Ultra-stable metallic freestanding multilayer borophene with tunable work function

This study examines the structural stability of 1-3-layer structures of seven typical borophene classes (alpha, alpha 1, alpha 5, chi 3, beta 12, delta 6, and delta 3), and the results obtained indicate that alpha- and alpha 5-borophene exhibits the top two favorable stability in the 1-3-layer series. Accordingly, the structural stabilities, electronic structures, and work functions of 1-5-layer alpha- and alpha 5-borophene are investigated systematically. The increased binding energies (Eb) with increasing layer number for both alpha- and alpha 5-borophene demonstrate that their stabilities are enhanced, as confirmed by ab initio molecular dynamics simulations. Remarkably, the interlayer bonding of alpha-borophene shifts from the isolated covalent dominant B-B bonds (2-layer) to 5- or 6-centered localized bonds with mixed covalent and ionic components (4-/5-layer), leading to the formation of an unprecedented interconnected 2D tubular geometry (alpha-type boron nanotubes), which significantly enhances the interlayer bonding strength and contributes dominantly to the increasing Eb with increasing layer number. Contrarily, the increased thermodynamic stability for alpha 5-borophene with increasing layer number mainly originates from the increased in-plane bonding interaction. In particular, the highly stable metallic 5-layer alpha 5- (4.54 eV) and alpha-borophene (5.66 eV) structures with favorable work functions are considered alternative material of graphene and highly attractive anode materials for applications in electronic devices, respectively.

Automated summary

This study investigates the structural stability of seven typical borophene classes (alpha, alpha 1, alpha 5, chi 3, beta 12, delta 6, and delta 3) with 1-3 layers. The results show that alpha and alpha 5 borophene exhibit the highest level of stability in the 1-3 layer series. The study also examines the electronic structures and work functions of 1-5 layer alpha and alpha 5 borophene. The findings suggest that alpha type boron nanotubes formed by alpha-borophene enhance interlayer bonding strength and can be used as alternative materials to graphene.