Atomic structure of the √3 × √3 phase of silicene on Ag(111)

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The growth of the √3 × √3 reconstructed silicene on Ag substrate has been frequently observed in experiments while its atomic structure and formation mechanism is poorly understood. Here, by first-principles calculations, we show that √3 × √3 reconstructed silicene is constituted by dumbbell units of Si atoms arranged in a honeycomb pattern. Our model shows excellent agreement with the experimentally reported lattice constant and STM image. We propose a new mechanism for explaining the spontaneous and consequential formation of √3 × √3 structures from 3×3 structures on Ag substrate. We show that the √3 × √3 reconstruction is mainly determined by the interaction between Si atoms and have weak influence from Ag substrate. The proposed mechanism opens the path to understanding of multilayer silicon
S.C. and A.R. acknowledge financial support from the Marie Curie Grant FP7-PEOPLE-2013-IEF project ID 628876, the European Research Council Advanced Grant DYNamo (ERC-2010-AdG-267374), Spanish Grant (FIS2010-21282-C02-01), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13), Ikerbasque and the European Commission projects CRONOS (Grant No. 280879-2). V.O.O. and S.C. acknowledge the support from TUBA.