Probing the Weak Interaction between Silver and Boron

Abstract

Understanding the boron-coinage-metal interactions is critical for understanding the nucleation and growth mechanisms of borophene on coinage-metal substrates. Binary metal-boron clusters provide ideal models for obtaining atomic-level information about the metal-boron interactions. Here we report an investigation of the structure and bonding of the AgB₈⁻ cluster as a model system to gain insight into the interaction of boron with silver, the most inert substrate to grow borophene. Photoelectron spectroscopy reveals that the spectra of AgB₈⁻ resemble those of bare B₈⁻, suggesting extremely weak chemical interactions between Ag and boron. Quantum calculations show that AgB₈⁻ (C_s, ¹A′) consists of a B₈ borozene weakly interacting with a Ag atom on its edge. Chemical bonding analyses find that the Ag atom interacts with the B₈ motif primarily through its 5s orbital with little perturbation to the structure and bonding of the B₈ borozene. Compared to CuB₈⁻ and AuB₈⁻, Ag is found to have the weakest interaction with the B₈ motif, consistent with that fact that silver substrates are the most inert for borophene syntheses.