Recent synthesis of monolayer borophene (triangle boron monolayer) on the substrate opens the era of boron nanosheet (Science, 350, 1513, $mathbf{2015}$), but the structural stability and novel physical properties are still open issues. Here we demonstrated borophene can be stabilized with fully surface hydrogenation, called as borophane, from first-principles calculations. Most interesting, it shows that borophane has direction-dependent Dirac cones, which are mainly contributed by in-plane emph{p$_{x}$} and emph{p$_{y}$} orbitals of boron atoms. The Dirac fermions possess an ultrahigh Fermi velocity up to 3.0$times$10$^{6}$ m/s, 4 times higher than that of graphene. The Youngs modules are calculated to be 129 and 200 GPa$cdot$nm along two different directions, which is comparable with steel. The ultrahigh Fermi velocity and high mechanical feature render borophane ideal for nanoelectronics applications.
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