Demonstration of the Existence of Dumbbell Silicene: A Stable Two-Dimensional Allotrope of Silicon

We report a combined experimental and theoretical study on the formation of dumbbell silicene structures Ag(110). High-resolution scanning tunneling microscopy (STM) reveals rich tapestry adatom-free -decorated bidimensional phases covering whole Ag(110) surface. The most thermodynamically stable models obtained from density-functional theory (DFT) perfectly reproduce all features observed by STM. These correspond to different Si buckled honeycomb reconstructions ((13 × 4), c(18 c(8 4)) composed two periodic motifs common structural models. DFT calculations show that these are stabilized presence ordered arrays adatoms adsorbed top in configuration. Grazing incidence X-ray diffraction (GIXD) measurements confirm growth layer. structure factor values well reproduced (13 4) model with 4 per unit cell slight distortion hexagonal cell. Our STM-DFT-GIXD demonstrates silicene, theoretically predicted two-dimensional allotrope. This opens up perspectives for tuning peculiar properties silicene.