Two-dimensional borophane semiconductor: a first-principles calculation

The experimentally synthesized graphene-type boron single layer (g-borophene) and its hydrogenated derivative (borophane in Cmmm symmetry) have been confirmed as normal metals, which are not appropriate for applications in the semiconductor field. Based on first-principles calculations, a new adsorption pattern (P6/mmm) with semiconducting feature has been proposed as a metastable phase for hydrogenated borophene. The results show that P6/mmm phase is both dynamically and mechanically stable. Its total energy is 4.829 eV atom-1, which is slightly higher than that of the ground state Cmmm configuration (4.858 eV atom-1). The HSE06-based band structures show that P6/mmm phase is a semiconductor with an indirect band gap of 1.86 eV and such a band gap can be effectively modulated by external strains. Our work shows that surface hydrogenation has the opportunity to induce a metal-insulator transition in two-dimensional borophene and provide a new two-dimensional semiconductor for potential applications in nano-electronic devices.