Blue Phosphorene on Au(111): theory, spectroscopy and diffraction reveal the role of single Au adatoms

In investigating monoatomic layers of P, several stable two-dimensional (2D) allotropes have been theoretically predicted and, amid them, single-layer blue phosphorus (BlueP) seems to deliver promising premises. After a first success, where the structure of BlueP triangular patches on Au(111) was conceived on the basis of Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT), the surface structure model was then revisited more than once, with increasing accuracy and insight of the theoretical calculations and experimental datasets. Interestingly, the quest for a reliable atomic structure model of BlueP on Au(111) turned out to be very debated and challenging, particularly considering the possible incorporation of Au atoms in the 2D sheet of P. This article proposes an extended report on the theoretical findings that can be extracted from DFT calculations of the orbital projected band structure and employed for an efficient comparison protocol between calculations and experimental datasets coming from Angle Resolved Photoelectron Emission Spectroscopy (ARPES). The findings, together with experimental and simulated data from STM imaging and Surface X-Ray Diffraction (SXRD), show a complete way to verify the presence and characterize the stabilizing effect of foreign atoms in 2D materials