroelectric domain in two-dimensional Bi₂TeO₅ offer insights into the manipulation of functionalities in van der Waals materials for future nanoelectronics.

二维材料的新兴功能，例如铁磁性、超导性和铁电性，为有前景的纳米电子应用开辟了新途径。在这里，我们报告了通过化学气相沉积生长的二维 Bi ₂ TeO ₅中固有的面内室温铁电性的发现，其中自发极化源于 Bi 柱位移。我们发现由混合 Bi/Te 柱组成的插层缓冲层作为 180° 畴壁，可实现轻松的极化畴工程，包括通过钉扎不同浓度的缓冲层来连续可调畴宽度，甚至当极化单元为固定到单个原子列。更有趣的是，插层的 Bi/Te 缓冲层可以相互转化为极化 Bi 柱，最终形成串联阶梯状畴壁和不寻常的扇形铁电畴。二维 Bi ₂ TeO ₅中的缓冲层诱导的尺寸和形状可调铁电域为未来纳米电子学中范德华材料的功能操控提供了见解。