Structure of Silicene Grown on Ag(111)

The structure of silicene, the two-dimensional honeycomb sheet of Si, grown on Ag(111) was investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) combined with density functional theory (DFT) calculation. Two atomic arrangements of honeycomb configuration were found by STM, which are confirmed by LEED and DFT calculations; one is $4{\times}4$ and the other is $\sqrt{13}{\times}\sqrt{13}$ R13.9°. In the $4{\times}4$ structure, the honeycomb lattice remains with six atoms displaced vertically, whereas the $\sqrt{13}{\times}\sqrt{13}$ R13.9° takes the regularly buckled honeycomb geometry.