From √3 × √3 R30°-arsenene to 5 × 5-arsenene on Ag(111): an atomic reversible phase transition

Two dimensional (2D) √3 × √3 R30◦-As, has been discovered on Ag(111)1 × 1 surface, by depositing 1 monolayer of As, keeping the silver substrate at a temperature of ∼450 ◦C, while a 2D 5 × 5 reconstruction, attributed to arsenene, appeared at a lower temperature of ∼350 ◦C. The two √3 × √3 R30◦-As and 5 × 5-arsenene surface reconstructions were experimentally investigated by means of low electron energy diffraction, and Auger electron spectroscopy, while the first-principles calculations, by using density functional theory, confirmed their atomic configurations, surface stability, and the prediction that the √3 × √3 R30◦-As reconstruction, can be considered as a new allotropic form of arsenene, exhibiting electronic structure with metallic character. A reversible structural phase transition, from the 2D √3 × √3 R30◦-arsenene to the 5 × 5-arsenene surface reconstruction, induced by electron-beam irradiation, and recovered to the √3 × √3 R30◦-As, by annealing, was observed, opening a new path to study reversible phase transitions in elemental epitaxial 2D materials.