Free-standing and supported phosphorene nanoflakes: Shape- and size-dependent properties

The ultra-small sized nanomaterials are important for basic functional components of future nanoelectronics, spintronics and sensor devices. In this study, based on first-principles density functional theory, the free-standing and supported nanoflakes of bare and hydrogen saturated black and blue phosphorene of diverse size and shape have been investigated. Cohesion, formation energy, thermal stability and electronic structure of these nanoflakes have been revealed. For nanoflakes supported by specific substrates, such as phosphorene, graphene and Mos(2) monolayer, the equilibrium configuration and the binding energy of the flakes, as well as the effects of substrate on the electronic structure have been investigated. While the cohesive and formation energies and HOMO-LUMO gaps of nanoflakes with their edges passivated by hydrogen display clear size, shape and edge geometry dependencies, they are rather dispersed in bare nanoflakes. The binding of phosphorene nanoflakes to two-dimensional (2D) phosphorene, graphene and MoS2 monolayers is generally weak and originate from van der Waals interaction. Accordingly, when supported by these monolayers, the electronic structure of free-standing nanoflakes can be preserved for critical applications.