Experimental realization of honeycomb borophene

We report the successful preparation of a purely honeycomb, graphene-like borophene, by using an Al(111) surface as the substrate and molecular beam epitaxy (MBE) growth in ultrahigh vacuum. Scanning tunneling microscopy (STM) images reveal perfect monolayer borophene with planar, non-buckled honeycomb lattice similar as graphene. Theoretical calculations show that the honeycomb borophene on Al (111) is energetically stable. Remarkably, nearly one electron charge is transferred to each boron atom from the Al(111) substrate and stabilizes the honeycomb borophene structure, in contrast to the negligible charge transfer in case of borophene/Ag(111). The existence of honeycomb 2D allotrope is important to the basic understanding of boron chemistry, and it also provides an ideal platform for fabricating boron-based materials with intriguing electronic properties such as Dirac states. (C) 2018 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.