Opposite surface stress induced the distinctly different contact behaviors of monolayer and bilayer borophene on Ag(1 1 1)

Abstract

The experimental synthesis of the boron sheets beyond a single layer is a challenge in low-dimensional physics, and the interaction mechanism between multilayered boron sheets and metal substrates remains unclear. Here, we propose an exchange-transfer mechanism to understand the distinctively different behaviors of monolayer (ML) and bilayer (BL) borophene contacts on Ag(111) based on first-principles calculations. It is shown that threefold enhancement of the tensile surface stress in the BL borophene plays a vital role in this exchange-transfer mechanism, while released compressive surface stress was found for ML borophene covers on Ag(111). The feature of the mechanism is that the dz2 electrons on the Ag(111) transferring to the pz orbital of the bridged B pillars are compensated mainly by the electrons from the bottom B px + py orbitals. This mechanism causes more interaction density states between the Ag(111) and BL borophene while not found in the ML borophene. In addition, the analysis of surface stress indicates that it has high feasibility of growing BL borophene by chemical vapor deposition method on Al and Au substrates.