Jiao Yalong, Ma Fengxian, Gu Jinxing, Chen Zhongfang, Du Aijun
School of Physics and Chemistry and Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia.
Nanoscale. 2020 May 21;12(19):10543-10549. doi: 10.1039/c9nr10774f. Epub 2020 Mar 29.
The successful synthesis of two-dimensional (2D) boron sheets typically relies on the utilization of a silver surface, which acts as a gated substrate compensating for the electron-deficiency of boron. However, how the structures of one-dimensional (1D) boron are affected by the gating effect remains unclear. By means of an unbiased global minimum structure search and density functional theory (DFT) computations, we discovered the coexistence of 2D boron sheets and 1D ribbons triggered by electrostatic gating. Specifically, at a low excess charge density level (<0.1 e per atom), 2D boron sheets dominate the low energy configurations. As the charge density increases (>0.3 e per atom), more 1D boron ribbons emerge, while the number of 2D layers is reduced. Additionally, a number of low-lying 1D boron ribbons were discovered, among which a flat borophene-like ribbon (FBR) was predicted to be stable and possess high mechanical strength. Moreover, the electride CaN was identified as an ideal substrate for the fabrication of the FBR because of its ability to supply a strong electrostatic field. This work bridges the gap between 2D and 1D boron structures, reveals the polymorphism of 1D boron ribbons under the electrostatic gating effect, and in general provides broad implications for future synthesis and applications of low-dimensional boron materials.
二维（2D）硼片的成功合成通常依赖于银表面的利用，银表面作为一种门控衬底，可补偿硼的电子不足。然而，一维（1D）硼的结构如何受到门控效应的影响仍不清楚。通过无偏全局最小结构搜索和密度泛函理论（DFT）计算，我们发现了由静电门控引发的二维硼片和一维带状物的共存。具体而言，在低过量电荷密度水平（<0.1 e/原子）下，二维硼片主导低能量构型。随着电荷密度增加（>0.3 e/原子），出现更多的一维硼带，而二维层的数量减少。此外，还发现了一些低能的一维硼带，其中一种类似硼烯的扁平带（FBR）被预测是稳定的且具有高机械强度。此外，由于其能够提供强静电场，电子化合物CaN被确定为制备FBR的理想衬底。这项工作弥合了二维和一维硼结构之间的差距，揭示了静电门控效应下一维硼带的多态性，并总体上为低维硼材料的未来合成和应用提供了广泛的启示。
