Silicene (Si-ene) represents an ideal 2D material that shares all the outstanding characteristics of graphene (mainly magnetic, mechanical, optical and electrical properties) associated with the additional advantage of a narrow band gap that can easily be opened by doping or by applying external electric and magnetic fields and mechanical strain. It also has the significant potential for straightforward integration into industrial semiconductor production lines, making Si-ene a promising candidate for microelectronic devices. Si-ene has therefore attracted a large amount of studies and has been the subject of intense debates about the origin of the complex surface superstructures observed as well as its strong interaction with the substrate.

Si-ene has been initially discovered on silver substrate paving the way for the achievement of numerous remarkable results. A rapid overview of the growth and properties of Si-ene on Ag system will be reported in the first part of the presentation. 

In the light of these results, many groups started to investigate the growth of Si-ene on various inert substrates. Graphene (Gr), consisting of an inert, thermally stable material with an atomically flat, dangling bond-free surface is by essence an ideal template layer for van der Waals heteroepitaxy of Si-ene. However, depending on the synthesis method and growth parameters, Gr could exhibit various surface configurations (surface structures, thicknesses, defects, steps heights) that noticeably affect the subsequent growth of epitaxial layers. The growth of Si-ene on CVD epitaxial graphene on 6H-SiC substrate will be reported in the second part of the presenttion. 

It will be shown that the perfect control of full-scale defect-free 1 ML Gr associated with ultra-clean MBE deposition of silicon and a very low growth rate represent key prerequisites for ensuring the growth of extended Si-ene sheets on (6x6)Gr/6H-SiC. At low coverages, the deposition of Si produces large silicene sheets (some hundreds of nanometers large) attested by both AFM and SEM observations and the onset of a Raman peak at 560cm-1 very close to the theoretical value of 570cm-1 calculated for free-standing silicene. This vibration mode at 560cm-1 represents the highest ever experimentally measured value and is representative of quasi-free standing Si-ene as expected in the case of almost no interaction with non-metal substrates. From a coverage rate of 1ML, the Si-ene sheets disappear at the expense of 3D Si dendritic islands whose density, size, and thickness increase with the deposited thickness. From this coverage, the Raman mode assigned to quasi-free standing Si-ene totally vanishes, and the 2D flakes of silicene are no longer observed by AFM. The growth modes are explained by kinetic Monte-Carlo simulations that rationalize the initial flake growth in solid-state dewetting conditions, followed by the growth of ridges surrounding and covering the 2D flakes.