Nanotechnology

Organic chemistry

Borophene

Boron

Crystallography

Crystal structure

Chemical physics

Chemistry

Materials science

Monolayer

Nature Chemistry

Borophene, a crystalline monolayer boron sheet, has been predicted to adopt a variety of structures—owing to its high polymorphism—that may possess physical properties that could serve in flexible electronics, energy storage and catalysis. Several borophene polymorphs have been synthesized on noble metal surfaces but for device fabrication larger single-crystal domains are typically needed with, ideally, weak borophene–substrate interactions. Here we report the synthesis of borophene on a square-lattice Cu(100) surface and show that incommensurate coordination reduces the borophene–substrate interactions and also leads to a borophene polymorph different from those previous reported. Micrometre-scale single-crystal domains formed as isolated faceted islands or merged together to achieve full monolayer coverage. The crystal structure of this phase has ten boron atoms and two hexagonal vacancies in its unit cell. First-principles calculations indicate that charge transfer, rather than covalent bonding, binds this two-dimensional boron to the Cu(100) surface. The electronic band structure of this material features multiple anisotropic tilted Dirac cones.                                                                  Borophene, a two-dimensional boron sheet, can adopt a variety of polymorphic structures that are predicted to possess interesting and potentially useful electronic properties. Micrometre-scale single-crystal borophene domains have now been grown on a square-lattice Cu(100) surface. The resulting boron sheets feature a rectangular unit cell, intrinsic stripe modulations and an unusual electron band structure.

Micrometre-scale single-crystalline borophene on a square-lattice Cu(100) surface