  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.

Materials Science