Controlling placement of quantum states in phosphorene nanoribbons using ligands

Abstract

The band gap energy and placement of band edges are essential characteristics of a semiconductor. In phosphorene nanoribbons, we show how the placement of terminal ligands and the deposition of alkali atoms on the surface controls these features. We first demonstrate how terminal groups, NH2, OH, H, SCH3, SH, Cl, and OCN, can affect the work function. A significant change in the work function is found that is caused by band bending of the induced dipole of the terminal groups. The dipole was often caused by the ligand itself rather than charge transfer between the ligand and phosphorene. The band gap was tuned by adding alkali atoms on the surface with various concentrations lowering the band gap energy until the material becomes metallic. Our results demonstrate how the band gap energy and the work function may be manipulated in a controlled way either through edge termination or via alkali metals.