Imparting α-Borophene with High Work Function by Fluorine Adsorption: A First-Principles Investigation

Increasing the work function of borophene over a large range is crucial for the development of borophene-based anode materials for highly efficient electronic devices. In this study, the effect of fluorine adsorption on the structures and stabilities, particularly on the work function, of α-borophene (BBP), was systematically investigated via first-principles density functional theory. The calculations indicated that BBP was well-stabilized by fluorine adsorption and the work functions of metallic fluorine-adsorbed BBPs (Fn-BBPs) sharply increased with increasing fluorine content. Moreover, the work function of F-BBP was close to that of the frequently used anode material Au and even, for other Fn-BBPs, higher than that of Pt. Furthermore, we have comprehensively discussed the factors, including substrate deformation, charge transfer, induced dipole moment, and Fermi and vacuum energy levels, affecting the improvement of work function. Particularly, we have demonstrated that the charge redistribution of the substrate induced by the bonding interaction between fluorine and the matrix predominantly contributes to the observed increase in the work function. Additionally, the effect of fluorine adsorption on the increase in the work function of BBP was significantly stronger than that of silicene or graphene. Our results concretely support the fact that Fn-BBPs can be extremely attractive anode materials for electronic device applications.