Hydrogen-assisted growth of single crystalline borophene investigated by first-principles calculations

Abstract

The development of an effective method for mass production of single crystalline two-dimensional (2D) materials is still a standing challenge. Here, using first-principles calculations, we predict the crucial role of the simplest and the most abundant element in the universe, hydrogen, as a surfactant in mass production of single crystalline borophene grown on Ag(111). Specifically, hydrogen not only readily induces the dissolved B atoms to segregate onto the Ag(111) substrate, but also promotes the B atoms to fast nucleate via changing the repulsive pairwise interactions of B atoms to be attractive. Importantly, the introduction of a small amount of hydrogen saturation on the edges (the H/B ratio is lower than 1 : 6) effectively lifts the degeneracy of the baby-islands between two most stable borophene phases that are experimentally fabricated, effectively promoting single crystalline growth, via distinct minimization of their edge energies as rationalized by the generalized Wulff construction. The present findings may open a new avenue toward mass production of borophene and other single crystalline 2D materials, and the hydrogen passivation on the edges may facilitate the exfoliation of borophene grown on metal substrates and thus promote the subsequent characterization or applications.