Revealing the electronic structure of silicon intercalated armchair graphene nanoribbons by scanning tunneling spectroscopy

The electronic properties of graphene nanoribbons grown on metal substrates are significantly masked by the ones of the supporting metal surface. Here, we introduce a novel approach to access the frontier states of armchair graphene nanoribbons (AGNRs). The in situ intercalation of Si at the AGNR/Au(111) interface through surface alloying suppresses the strong contribution of the Au(111) surface state and allows for an unambiguous determination of the frontier electronic states of both wide and narrow band gap AGNRs. First-principles calculations provide insight into substrate induced screening effects, which result in a width-dependent band gap reduction for substrate-supported AGNRs. The strategy reported here provides a unique opportunity to elucidate the electronic properties of various kinds of graphene nanomaterials supported on metal substrates.This work has been supported by the Swiss National Science Foundation, the Office of Naval Research BRC program, and the European Commission Graphene Flagship (No. CNECT-ICT-604391). C.S.S. is grateful to Ministerio de Economía y Competitividad for financial support via the Juan de la Cierva Incorporación Grant (IJCI-2014-19291, cofunded by the European Investment Bank)