Electronic Bandgap and Edge Reconstruction in Phosphorene Materials

Abstract

Single-layer black phosphorous (BP), or phosphorene, is a highly-anisotropic two-dimensional elemental material possessing promising semiconductor properties for flexible electronics. However, the direct bandgap of single-layer black phosphorus predicted theoretically has not been directly measured, and the properties of its edges have not been considered in detail. Here we report atomic scale electronic variation related to strain-induced anisotropic deformation of the puckered honeycomb structure of freshly cleaved black phosphorus using a highresolved scanning tunneling spectroscopy (STS) survey along the light (x) and heavy (y) effective mass directions. Through a combination of STS measurements and first-principles calculations, a model for edge reconstruction is also determined. The reconstruction is shown to self-passivate any dangling bond by switching the oxidation state of phosphorous from +3 to +5.