Formation of graphene-capped cobalt silicides

Abstract

Intercalation synthesis of graphene-capped cobalt silicides has been studied in situ by core-level photoelectron spectroscopy with synchrotron radiation and low-energy electron diffraction. It is found that at 400 °C the intercalation of graphene/Ni(1 1 1) with cobalt takes place in a wide range of coverage up to 17 ML Co. Graphene is strongly coupled with the upper layer of Co atoms and stabilizes the fcc structure of the intercalated Co(1 1 1) film. Subsequent intercalation of graphene/Co/Ni(1 1 1) with silicon results in the formation of an ordered Co3Si surface phase of the (√3 × √3)R30° structure and then of Co2Si silicide and Co-Si solid solution. Our experimental data and DFT calculations have shown that the coupling between the graphene layer and the surface silicide is rather weak and the properties of quasi-freestanding graphene are preserved.