Spectroscopic Identification of Ag-Terminated "Multilayer Silicene" Grown on Ag(111)

The electronic structure of the outermost layer of "multilayer silicene" was investigated by metastable atom electron spectroscopy (MAES). It is usually difficult to elucidate the electronic structure of an ultrathin film grown on a solid substrate excluding the contribution from the substrate, especially such as "multilayer silicene" grown on a Ag(111) substrate. MAES used in this study thus provides a proper solution because the excitation source, He∗(2³S) atom, cannot penetrate through the first layer. Comparing the MAES spectra of "multilayer silicene" and of the Si(111)√3 x √3-Ag surface where the Ag atoms are arranged to form a superlattice on the (111) surface of the Si diamond crystal, we find that these spectra are essentially identical to each other. This result indicates that the so-called "multilayer silicene" is actually not multilayered, i.e., a stack of honeycomb lattice layers. (Graph Presented).