Chen Caiyun, Lv Haifeng, Zhang Ping, Zhuo Zhiwen, Wang Yu, Ma Chen, Li Wenbin, Wang Xuguang, Feng Baojie, Cheng Peng, Wu Xiaojun, Wu Kehui, Chen Lan
Institute of Physics, Chinese Academy of Sciences, Beijing, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
Nat Chem. 2022 Jan;14(1):25-31. doi: 10.1038/s41557-021-00813-z. Epub 2021 Nov 11.
As the nearest-neighbour element to carbon, boron is theoretically predicted to have a planar two-dimensional form, named borophene, with novel properties, such as Dirac fermions and superconductivity. Several polymorphs of monolayer borophene have been grown on metal surfaces, yet thicker bilayer and few-layer nanosheets remain elusive. Here we report the synthesis of large-size, single-crystalline bilayer borophene on the Cu(111) surface by molecular beam epitaxy. Combining scanning tunnelling microscopy and first-principles calculations, we show that bilayer borophene consists of two stacked monolayers that are held together by covalent interlayer boron-boron bonding, and each monolayer has β-like structures with zigzag rows. The formation of a bilayer is associated with a large transfer and redistribution of charge in the first boron layer on Cu(111), which provides additional electrons for the bonding of additional boron atoms, enabling the growth of the second layer. The bilayer borophene is shown to possess metallic character, and be less prone to being oxidized than its monolayer counterparts.
作为与碳最近邻的元素，理论预测硼具有一种平面二维形式，称为硼烯，具有诸如狄拉克费米子和超导性等新奇特性。单层硼烯的几种多晶型物已在金属表面生长出来，但更厚的双层和少层纳米片仍然难以获得。在此，我们报告通过分子束外延在Cu(111)表面合成了大尺寸、单晶双层硼烯。结合扫描隧道显微镜和第一性原理计算，我们表明双层硼烯由两个堆叠的单层组成，它们通过共价层间硼 - 硼键结合在一起，并且每个单层都具有带有锯齿形行的β样结构。双层的形成与Cu(111)上第一个硼层中电荷的大量转移和重新分布相关，这为额外硼原子的键合提供了额外电子，从而使第二层得以生长。双层硼烯显示出具有金属特性，并且比其单层对应物更不易被氧化。
