Ab initio studies of thermodynamic and electronic properties of phosphorene nanoribbons

Abstract

We present a density functional theory study of the thermodynamic and electronic properties of phosphorene nanoribbons. We consider a variety of terminations and reconstructions of ribbon edges, both with and without hydrogen passivation, and calculate an ab intio phase diagram that identifies energetically preferred edges as a function of temperature and hydrogen partial pressure. These studies are also accompanied by detailed electronic structure calculations from which we find that ribbons with hydrogenated edges are typically direct gap semiconductors with fundamental gaps that are in excess of phosphorene, the gaps varying inversely with ribbon width. In contrast, ribbons with bare or partially passivated edges either have metallic edges or are semiconducting with band gaps that are smaller than those of their hydrogenated counterparts due to the appearance of midgap edge states. Overall, our studies provide a basis for tailoring the electronic properties of phosphorene nanoribbons by controlling the edge termination via processing conditions (temperature and hydrogen partial pressure) as well as by confinement of carriers via control over ribbon width.