Linear response and nonlocal dielectric function of freestanding and substrate-supported borophene from first-principles

Two dimensional boron, or borophene, is a metallic monolayer material that has been recently synthesized on metallic substrates. First principles studies on the mechanical, optical, and electronic properties of borophene have predicted novel applications of borophene in flexible and power electronics. Additionally, borophene is a flexible, transparent, metallic material with highly nonlocal and anisotropic permittivity, and is a candidate as a plasmonic material. Here, we utilized first-principles density functional theory to conduct a systematic investigation of the linear response in isolated and metal-supported borophene, in order to quantitatively describe plasmon resonances in the visible region in the presence of the substrate. We determine that the dielectric properties of borophene are significantly affected by a silver substrate. This has implications for monolayer and thin film plasmonic and optoelectronic devices based on this platform.