Unoccupied Electronic States Of 2d Si On Ag-Root 3-Si(111)

Optimizing substrate characterization to grow 2D Si layers on surfaces is a major issue toward the development of synthesis techniques of the promising silicene. We have used inverse photoemission spectroscopy (IPES) to study the electronic band structure of an ordered 2D Si layer on the root 3 x root 3-Ag/Si(111) surface (root 3-Ag). Exploiting the large upwards band bending of the root 3-Ag substrate, we could investigate the evolution of the unoccupied surface and interface states in most of the Si band gap. In particular, the k(parallel to)-dispersion of the root 3-Ag free-electron-like S-1 surface state measured by IPES, is reported for the first time. Upon deposition of similar to 1 ML Si on root 3-Ag maintained at similar to 200 degrees C, the interface undergoes a metal-insulator transition with the complete disappearance of the S-1 state. The latter is replaced by a higher-lying state U-0 with a minimum at 1.0 eV above E-F. The origin of this new state is discussed in terms of various Si 2D structures including silicene.