A comprehensive study of the (2√3  ×  2√3)R30° structure of silicene on Ag(1 1 1)

Abstract

Abstract. The deposition of one silicon monolayer on Ag(111) gives rise to a set of superstructures depending on growth conditions. These superstructures are correlated to the epitaxy between the honeycomb structure of silicon (so called silicene) and the silver substrate.In this paper, from a detailed re-analysis of experimental results, obtained by Scanning Tunneling Microscopy and by Low Energy Electron Diffraction on the (2√3x2√3)R30° structure, we propose a new atomic model of the silicene layer based on periodic arrangements of perfect areas of (2√3x2√3)R30° surrounded by defect areas. A generalization of this model explains the main experimental observations: deviation of the average direction, Moiré patterns and apparent global disorder. In the frame of the proposed model, the apparent disorders observed on the STM images, would be topological effects, i.e. the silicene would keep a quasi-perfect honeycomb structure.

Band structure of hydrogenated silicene on Ag(111): Evidence for half-silicane

“…Between the bright regular honeycombs there are distorted honeycombs. Both the regular and the distorted honeycombs have very consistently been reported in the literature for ("2 √ 3 × 2 √ 3") silicene [16,17]. Our previous work [8] confirms that this silicene phase covers the whole surface with a specific buckling for which only 2 out of the 14 Si atoms per (2 √ 3 × 2 √ 3) unit cell are observed by STM.…”

Point defects in epitaxial silicene on Ag(111) surfaces

“…Finally, we discuss the mysterious 2 3 × 2 3 silicene based on our results, though there is now some uncertainty and debate on this phase [66][67]. The concentration of Si-SW defects in 2 3 × 2 3 and 13 × 13 silicene are in the same order of magnitude, thus it is also hard to find Si-SW defects in 2 3 × 2 3 silicene.…”

“…Hence we did not see prominent absence of bright points in the experimental STM image, but we did observe large number of warped hexagon (Figure 4c), which may originate from the large concentration of Si-DV. Recently, a geometry model of 2 3 × 2 3 silicene was proposed, in which silicene layer is based on periodic arrangements of perfect areas of 2 3 × 2 3 silicene surrounded by defect areas on a rigid lattice of silver [67]. In that model, the warped hexagons observed in experimental STM image are ascribed to local relaxation of strain during epitaxial growth rather than point defects.…”

A comprehensive analysis of the (√13 × √13)R13.9° type II structure of silicene on Ag(1 1 1)

“…In this paper, starting with an experimental STM image at high resolution, we develop an equivalent model for the (13x13)R±13.9° structure. In contrary to the (23x23)R30° structure, the (13x13)R±13.9° structure is strained in expansion relative to silver (see table 1 of [14]). A generalization of this model explains more accurately most of the STM images found in the literature: Moiré-like patterns and apparent global disorders.…”