Growth of silicene layers on Ag(111): unexpected effect of the substrate temperature

The deposition of one silicon monolayer on the silver (111) substrate in the temperature range 150-300 degrees C gives rise to a mix of (4 x 4), (2 root 3 x 2 root 3) R30 degrees and (root 13 x root 13) R13.9 degrees superstructures which strongly depend on the substrate temperature. We deduced from a detailed analysis of the LEED patterns and the STM images that all these superstructures are given by a quasi-identical silicon single layer with a honeycomb structure (i.e. a silicene-like layer) with different rotations relative to the silver substrate. The morphologies of the STM images are explained from the position of the silicon atoms relative to the silver atoms. A complete analysis of all possible rotations of the silicene layer predicts also a (root 7 x root 7)R19.1 degrees superstructure which has not been observed so far.