Formation of silicene on silver: Strong interaction between Ag and Si
Résumé
The real-time formation of Si single layers on Ag(110) and Ag(111) has been investigated at different temperatures, by a combination of scanning tunnelling microscopy, grazing incidence X-ray diffraction, optical differential reflectance spectroscopy and density functional theory. It is shown that the reactivity of the Ag substrate with the Si atoms is important. The formation of Si nanoribbons on Ag(110) is accompanied by a missing-row reconstruction of the Ag surface, and the removed Ag atoms form additional islands. The mechanism of Si island formation on Ag(111) involves the insertion of single Si atoms within the Ag top layer and the exchange with Ag atoms. The released Ag atoms diffuse to steps edges and form new Ag fingers. This strong interaction between Si and Ag atoms with possible alloying, questions the actual structures of the different Si phases observed on Ag(110) and Ag(111), and usually attributed to silicene single layers.