Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208, USA.
Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA.
Science. 2021 Mar 12;371(6534):1143-1148. doi: 10.1126/science.abg1874.
Synthetic two-dimensional polymorphs of boron, or borophene, have attracted attention because of their anisotropic metallicity, correlated-electron phenomena, and diverse superlattice structures. Although borophene heterostructures have been realized, ordered chemical modification of borophene has not yet been reported. Here, we synthesize "borophane" polymorphs by hydrogenating borophene with atomic hydrogen in ultrahigh vacuum. Through atomic-scale imaging, spectroscopy, and first-principles calculations, the most prevalent borophane polymorph is shown to possess a combination of two-center-two-electron boron-hydrogen and three-center-two-electron boron-hydrogen-boron bonds. Borophane polymorphs are metallic with modified local work functions and can be reversibly returned to pristine borophene through thermal desorption of hydrogen. Hydrogenation also provides chemical passivation because borophane reduces oxidation rates by more than two orders of magnitude after ambient exposure.
合成二维硼的同素异形体，即硼烯，因其各向异性的金属性、关联电子现象和多样的超晶格结构而受到关注。尽管已经实现了硼烯异质结构，但尚未有报道对硼烯进行有序的化学修饰。在这里，我们通过原子氢在超高真空环境下对硼烯进行氢化，合成了“硼烷”同素异形体。通过原子尺度成像、光谱和第一性原理计算，最常见的硼烷同素异形体被证明具有二中心二电子硼-氢键和三中心二电子硼-氢键-硼键的组合。硼烷同素异形体具有金属性，局部功函数得到了修饰，并且可以通过热脱附氢气可逆地回到原始的硼烯。氢化还提供了化学钝化作用，因为硼烷在暴露于环境后氧化速率降低了两个数量级以上。
