Optical investigation of epitaxial silicene on Ag(111)

Silicene keeps on attracting the attention of the scientific community due to both its expected fascinating physical properties and its integrability in the present Si-based industry. Despite huge efforts devoted to silicene characterization, a picture of its physical properties is still lacking. The presence of degenerate superstructures together with a local Si-Ag hybridization, makes the valence band structure non-trivial. We elucidate the nature of epitaxial silicene on Ag(111) by means of optical CW and time-resolved techniques supported by ab-initio modelling. Based on Raman spectroscopy we confirm the lattice hexagonal symmetry and determine the electronic character of the different superstructures. We study the ultrafast photophysical properties of silicene via differential transmission spectroscopy. An intense feature in the spectrum, followed by a decay of one picosecond, is observed in the UV spectral region. This feature evidences to the presence of the Si layer and can be ascribed to a Si-Ag coupling, resulting in an enhancement of the Ag surface plasmon.