Germanene: a novel two-dimensional germanium allotrope akin to graphene and silicene

Abstract

We have grown an atom-thin, ordered, two-dimensional multi-phase film in situ through germanium molecular beam epitaxy using a gold (111) surface as a substrate. Its growth is similar to the formation of silicene layers on silver (111) templates. One of the phases, forming large domains, as observed in scanning tunneling microscopy, shows a clear, nearly flat, honeycomb structure. Thanks to thorough synchrotron radiation core-level spectroscopy measurements and advanced density functional theory calculations we can identify it as a root 3 x root 3 R(30 degrees) germanene layer in conjunction with a root 7 x root 7 R(19.1 degrees) Au(111) supercell, presenting compelling evidence of the synthesis of the germanium-based cousin of graphene on gold.Drs F Cheynis, D Chiappe, A Ranguis and A Resta are warmly acknowledged for their contributions to the measurements. We are grateful to Dr M Radovic and Dr R S Dhaka at Swiss Light Source and I Vobornik at the Italian synchrotron radiation source Elettra, whose outstanding efforts made these experiments possible. Funding from the 2D-NANOLATTICES project within the 7th Framework Programme for Research of the European Commission, under FET-Open grant number 270749 is greatly appreciated. We acknowledge support from the European Research Council Advanced Grant DYNamo (ERC-2010-AdG-267374), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT-578-13) and European Commission project CRONOS (grant number 280879-2