Edge states in the honeycomb reconstruction of two-dimensional silicon nanosheets

Electrons confined within a two-dimensional (2D) honeycomb potential can host localized electronic states at their edges. These edge states exhibit distinctive electronic properties relative to the bulk and may result in spin polarization or topologically protected conduction. However, the synthesis and characterization of well-defined 2D structures which host such edge states remain challenging. Here, we confirm the presence of a two-dimensional electron gas (2DEG) and find evidence for unique edge states in the Ag-induced honeycomb surface reconstruction of silicon nanosheets (SiNSs) grown on Ag(111). Atomic-scale scanning tunneling microscopy and computational modeling confirm that the electronic properties of the SiNS surface are determined by the honeycomb surface reconstruction. This surface presents ordered edge terminations with distinct spectroscopic signatures associated with the edge orientation, and calculations suggest that Rashba-type spin-orbit coupling may result in spin-polarized conduction along certain edge orientations. This quantification of the electronic structure of edge states in SiNS 2DEGs will address ongoing efforts to engineer quantum effects in silicon-based nanostructures.