Growth of Si ultrathin films on silver surfaces: Evidence of an Ag(110) reconstruction induced by Si

Large differences in the optical properties of a single layer of Si on Ag(110) compared to silicene

“…This is in line with the recent questioning about the silicene nature of the Si NRs grown on Ag(110) [7][8][9].…”

“…On the contrary, no change of slope at any coverage is present at 4.6 eV, and only a tiny effect is seen at 2.0 eV, at the light energies where the main optical features of silicene should be observed. The almost linear evolution of the signal for 2.7 and 3.83 eV up to 1 FC can be associated with the known formation of the NRs at 450 K [7]: for coverages below saturation, very long NRs form on the surface, whose number increases with the Si coverage. Most of them are double NRs, and some are self-assembled, forming local ×2 areas.…”

“…Because of the anisotropic geometry of the ×2 structure of this layer, its optical response should be described by a complex dielectric tensor, with a component perpendicular to the substrate surface and two components parallel to it, one being along the long dimension of the NRs and the other one along the short dimension. Moreover, it has been shown by x-ray diffraction that the formation of the NRs is associated with a reconstruction of the Ag surface beneath the Si layer [7], with two missing Ag rows per ×2 unit cell. Such reconstruction is expected to have some influence on the reflectance of Ag.…”

“…However, these observations have recently been reconsidered. Scanning tunneling microscopy (STM) and grazing incidence x-ray diffraction (GIXD) experiments have shown that the honeycomb model computed by DFT is not adapted since the Ag(110) exhibits a missing-row reconstruction upon Si adsorption [7]. At the same time, another experimental study concluded that the honeycomb structure observed by STM on Si/Ag(110) was due to tip artifacts [8], and a theoretical study of the electronic structure of Si/Ag(110) and Si/Ag(111) showed that the conical features visible in ARPES measurements are not due to silicon but to the silver substrate, as an effect of band folding induced by the Si overlayer periodicity [9].…”

“…These self-assembled nanoribbons (SANRs) cover the entire surface at a full coverage (FC) corresponding to 0.8 monolayer (ML), where 1 ML corresponds to the Ag(110) surface atom density, i.e. 8.45 atoms/nm 2 [7]. For higher coverages, the ×2 reconstruction is progressively replaced by a c(8×4) superstructure (denoted hereafter "×4") [8].…”