Two-dimensional blue phosphorene grown on Au(111) by molecular-beam epitaxy*

Single layer (SL) phosphorus (phosphorene) has drawn considerable research attention recently. It is a semiconductor showing superior transport and optical properties. In the past several years, few-layer or SL black phosphorus has been successfully isolated by exfoliation and extensively studied for the electronic and optical properties. Blue phosphorus (blueP), an allotrope of black phosphorus but with a more flat atom arrangement, has been predicted to stabilize in the SL form on some substrates. In this work, we report the growth of blueP by molecular-beam epitaxy and reveal an explicit sequential growth behavior involving a dewetting process. The adsorbed P atoms aggregate into one-dimensional (1D) chains, then (√3×√3)R30^○ patches and finally SL blueP-like islands. Over a large coverage range, a composite surface consisted of locally high-P coverage blueP islands and locally low-coverage 1D chains or loose (√3×√3)R30^○ patches prevails owing to the minimization of the overall system energy.