Metal

Bilayer

Chemical physics

Boron

Metallurgy

Materials science

Graphene

Biochemistry

Acoustics

Substrate (aquarium)

Lattice (music)

Geology

Oceanography

Physics

Nanotechnology

Organic chemistry

Membrane

Bilayer graphene

Optics

Lattice constant

Condensed matter physics

Monolayer

Borophene

Crystallography

Chemistry

Covalent bond

Diffraction

Nano Letters

The lattice structure of monolayer borophene depends sensitively on the substrate yet is metallic independent of the environment. Here, we show that bilayer borophene on Ag(111) shares the same ground state as its freestanding counterpart that becomes semiconducting with an indirect bandgap of 1.13 eV, as evidenced by an extensive structural search based on first-principles calculations. The bilayer structure is composed of two covalently bonded v1/12 boron monolayers that are stacked in an AB mode. The interlayer bonds not only localize electronic states that are otherwise metallic in monolayer borophene but also in part decouple the whole bilayer from the substrate, resulting in a quasi-freestanding system. More relevant is that the predicted bilayer model of a global minimum agrees well with recently synthesized bilayer borophene on Ag(111) in terms of lattice constant, topography, and moiré pattern.

Quasi-Freestanding Bilayer Borophene on Ag(111)