Boron Sheet Adsorbed on Metal Surfaces: Structures and Electronic Properties

Using first-principles calculations based on density functional theory, we studied the possible geometric configurations and electronic structures of three types of monolayer boron sheets (BSs) on different metal (Mg, Al, Ti, Au, and Ag) surfaces. We find that, when adsorbed on metal surfaces, hexagonal BS ( h -BS) is more energy-favorable than triangular BS or mixed hexagonal-triangular BS, and the atop-site adsorption configuration is the most favored. For all h -BS/metal configurations, electrons are observed to transfer from metal to BS, due to the intrinsic electron deficiency of h -BS. Electronic structure analyses show that the substrates could be classified into two types according to the interactions between boron and metal: (1) h -BS on Mg(0001), Al(111), or Ti(0001) shows a relatively larger charge transfer and stronger BS–metal interactions, and the σ (in-plane) bands have the same profile as freestanding h -BS, except for a Fermi level shift caused by the charge transfer. (2) h -BS on Au(111) or Ag(111) surfaces has in-plane bands split into several subbands. A model of coronene on h -BS/Mg(0001) is also investigated, which shows that it is possible to decouple the molecular electronic structure from the metal surface by a buffer of a single sheet of boron.