Experimental and theoretical determination of {\sigma}-bands on ("2$\sqrt{3}$x2$\sqrt{3}$") silicene grown on Ag(111)

Abstract

Silicene, the two-dimensional (2D) allotrope of silicon has very recently attracted a lot of attention. It has a structure that is similar to graphene and it is theoretically predicted to show the same kind of electronic properties which has put graphene into the focus of large research and development projects world-wide. In particular, a 2D structure made from Si is of high interest because of the application potential in Si-based electronic devices. However, so far there is not much known about the silicene band structure from experimental studies. A comprehensive study is here presented of the atomic and electronic structure of the silicene phase on Ag(111) denoted as (2$\sqrt{3}$x2$\sqrt{3}$)R30{\deg} in the literature. Low energy electron diffraction (LEED) shows an unconventional rotated ("2$\sqrt{3}$x2$\sqrt{3}$") pattern with a complicated set of split diffraction spots. Scanning tunneling microscopy (STM) results reveal a Ag(111) surface that is homogeneously covered by the ("2$\sqrt{3}$x2$\sqrt{3}$") silicene which exhibits an additional quasi-periodic long range ordered superstructure. The complex structure, revealed by STM, has been investigated in detail and we present a consistent picture of the silicene structure based on both STM and LEED. The homogeneous coverage by the ("2$\sqrt{3}$x2$\sqrt{3}$") silicene facilitated an angle-resolved photoelectron spectroscopy study which reveals a silicene band structure of unprecedented detail. Here, we report four silicene bands which are compared to calculated dispersions based on a relaxed (2$\sqrt{3}$x2$\sqrt{3}$) model. We find good qualitative agreement between the experimentally observed bands and calculated silicene bands of {\sigma} character.